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A cohort of a heretofore not described rare subtype of renal oncocytoma, small cell oncocytoma with pseudorosettes is presented. Patients were 6 women and 4 men with ages ranging from 51 to 76 years. The tumors displayed areas composed of small cells ("oncoblasts") featuring scant cytoplasm and small, round monomorphic nuclei. The small cell areas constituted 15% to 60% of the total tumor volume (mean, 28.5%; median, 22.5%). No necrosis or mitotic activity was discerned. All tumors also contained areas composed of characteristic oncocytes comprising 40% to 85% of the total tumor volume. In all cases, a varying number of pseudorosettes were identified. The pseudorosettes were composed of small globules of (periodic acid-Schiff-positive) hyaline basal membrane-like material surrounded by small "oncoblastic" cells. The immunohistochemical profile was variable, including at least focal positivity for AE1-3 (10/10), cytokeratin 7 (7/10), epithelial membrane antigen (10/10), c-kit (6/10), antimitochondrial antigen (MIA;10/10), PAX-2 (9/10), AMACR (racemase;6/10), CD10 (5/10), parvalbumin (8/10), vimentin (6/10), claudin 7 (10/10), and claudin 8 (3/10). No immunoreactivity for carbonic anhydrase 9, HMB-45, S-100A1, and TFE3 was documented. We found no differences in the immunophenotype in the small cell oncocytes/oncoblasts that formed pseudorosettes and those that did not. However, there were differences in the immunohistochemical profile of classic oncocytes and small cell oncocytes/oncoblasts. Using array comparative genomic hybridization, no chromosomal changes were identified in any of the cases examined (n = 3). No numerical changes of chromosomes 7 and 17 were revealed on fluorescence in situ hybridization analysis (n = 3). In conclusion, we herein present the first study on small cell renal oncocytomas with formation of pseudorosettes. This is a rare subtype of oncocytoma, which may, especially on a core biopsy, present differential diagnostic difficulties. The immunohistochemical profile of these tumors is variable and differs in significant respects from that of conventional renal oncocytoma. Awareness of this entity and its immunohistochemical variability should help in distinguishing this rare tumor from malignant tumors with similar (small cell) histomorphologic features. All tumors behaved in a benign fashion during follow-up (mean, 3.1 years; median, 1 year).

Recently, renal angiomyoadenomatous tumor (RAT) has been identified. However, there are no descriptions about clear cell renal cell carcinoma (RCC) with focal RAT-like features. A 33-year-old Japanese man was found to have a tumor in the left kidney. Macroscopically, the tumor extended into the perinephric fat tissue, and the cut surface showed the yellowish color. The histologic examination of the tumor consisted of 2 components of clear cell RCC and RAT-like area. The RAT-like area showed the admixture of epithelial cells with basophilic or clear cytoplasm and stromal component containing leiomyomatous stroma, fine capillary network, and pericytic network. Immunohistochemically, epithelial neoplastic cells in RAT-like area were diffusely positive for CD10 and RCC Ma. G-band karyotype showed the structural abnormality of chromosome 3 and both components of clear cell RCC and RAT-like area revealed the identical VHL gene mutation. Finally, pathologists should pay attention to the presence of clear cell RCC focally resembling RAT.

S100A1 is a calcium-binding protein and a member of the S100 family. Recently, S100A1 immunohistochemistry may be an available marker in the differential diagnosis between renal oncocytoma and chromophobe renal cell carcinoma (RCC). However, there are no reports on S100A1 expression in oncocytic papillary RCC that has been recently identified. In this article, we immunohistochemically examined the expression of S100A1 protein in 18 renal tumors including 4 renal oncocytoma, 10 chromophobe RCCs, and 4 oncocytic papillary RCCs. All the cases of renal oncocytoma and oncocytic papillary RCC showed a positive reaction for S100A1 with cytoplasmic pattern. In chromophobe RCC, 3 of 4 tumors with typical variant and 4 of 6 tumors in eosinophilic variant were completely negative for S100A1. Finally, S100A1 immunohistochemistry may be useful in distinguishing renal oncocytoma from chromophobe RCC, but it may be of no use in the differential diagnosis between renal oncocytoma and oncocytic papillary RCC.

Translocation-type renal carcinoma has been recently discovered, and it is possible that this tumor may have been previously diagnosed as other types of renal tumor. We have subjected 41 renal tumors, including VHL gene mutation-negative clear cell renal cell carcinoma (RCC), papillary RCC, and chromophobe RCC, to immunohistochemistry of transcription factor E3 (TFE3) and TFEB. All tumors were histologically evaluated by additional immunohistochemical study. As a result, 5 tumors showed a positive reaction for TFE3 with a range from 1+ to 2+ in intensity. No tumors were positive for TFEB. In 5 tumors immunohistochemically positive for TFE3, chimeric transcripts including ASPL-TFE3, PRCC-TFE3, CLTCTFE3, PSF-TFE3, or Nono-TFE3 were not detected. The diagnosis of 6 tumors was changed by reevaluation through retrospective histological and immunohistochemical study. In 4 of 6 tumors, the diagnosis of clear cell RCC was changed to chromophobe RCC. In 1 tumor, oncocytoma was detectable, and RCC with rhabdoid features and sarcomatoid changes was detected in 1 tumor. Finally, the cutoff value of TFE3 immunohistochemistry should be more than 2+ with a wide range. The translocation-type renal carcinoma seems to be quite rare.

Epithelioid angiomyolipomas (perivascular epithelioid cell tumors) of the kidney are defined as potentially malignant mesenchymal lesions that are closely related to classic angiomyolipoma. Although approximately 120 cases are published, mostly as case reports with variably used diagnostic criteria, the pathologic prognostic predictors of outcome are unknown. We analyzed the clinicopathologic parameters in a large series of 41 cases of pure epithelioid angiomyolipomas of the kidney, which we designate as pure (monotypic) epithelioid PEComas to contrast them from classic angiomyolipomas that are regarded by some as PEComas. We use the terminology "pure" to separate these cases from those that may have variable epithelioid components. The mean age of the patients was 40.7 years (range, 14 to 68 y). The male-to-female ratio was 1:1. Seventy-nine percent of patients were symptomatic at presentation with metastatic disease at onset in 12 cases. Follow-up and/or disease progression information were available for 33 of 41 cases (mean, 44.5 mo and median, 24.5 mo; range, 4 to 240); 9 patients had a history of associated tuberous sclerosis. Recurrence and metastasis were seen in 17% and 49% of patients; 33% of patients died of disease. Lymph node involvement was seen in 24% of patients; the liver (63%), lung (25%), and mesentery (18.8%) were the most common metastatic sites. Clinicopathologic parameters associated with disease progression (recurrence, metastasis, or death due to disease) in univariate analysis included associated tuberous sclerosis complex or concurrent angiomyolipoma (any metastasis, P=0.046), necrosis (metastasis at diagnosis, P=0.012), tumor size >7 cm (progression, P=0.021), extrarenal extension and/or renal vein involvement (progression, P=0.023), and carcinoma-like growth pattern (progression, P=0.040) (the 5 adverse prognostic parameters for pure epithelioid PEComas). Tumors with

Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion recently has been found. In this article, we demonstrate an unusual features of such a case. A 73-year-old Japanese woman presented with macroscopic hematuria. The imaging examinations disclosed the renal tumor. Histological examination showed the finding of ASPL-TFE3 RCC, which was characterized by papillary, alveolar, or solid growth of voluminous cell with clear and eosinophilic cells, and stromal psammoma body and hyaline nodules. Additionally, shrunken nuclei, thick cell border, and perinuclear clearing characteristic of chromophobe renal cell carcinoma were observed in the alveolar growth area and the transitional zone between stromal hyalinization, and osseous metaplasia was identified. Immunohistochemically, nuclei of tumorous cell were diffusely positive for TFE3. A RT-PCR study revealed the ASPL-TFE3 chimeric transcript. Finally, pathologists should recognize that the histology of RCC associated with Xp11.2 translocation/TFE3 gene fusion may focally resemble that of chromophobe RCC, but TFE3 immunohistochemistry and molecular genetic study may be helpful in the differential diagnosis. Moreover, osseous metaplasia as well as psammoma bodies should be added to the histological spectrum of the stromal change in RCC associated with Xp11.2 translocations/TFE3 gene fusions.

Hybrid oncocytic/chromophobe tumors (HOCT) of the kidney have been described in patients with Birt-Hogg-Dubé syndrome (BHD) and in association with renal oncocytosis without BHD. HOCT in patients without evidence of BHD or renal oncocytosis is exceedingly rare, and these cases have been poorly characterized. We have identified and studied 14 cases of HOCT from previously diagnosed renal oncocytomas (398 cases) and chromophobe renal cell carcinomas (351 cases) without evidence of BHD or renal oncocytosis. Immunohistochemical, ultrastructural, and molecular genetic studies analyzing numerical chromosomal changes, loss of heterozygosity for chromosome 3p, and mutation status of VHL, c-kit, PDGFR, and folliculin (FLCN) genes were performed. HOCTs were identified in nine men and five women (age range 40-79 years). The size of tumors ranged from 2 to 11 cm. All tumors displayed a solid alveolar architecture and were composed of cells with abundant granular eosinophilic oncocytic cytoplasm with perinuclear halos. Occasional binucleated neoplastic cells were present, but irregular, hyperchromatic, wrinkled (raisinoid) nuclei were absent. The cytoplasm contained numerous mitochondria of varying sizes, but only sparse microvesicles with amorphic lamellar content were found. Tumors were positive for CK7 (12/14), AE1-AE3 (14/14), anti-mitochondrial antigen (14/14), E-cadherin (11/13), parvalbumin (12/14), and epithelial membrane antigen (14/14). Tumors were generally negative for racemase, CK20, CD10, and carboanhydrase IX. Interphase fluorescence in situ hybridization revealed multiple chromosomal losses and gains with a median of four (range 1-9) chromosomal aberrations per case. Monosomy of chromosome 20 was common and found in 7 of 14 cases. Monosomy of chromosomes 6 and 9 was present in 4 of 14 cases each, of which two cases displayed monosomy for both chromosomes 6 and 9. Polysomy of chromosomes 10, 21, and 22 was found in 4/14 cases each, of which one case displayed polysomy for all these three chromosomes. No pathogenic mutations were found in the VHL, c-kit, PDGFR, and folliculin (FLCN) genes. (1) We have shown that hybrid oncocytic/chromophobe tumors of the kidney do occur, albeit rarely, outside the Birt-Hogg-Dubé syndrome and without associated renal oncocytosis. (2) These tumors constitute a relatively homogenous group with histomorphologic features of both chromophobe renal cell carcinoma and renal oncocytoma. (3) Sporadic hybrid oncocytic/chromophobe renal tumors are characterized by multiple numerical aberrations (both mono- and polysomies) of chromosomes 1, 2, 6, 9, 10, 13, 17, 21, and 22 and lack of mutations in the VHL, c-kit, PDGFRA, and FLCN genes. (4) The tumors seem to behave indolently as no evidence of malignant behavior was documented in our series, although admittedly, the follow-up was too short to fully elucidate the biological nature of this rare neoplasm. At worst, these tumors could have a low malignant potential, which only can be found out with longer follow-up.

Aim: The purpose of this study was to investigate the Prostate Health Index as a marker for tumor aggressiveness in prostate biopsy and the optimization of indication for treatment options. Methods: Our cohort consisted of 320 patients indicated for radical prostatectomy with preoperative measurements of total prostate-specific antigen, free prostate-specific antigen, [-2]proPSA, calculated %freePSA, and Prostate Health Index. The Gleason score was determined during biopsy and after radical prostatectomy. Using the Gleason score, we divided the group of patients into the 2 subgroups: Gleason score ≤6 and Gleason score >6. This division was performed according to the biopsy Gleason score and according to the postoperative Gleason score. We compared total prostate-specific antigen, [-2]proPSA, %freePSA, and Prostate Health Index in the subgroups Gleason score ≤6 and Gleason score >6 after biopsy and the definitive score. Results: On evaluation of the subgroups created by Gleason score ≤6 and Gleason score >6, we observed agreement between biopsy Gleason score and definitive Gleason score in only 45.3% of cases. Of the calculated biopsy, Gleason score ≤6 and Gleason score >6 subgroups, [-2]proPSA, and Prostate Health Index (P = .0003 and P = .0005) were statistically significant. Of the definitive Gleason score ≤6 and Gleason score >6 subgroups, Prostate Health Index, [-2]proPSA, %freePSA, and PSA (P < .0001, P < .0001, P = .0003, and P = .0043) were statistically significant. The best area under the curve value (0.7496) was achieved by Prostate Health Index when the subgroups were established according to the postoperative Gleason score. Conclusion: Prostate Health Index is the best of the tested markers for the categorization of Gleason score 6 tumors and for facilitating the management of patients with prostate cancer. Prostate Health Index can be a helpful marker for indication of active surveillance or radical prostatectomy. Prostate health index can also simplify the decision of whether to perform nerve-sparing radical prostatectomy.

Few genetic studies of renal carcinoid tumor have been conducted thus far. We performed immunohistochemical and genetic examinations on four renal carcinoid tumors. Histologically, the tumors consisted of neoplastic cells with round to oval nuclei. Various growth patterns such as tightly packed cords and trabeculae, ribbon-like, trabecular, sheet-like or solid growth were observed. Nuclear chromatin showed a coarse and granular pattern. Immunohistochemically, tumors were positive for chromogranin A and synaptophysin. In the fluorescence in situ hybridization study, three of four tumors revealed monosomy of chromosome 3 (D3Z1), but one tumor showed monosomy of chromosome 13 (D13S319/13q34). Using PCR amplification and fragment analysis of three microsatellite markers (D3S1300, D3S666 and D3S1768) of chromosome arm 3p, one tumor showed loss of heterozygosity at D3S1300 and D3S1768, one tumor was not informative and the analysis of two tumors failed due to low DNA quality. In three cases, the VHL gene status was tested. Two tumors showed wild-type, but the analysis of one tumor failed to provide adequate results. In conclusion, we suggest that the abnormality of chromosome 3 is involved in the pathogenesis of renal carcinoid tumor.

Background In a randomized study, we observed a higher incidence of biopsy-proven acute rejection with preemptive valganciclovir therapy as compared with valacyclovir prophylaxis for prevention of cytomegalovirus (CMV) disease after renal transplantation (RTx). Persistence of the virus within the allograft could stimulate the alloimmune response. The aim of our study was to evaluate intragraft CMV infection in patients randomized to the trial. Methods RTx recipients at risk of CMV were randomized to pre-emptive therapy with valganciclovir ( n=36) for significant CMV viraemia (≥2,000 copies/ml by quantitative PCR in whole blood samples) or 3-month prophylaxis with valacyclovir ( n=34). Renal biopsies performed during 12 months post-RTx were analysed for the presence of CMV by real-time PCR and immunohistochemical staining. Results A total of 35 patients (59 biopsies) in the pre-emptive group and 31 patients (57 biopsies) with valacyclovir prophylaxis had ≥1 biopsy specimen with sufficient material for intragraft CMV determination. Cumulative incidence of intragraft CMV infection was 14% and 7% ( P=0.315) with pre-emptive therapy and prophylaxis, respectively. Patients at risk for primary CMV infection (CMV serological donor-positive and recipient-negative) were at higher risk for intragraft CMV infection (40% versus 5%; P=0.008). CMV viraemia at the time of biopsy was associated with the presence of CMV within the allograft ( PConclusions During the first year after RTx, the incidence of intragraft CMV infection was relatively low with comparable rates in patients managed by pre-emptive valganciclovir therapy and valacyclovir prophylaxis.

Modern chemotherapy combined with surgery can achieve complete cure in over 90% of all patients with malignant testicular germ cell tumors. Even tumors that have already metastasized at the time of orchidectomy are curable by platinum-based multidrug treatment. Chemotherapy related changes can be seen in the residual tumor tissue in metastatic sites. In patients fully responding to chemotherapy these changes include complete necrosis of the tumor cells, and inflammatory-phagocytic response, fibrosis replacing the necrotic tumor tissue, and residual benign somatic tissue tissues in form of teratoma. Epithelial and stromal cells of these teratomas may display nuclear atypia, which is however not a reason for concern and should not be considered an indication for additional chemotherapy. Less commonly the lymph nodes contain cystic trophoblastic tumors. In contrast to metastatic classical biphasic or monophasic choriocarcinoma, cystic trophoblastic tumors portend a favorable clinical outcome. Patients with an incomplete response to chemotherapy and those with recurrences of the malignant tumor contain in metastatic sites foci composed of embryonal carcinoma cells, yolk sac carcinoma, or choriocarcinoma. The latter two subtypes of germ cell neoplasia may recur in several microscopic variant forms. Somatic forms of malignancy (also known as "non-germ cell malignancies") that develop occasionally in some treated patients include most often sarcomas and tumors resembling central primitive neuroectodermal neoplasms. These secondary malignancies are usually resistant to chemotherapy. The broad spectrum of morphologic findings in the lymph nodes of patients with treated metastatic testicular germ cell tumors clearly illustrates the importance of meticulous pathologic analysis of tissue changes related to chemotherapy.

Background. Cytomegalovirus (CMV) is a risk factor for acute renal allograft rejection. The aim of this study was to determine the impact of CMV viremia on subclinical rejection (SCR) and interstitial fibrosis and tubular atrophy (IF/TA) in protocol biopsy at 3 months after transplantation. Methods. A total of 118 consecutive renal transplant recipients at risk for CMV (donor and recipient CMV seropositive) were included and followed up prospectively. Protocol biopsies with sufficient tissue were obtained in 102 patients. CMV activity was monitored using real-time polymerase chain reaction in whole blood. Three-month prophylaxis with valacyclovir or ganciclovir was given in 60 patients, whereas the remaining 42 patients were managed by preemptive therapy. Multivariate logistic stepwise regression analysis was used to estimate the effect of CMV viremia and other covariates on SCR and IF/TA. Results. CMV viremia occurred in 41% of the patients with a median peak viral load of 1300 copies/mL. The incidence of SCR and IF/TA was 29% and 28%, respectively. CMV viremia was not a risk factor for SCR (OR=0.77, P=0.551); however, viremia of more than or equal to 2000 copies/mL increased the risk of IF/TA (OR=3.83, P=0.023). Biopsyproven acute rejection (OR=3.34, P=0.009) and sirolimus-based immunosuppression (OR=6.13, P=0.008) were independent predictors of SCR. Delayed-graft function (OR=6.02, P=0.001) and donor age (OR=1.53 per 10-year increase, P= 0.009) were associated with IF/TA. Conclusions. CMV viremia is not an independent risk factor for SCR. CMV viremia with viral load of more than or equal to 2000 copies/mL is associated with increased risk of IF/TA in protocol biopsy at 3 months after transplantation.

Background Adult-onset renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion is a very rare tumor. To date, there are no reports on immunocytochemical study of the primary tumor. We describe such a case that we diagnosed by immunocytochemistry of imprint cytology material. Case A 46-year-old man was found to have a mass in the lower pole of the right kidney. Magnetic resonance imaging (MRI) T2-weighted images showed a hypointense area in the tumor, and papillary RCC was suspected. Imprint cytology showed tumor cells that were isolated or arranged in large or small papillary clusters. Irregularly shaped large oval nuclei, finely granular chromatin and a single large nucleolus were noted. Cytoplasm was abundant and admixed with clear and granular eosinophilic patterns and scattered large vacuolated cells. Almost all tumor cells diffusely expressed immunocytochemical reactivity to TFE3 protein. Hyaline nodules were observed in the stroma. Ultrastructurally, neoplastic cells contained rhomboid crystals identical to those of alveolar soft part sarcoma. Conclusion The immunocytochemistry of TFE3 protein may be a powerful tool for accurate diagnosis when RCC associated with Xp11.2 translocation/TFE3 gene fusion is suspected by imprint cytology even in adult-onset cases, and cytotechnologists should accurately recognize cytologic findings of this tumor.

Chromophobe renal cell carcinoma (RCC) is subdivided into typical and eosinophilic variants. We report such two cases with focus on imprint cytology and fluorescence in situ hybridization (FISH). The first case is a 53-year-old Japanese man and the second is a 76-year-old Japanese man. Histologically, the diagnosis of typical and eosinophilic variants of chromophobe RCC was suspected. In imprint cytology, irregularity of nuclear membrane, binucleation, perinuclear halo, and thick cell border were observed. Immunohistochemically, neoplastic cells of both tumors were positive for cytokeratin 7, E-cadherin, c-kit, and CD10. In FISH study, both tumors revealed the monosomy of chromosomes 10 and 21. Additionally, FISH study in eosinophilic variant of chromophobe RCC showed the disomy of chromosomes 7 and 17. In conclusion, we suggest that the combination study of imprint cytology and FISH of chromosomes 10 and 21 as well as routine histology may contribute to the accurate diagnosis of chromophobe RCC.

Summary Normal medullary interstitial cells regulate blood flow, water and salt absorption, and ultimately blood pressure through synthesis and secretion of prostanoids in which cycloxygenases play the rate-limiting steps. We found that most renomedullary interstitial cell tumors overexpressed cycloxygenase-2 (COX-2), with concomitant expression of microsomal prostaglandin E synthase-1 and the receptor for prostaglandin E2. Prostaglandin E2 is the major prostaglandin product of COX-2/microsomal prostaglandin E synthase-1 enzymatic pathway in medullary interstitial cells, and concomitant expression of COX-2, microsomal prostaglandin E synthase-1, and prostaglandin E2 receptor on interstitial cell tumors implies the presence of an autocrine growth loop important in pathogenesis of these tumors. Furthermore, overexpression of COX-2 protein was observed in association with homozygosity in several polymorphic sites within COX-2 gene (promoter region sites −1186 T/T and −765 G/G, intron 5 IVS5-275 T/T, and exon 10 Ex10+837 T>C), indicating their role in development of these tumors.

The nature of tubulocystic carcinoma, a rare renal tumor composed of tubular and cystic structures, is poorly understood. It has been suggested that it may represent a low-grade collecting duct carcinoma of the kidney despite the lack of sufficient molecular and pathologic evidence. The aim of this study was to examine the clinical and pathologic features of 13 cases of tubulocystic carcinoma of the kidney. Furthermore, using gene expression microarray analysis, we defined the molecular signature of this tumor by comparing it with other renal tumors in our previously established molecular profile database. Histologically, all 13 tumors were composed of closely packed tubules and cysts of varying sizes separated by fibrovascular septa. The epithelial lining cells of the tubules and cysts in this tumor were characterized by abundant eosinophilic cytoplasm with prominent nucleoli often showing a hobnail appearance. Clinically, one of the 13 cases showed metastasis to the pelvic lymph nodes. Five of the 13 cases coexisted with papillary renal cell carcinoma (RCC) (n=3) or papillary adenoma (n=2). In addition, the molecular profile of tubulocystic carcinoma was similar but not identical to those of papillary RCC by clustering analysis. Through comparative genomic microarray analysis, tubulocystic carcinoma showed gains of chromosome 17, but not chromosome 7, whereas most papillary RCCs showed chromosomal gains in both 7 and 17 (trisomies). Therefore, based on its unique pathologic features and molecular signature as well as its biologic behavior to develop metastasis either by itself or in association with papillary RCC, tubulocystic carcinoma of the kidney should be recognized as a distinct subtype of RCC and be distinguished from other malignant and benign cystic lesions of the kidney.

We attempted to investigate the clinicopathological correlation of renal oncocytoma (RO) with renal vein extension. We identified seven ROs with extension into the branches of renal vein. The age of seven patients ranged from 61 to 82 years. Five cases were identified incidentally; two patients had gross hematuria. After surgery, all patients were alive and free of tumors with follow-up of 1 to 5 years (mean = 3.6). Oncocytomas measured from 2.2 to 7.5 cm. Renal vein extension was grossly suspected in five of seven cases and histologically confirmed in all seven cases. Tumor cells were positive for cytokeratins, mitochondrial-antigen (MIA), epithelial membrane antigen (EMA), and parvalbumin; five of seven tumors were focally positive for CD117. Ultrastructurally, the cytoplasm was packed by mitochondria. Molecular genetic analysis did not detect abnormal numbers of chromosomes 1, 2, 6, 7, 10, 17, and XY by fluorescence in situ hybridization, loss of heterozygosity on 3p and mutation of von Hippel-Lindau gene in all cases. Array comparative genomic hybridization analysis of two cases did not show any major genetic changes. Our conclusions are as follows: (1) renal oncocytomas may have intravascular extension to the branches of the renal vein; (2) renal oncocytomas with intravascular extension to the branches of the renal vein have the same morphological, immunohistochemical, and cytogenetic findings as have their counterparts without evidence of intravascular invasion; (3) the absence of metastases suggests an overall benign behavior of this tumor, but this has to be substantiated by further studies with a long-term follow-up; and (4) in a renal tumor with granular cytoplasm showing renal vein extension, it is necessary to carefully exclude renal cell carcinomas such as chromophobe RCC, oncocytic variant of papillary RCC, and granular variant of clear cell RCC.

Carcinoid tumor of the renal pelvis is an extremely rare neoplasm and only two cases have been previously reported in the English-language literature. Reported herein is a third case of carcinoid tumor arising in the renal pelvis. The tumor extending from the left renal pelvis into the left kidney was incidentally found in a 55-year-old Japanese woman. Macroscopically, the tumor was predominantly located in the dilated renal pelvis and was grayish-white on cut surface. Microscopically, neoplastic cells proliferated with a ribbon-like, trabecular, tubular and solid pattern. Furthermore, the tumor focally invaded the kidney parenchyma. No precursor lesion of neuroendocrine tumor was observed in the peripheral urothelial epithelium. Neither urothelial carcinoma nor teratoma component was observed within the tumorous mass. The cytoplasm of neoplastic cells was focally positive for Grimelius stain and focally positive for chromogranin A and synaptophysin. However, no neoplastic cells reacted with cytokeratins 7 and 20. Ultrastructurally, neoplastic cells contained dense core granules in the cytoplasm. Urologists and pathologists should recognize that carcinoid tumor may arise from the renal pelvis.

We evaluated the utility of SDS-PAGE/Western blot and CE coupled with MS (CE-MS) for detection of urinary polypeptide biomarkers of renal disease in patients with IgA-associated glomerulonephritides. In a reference cohort of 402 patients with various renal disorders and 207 healthy controls, we defined CE-MS patterns of renal damage and IgA nephropathy (IgAN). In a blinded analysis of a separate cohort of patients with IgAN (n = 10), Henoch-Schoenlein purpura (HSP) with nephritis (n = 10), and IgA-associated glomerulonephritis due to hepatitis C virus (HCV)-induced cirrhosis (n = 9), and healthy controls (n = 12), we compared SDS-PAGE/Western blot and CE-MS against clinical urinalysis for detection of urinary proteins/polypeptides. Urinalysis indicated proteinuria for 50, 90, and 33% of patients, respectively, and for none of the healthy controls. SDS-PAGE/Western blot showed urinary polypeptides abnormality for 90, 80, and 67% of patients, respectively, and for none of the healthy controls. CE-MS indicated a Renal Damage Pattern in 80, 80, and 100 of patients, respectively, and in 17% of healthy controls, with the more specific IgAN Pattern in 90, 90, and 1%, respectively, and in none of the healthy controls. Based on differences in CE-MS patterns, the disease mechanisms may differ among various IgA-associated glomerulonephritides. These exploratory findings should be evaluated in a prospective study with contemporaneous renal biopsy and urinary testing. If validated, it may be feasible to adapt the CE-MS methodology to develop novel tests to detect renal injury at earlier stages, assess clinical manifestations, and monitor responses to therapy in patients with IgA-associated renal diseases.

Renal angiomyoadenomatous tumor has been described in 2000, followed by description of clear cell papillary renal cell carcinoma in 2006. Discussions about possible relationship of both tumors were published since their description. The main differential diagnostic feature was considered presence/absence of fibroleiomyomatous stroma-relationship of renal angiomyoadenomatous tumor in stroma-rich tumors. However, it was shown that stroma is reactive and nonneoplastic by its nature and that all other histologic, immunohistochemical, and molecular-genetic features of both entities are identical. In upcoming World Health Organization classification of renal tumors (2016), both lesions are considered as a single entity (clear cell papillary renal cell carcinoma [CCPRCC]). Most published cases followed the benign/indolent clinical course. In addition, most tumors has normal status of VHL gene (methylation, LOH 3p, mutations); however, CCPRCC was referred in patients with VHL syndrome. Another issue covered by this review is possible relationship of CCPRCC and "renal cell carcinoma with leiomyomatous stroma" (RCCLS). Renal cell carcinoma with leiomyomatous stroma shows clear cell cytology and abundant leiomyomatous stroma. Some of RCCLS are positive for cytokeratin 7; some are negative. Similar situation exists for relation of RCCLS and VHL gene abnormalities. It is so far unclear whether any relation between CCPRCC and RCCLS exists. From all published studies, it seems that these tumors are less likely related to each other.

Perivascular epithelioid cell tumors (PEComas) are rarely found in the urinary tract. The clinicopathologic characteristics of 10 cases, retrospectively collected from 5 medical institutions in 3 different European countries, are presented in this study. Male/female ratio was 3:7 and the average age at diagnosis was 62.7 years. Nine cases were sporadic and 1 showed germline mutation of the TSC2 gene. Eight cases were located in the kidney, 1 in the left adrenal and 1 in the right ureter. All of the patients were alive and free of disease at the time of last contact (mean follow-up, 14.1 mo). Four cases displayed a conventional morphology and 6 showed a prominent sclerotic stroma. By immunohistochemistry, melanocytic markers were consistently expressed, especially HMB-45 (10 cases), MiTF (9 cases), and Melan-A (6 cases). Desmin was expressed in 6 cases ; 2 cases were positive for CD117 ; a single case showed TFE3 expression. pMAPK, mTOR, and pAKT demonstrated variable immunostaining with focal positivity in 7, 4, and 2 cases, respectively. Cytokeratins were repeatedly negative in all cases. PEComas in the urinary tract, especially in the renal region, may show a relatively high frequency of the sclerosing histologic subtype. Knowledge of the distinct histology and immunohistochemical profile is vital to correctly diagnose this rare entity.

Rhabdoid morphology in renal cell carcinoma (RCC) may, like sarcomatoid change, be perceived as a type of dedifferentiation, and is a poor prognostic factor. Histologically, rhabdoid neoplastic cells are round to polygonal cells with globular eosinophilic cytoplasmic inclusions and eccentric vesicular nuclei and enlarged nucleoli. All types of RCC, including clear cell, papillary, chromophobe, collecting duct carcinoma, renal medullary carcinoma, acquired cystic disease-associated RCC, ALK-positive renal cancer and unclassified RCC, may display a variably prominent rhabdoid phenotype. Immunohistochemically, the cytoplasm of rhabdoid cells shows positivity for vimentin and/or cytokeratin. Ultrastructurally, cytoplasmic whorls/aggregates of intermediate filaments correspond to light microscopically observed inclusions. Genetically, a previous report suggests that combined loss of BAP1 and PBRM1 may be associated with rhabdoid morphology. As with sarcomatoid change, pathologists should describe, estimate and state the proportion of tumor cells with a rhabdoid phenotype in the routine pathology report of RCC.

Chromophobe renal cell carcinoma (CRCC) with neuroendocrine differentiation (CRCCND) has only recently been described. Eighteen cases of CRCC with morphologic features suggestive of neuroendocrine differentiation were selected from among 624 CRCCs in our registry. The tissues were fixed in neutral formalin, embedded in paraffin, cut into 4- to 5-μm-thick sections, and stained with hematoxylin and eosin. As CRCC with neuroendocrine features, tumors with following morphology were suggested: (1) trabecular/palisading/ribbon-like, gyriform, insular, glandular, and solid pattern ; (2) uniform polygonal cells formed in small islets ; and (3) cribriform pattern in combination with palisading. Selected cases were further analyzed using immunohistochemistry, electron microscopy, array comparative genomic hybridization, and fluorescence in situ hybridization. Cases were classified as CRCCND or CRCC with neuroendocrine- like features (CRCCND-L) based on the immunohistochemical expression of neuroendocrine markers: CRCCND, 4 cases, age range 49 to 79 years, size ranged from 2.2 to 22 cm, and CRCCND- L, 14 cases, age range 34 to 74 years, size range 3.8 to 16.5 cm. Follow-up information was available for 11 of 18 patients aged 0.5 to 12 years. Two of 4 CRCCNDs showed aggressive clinical course with metastatic spreading. Chromophobe renal cell carcinomas with neuroendocrine differentiation were focally positive for CD56 (4/4), synaptophysin (4/4), chromogranin A (1/4), and neuron-specific enolase (3/4). All 14 CRCCND- Ls were mostly negative or very weakly focally positive for some of the aforementioned markers. All 18 tumors were positive for cytokeratin 7 and CD117. Ultrastructural analysis showed poorly preserved neuroendocrine granules only in 2 of 4 analyzed CRCCNDs. Losses of chromosomes 1, 2, 6, and 10 were found in all analyzable CRCCNDs, whereas multiple losses (chromosomes 1, 2, 6, 10, 13, 17, and 21) and gains (chromosomes 4, 11, 12, 14, 15, 16, 19, and 20) were found in CRCCND-L.

Diffusion-weighted imaging (DWI) allows for differentiation of benign from malignant tumors, histological tumor types and their grade. The aim of the study was to evaluate the capabilities of DWI using 3 Tesla Magnetic resonance imaging (3T MRI) in the preoperative assessment of renal tumors.This retrospective study included 143 tumors in 139 patients (130 malignant tumors and 13 benign tumors) that were examined using DWI with b values of 50, 400 and 800 s/mm(2). In all tumors, the lowest value of apparent diffusion coefficient (ADC) in the solid tissue was measured and correlated with the histological finding.A significant difference between ADCs of malignant and benign tumors was found (p0.001). Comparison of the most common malignant and benign tumors clear-cell renal carcinoma (CCRCC) grade I and oncocytoma resulted in a difference of borderline significance with a marked overlap (p=0.046). By assessing the histological types of malignant tumors, we detected a significant difference between CCRCC and all other histological types (p=0.048 for chromophobe (CH) RCC, p=0.002 for papillary (P) RCC and p=0.002 for urothelial carcinoma (UC)). Mutual differentiation of other types of carcinomas was not feasible (p=1.0 in all cases). The differences between low-grade (grade I+II) and high-grade (grade III+IV) CCRCC was significant (p0.001). A significant difference was found even between CCRCC grade I and others (p=0.01 for grade II, p0.001 for grade III+IV, respectively).DWI may contribute in distinguishing CCRCC from other histological types and to determinits grade. The method has certain potential for distinguishing benign from malignant tumors; however, differentiation of the most frequently represented types, CCRCC grade I and oncocytoma, remains difficult.

To evaluate the proliferation activity in gliomas using 18F-fluorothymidine (18F-FLT)-positron emission tomography/computed tomography (PET/CT).Samples of 26 tumors were analyzed (mean age=51.6; range=26-72 years; 16 males, 10 females). All examinations were performed using a PET/CT scanner equipped with lutetium oxyorthosilicate (LSO) detectors. All data were acquired with a delay of 15 min, following intravenous application of 18F-FLT (dosed 2 MBq/kg of body weight). The PET/CT contained CT after intravenous application of iodinated contrast agent and high-resolution brain PET acquired during 15 min in one position. PET/CT was performed before confirmation of the histological diagnosis and the level of 18F-FLT accumulation was compared to the grading of the tumor evaluated using immunohistochemistry staining of Ki-67. Samples were obtained by stereotactic biopsy (5×) or surgical resection (21×).Five tumors of grade IV, 7 tumors of grade III and 14 tumors of grade II were found. Pre-bioptical discrimination between high-grade and low-grade tumors reached accuracy 92.3% (24/26), sensitivity 92.3% (12/13) and specificity 92.9 (13/14). The mean maximum standardized uptake value (SUVmax) in high-grade tumors was 2.23, significantly different from low-grade tumors (mean SUVmax 0.61, T=7.803, p0.0001).18F-FLT-PET/CT enables to estimate the proliferation activity of glioma before biopsy.

We report 5 cases of micropapillary urothelial carcinoma (MPUC) involving the renal pelvis (2), renal pelvis and ureter (2), and proximal ureter (1). The patients were 2 women and 3 men, ages 65 to 92 years (mean, 76.0 years). All tumors showed a high-grade transitional cell carcinoma component, and in 3 cases, there also were areas of in situ carcinoma. The case involving only the ureter occurred in a 65-year-old man with a history of nephrectomy 12 years previously for urothelial carcinoma of the renal pelvis. The tumor recurred in the ureteral stump. In all cases, areas displaying micropapillary architecture were observed. In 2 cases the micropapillary areas were noninvasive; in 1 case a pure invasive pattern was seen; and in 2 cases a mixed invasive and noninvasive pattern was present. the micropapillary pattern was invasive; and the case involving the ureteral stump contained invasive and noninvasive micropapillary carcinoma. All patients died of their tumors from 3 to 24 months after initial diagnosis. MPUC involving the renal pelvis and ureter is associated closely with advanced stages of disease and has highly aggressive behavior. Recognition of this growth pattern is important for prognosis and avoiding misdiagnosis with papillary renal cell carcinoma and other tumors.

Supplemental Digital Content is available in the text., Succinate dehydrogenase (SDH)-deficient renal carcinoma has been accepted as a provisional entity in the 2013 International Society of Urological Pathology Vancouver Classification. To further define its morphologic and clinical features, we studied a multi-institutional cohort of 36 SDH-deficient renal carcinomas from 27 patients, including 21 previously unreported cases. We estimate that 0.05% to 0.2% of all renal carcinomas are SDH deficient. Mean patient age at presentation was 37 years (range, 14 to 76 y), with a slight male predominance (M:F=1.7:1). Bilateral tumors were observed in 26% of patients. Thirty-four (94%) tumors demonstrated the previously reported morphology at least focally, which included: solid or focally cystic growth, uniform cytology with eosinophilic flocculent cytoplasm, intracytoplasmic vacuolations and inclusions, and round to oval low-grade nuclei. All 17 patients who underwent genetic testing for mutation in the SDH subunits demonstrated germline mutations (16 in SDHB and 1 in SDHC). Nine of 27 (33%) patients developed metastatic disease, 2 of them after prolonged follow-up (5.5 and 30 y). Seven of 10 patients (70%) with high-grade nuclei metastasized as did all 4 patients with coagulative necrosis. Two of 17 (12%) patients with low-grade nuclei metastasized, and both had unbiopsied contralateral tumors, which may have been the origin of the metastatic disease. In conclusion, SDH-deficient renal carcinoma is a rare and unique type of renal carcinoma, exhibiting stereotypical morphologic features in the great majority of cases and showing a strong relationship with SDH germline mutation. Although this tumor may undergo dedifferentiation and metastasize, sometimes after a prolonged delay, metastatic disease is rare in the absence of high-grade nuclear atypia or coagulative necrosis.

This study characterizes the clinicopathological spectrum of lymphoproliferations involving the breast nipple and/or areola. Morphologic, immunohistochemical, molecular-genetic, and clinical features of 58 specimens from 56 patients were analyzed. They were re-diagnosed as cutaneous lymphoid hyperplasia (CLH, n = 44); other benign lymphoid infiltrates (OBLI, n = 8); peripheral T-cell lymphoma, not otherwise specified (n = 1); cases with overlapping features of CLH and B-cell lymphoma (n = 3), one of them composed of spindle cells. Cutaneous lymphoid hyperplasia infiltrates were dense, composed mainly of B cells forming follicles with germinal centers (GC). Cutaneous lymphoid hyperplasia frequently showed features suggesting a malignancy as coalescing follicles with non-polarized germinal centers lacking mantle zones, and smudged infiltrates of lymphoid cells spreading into collagen (often as "Indian files"), smooth muscle, vessel walls, and nerve sheaths. Only two cutaneous lymphoid hyperplasias recurred; otherwise all patients are without disease (mean follow-up 62 months). Monoclonal rearrangement of immunoglobulin heavy chain gene was detected in five, and of T-cell receptor gamma gene in two cutaneous lymphoid hyperplasias using polymerase chain reaction (PCR), but the patients fared well too. In 47% of cases Borrelia burgdorferi was detected by polymerase chain reaction and/or serology, of which one was monoclonal. We conclude that cutaneous lymphoid hyperplasia is the most common lymphoproliferation of the breast nipple, rarely recognized clinically, and often overdiagnosed histologically as lymphoma.

We present, in a 47-year-old man, the first case of the signet-ring stromal tumor of the testis. The tumor was located beneath the tunica albuginea surrounded by the testicular tubules and rete testis. It was sharply circumscribed by a thin and irregular fibrous capsule. Histologically, it was composed of cells with a widespread signet-ring cell change separated by fibrous stroma. In some places, the signet-ring cells formed vague Indian files, thus resembling metastatic carcinomas with signet-ring cell morphology. Under high magnification, most of the cytoplasm of the tumor cells was seen to be replaced by an empty clear vacuole which pushed the nuclei to the periphery of the cells. Some of the nuclei were indented by the cytoplasmic vacuoles, others were without indentation. Only in a small area did the tumor show cells without a signet-ring cell change. They looked like epithelioid fibroblasts forming abortive and vaguely tubular structures. Mitoses and necroses were absent. Mucicarmine and PAS stains were negative. Immunohistochemically, the tumor was vimentin positive and it was negative with antibodies to cytokeratins, inhibin, prostatic acid phosphatase, prostate-specific antigen, smooth muscle actin, S-100 protein, EMA and calretinin. The signet-ring stromal tumor of the testis is thus similar morphologically and immunohistochemically to the signet-ring stromal tumor of the ovary. The patient was free of recurrence and metastasis 3 years after the excision.

We report a case of reactive syringofibroadenomatous hyperplasia in peristomal skin. The patient was a 62-year-old woman who had undergone abdominoperineal resection of the rectum for rectal adenocarcinoma with subsequent colostomy 2 years earlier. Clinically, a nodule and small, whitish, warty lesions developed at the outer margin of the stoma extending onto the adjacent skin. Following a clinical suspicion of adenocarcinoma, recurrent at the colostomy site, a 5 x 4 x 3-cm excision of the peristomal skin and the affected portion of the stoma was performed and submitted for histologic examination. The biopsy revealed a peculiar composite lesion of reactive syringofibroadenomatous hyperplasia and the excised part of the stoma. Several unusual histopathological features were detected in the syringofibroadenomatous part of the lesion such as the formation of plentiful hybrid epidermal-colonic mucosa glandular structures, intraepidermal areas of sebaceous differentiation, koilocytic changes, induction of rudimentary hair follicles, and intradermal mucinous lakes. The cellular composition of the glandular structures was mainly similar to that seen in a normal colonic mucosa epithelium. They also contained occasional Paneth cells. Being located at a distance from the stoma, these accentuated colonic mucosa epithelial glands reaching the epidermis may be a diagnostic pitfall prompting the consideration of adenocarcinoma involving the stoma. The rudimentary follicles and sebaceous differentiation were probably induced by an altered stroma and/or human papillomavirus (HPV): HPV, type 36 was identified by PCR using consensus primers followed by sequencing of the PCR products.

A unique and never-before-published example of clear cell renal cell carcinoma (CRCC) found among 9000 primary renal cell tumors is presented. The tumor contained such a dense concentration of glassy hyaline globules (GHG) in the cytoplasm of the neoplastic cells that it overshadowed the morphology of the neoplasm. The resulting appearance of the tumor was quite misleading and different from the conventional CRCC. The GHG were 7-30 microm in diameter. They were glassy and pale to slightly eosinophilic in color in hematoxylin-eosin. The GHG stained positively with periodic acid-Schiff and negatively with silver and Hale's colloidal iron. Immunohistochemically, they were also negative for anti Mycobacterium bovis antigen. At the ultrastructural level, the GHG were formed by an amorphous mass of stellate shape. The GHG were localized within rough endoplasmic reticulum. Molecular genetically, mutation of the distal part of exon 3 of the VHL gene causing elongation of the VHL protein was found in the tumor, thus confirming the diagnosis of CRCC.

Adenomatoid tumor (AT) is a benign, relatively rare neoplasm occurring primarily in the genital tract of both genders. Histologically, ATs were composed of fibrous tissue, which are separated by numerous slit-like and pseudotubular spaces. Peculiar "thread-like bridging strands" (TBS) crossing the pseudotubular spaces are typical morphologic feature. In this study, the frequency of occurrence of these TBS within a large series of ATs in various organs was examined. Sixty-nine cases were included in our study. Twenty-eight cases occurred in women, 41 cases in men. Tumors were located in the myometrium, fallopian tube, ovary, epididymis, tunica albuginea, and testicular parenchyma. Tumor size ranged from 0.8 to 8.2 cm (mean, 2.7 cm). TBS were found in 100% of cases. Presence of thin intraluminal TBS within ATs was a constant morphologic feature independently on gender and localization of the lesions. Ultrastructurally, they were always formed by apposition of attenuated cytoplasm of two adjacent mesothelial cells. In our opinion, TBS are morphologically very specific for ATs and we are not aware of any other epithelial structure in any organ demonstrating as appearance similar to these TBS of ATs.

We present the case of a 74-year-old Caucasian male with an expansive process of the left kidney. No clinical and laboratory signs of polycytemia or hypertension were present. Microscopically, the spherical main tumor mass was composed of small basophilic cells arranged in longitudinal branching tubules typical of metanephric adenoma (MA). Another component, different from MA, was formed by a tumor in a papillary and tubopapillary arrangement. This component was diagnostic of grade 3 papillary renal cell carcinoma. The third component, which was merging with the papillary one, was composed of sarcomatoid, spindle cell carcinoma with prominent nuclear polymorphism and a high number of mitotic figures, including atypical mitoses. The sarcomatoid component filled the entire cortico-medullary space and infiltrated the surrounding non-neoplastic renal tissue, including the renal pelvis. Areas of necroses, hemorrhages, and mitotic figures were frequent. No structures of Wilm's tumor were seen in our case. One year after the excision, the patient is without recurrence and metastasis. The existence of the above mentioned tumor supports the hypothesis that metanephric adenomas and papillary renal cell carcinomas are interrelated lesions.

Mixed epithelial and stromal tumor of the kidney is a rare benign tumor that consists of both epithelial and stromal cells. To date, eight malignant cases have previously been reported in female patients only. We report the first case of malignant mixed epithelial and stromal tumor of the kidney in a male patient. A 67-year-old Japanese man receiving hormonal therapy for prostatic cancer was found to have a right renal cystic tumor and underwent right nephrectomy. Histologically, the tumor was composed of benign epithelial and stromal cells in addition to malignant undifferentiated stromal cells. Immunohistochemically, the malignant stromal component was positive for cluster of differentiation 99 and B-cell lymphoma 2, but no chimeric transcripts for synovial sarcoma were identified. Finally, a diagnosis of malignant mixed epithelial and stromal tumor of the kidney was recorded. Urologists and pathologists should recognize that malignant mixed epithelial and stromal tumors of the kidney might occur in male patients receiving hormonal therapy for prostatic cancer.

We describe 5 cases of urothelial carcinoma (UC) of the renal pelvis, which grew in a distinctive gross and microscopical pattern into the renal parenchyma. Five patients (2 men and 3 women, mean age 67.4 years) underwent nephrectomy for vague clin ical findings. The cut surface of the tumor was white to light gray and the consistency was elastic. The corticomedullary border was indistinct, resulting in an appearance that suggested amyloidosis or myeloma. The renal pelvis showed normal mucosa with areas of dysplastic changes. The tumors spread from the renal pelvis in a diffuse and irregular, infiltrative pattern and surrounded intact glomeruli. Detailed sampling of invasive tumor component showed foci of UC with transitions to clear squamous cells. The predominant clear squamous neoplastic cells had foci of granular eosinophilic cytoplasm and resembled conventional renal cell carcinoma. Four pa tients were alive and without signs of the disease for 5 months to 4 years after nephrectomy; 1 died of generalized tumor 7 months after nephrectomy. The unusual gross and microscopic features result in varied problems in differential diagnosis, which are discussed herein. Int J Surg Pathol 10(1):41-45, 2002

Birt–Hogg–Dube syndrome is a familial genodermatosis, of which patients frequently develop renal neoplasms, fibrofolliculomas and pneumatocele. Here, we report a mother and daughter with renal neoplasms surgically resected (69 and 46 years-of-age at surgery, respectively). The mother's tumor was diagnosed as an unclassified type renal cell carcinoma associated with microscopic tumorous nodules, whereas the daughter's tumor was a hybrid oncocytic/chromophobe tumor. The germline mutation analysis of the responsible gene, FCLN (the folliculin gene), showed a deletion of 18 bp in exon 5 (c.332_349del/p.H111_Q116del), predicting an alteration of the amino acid sequence of “HPSHPQ” replaced by a single amino acid, “L”. This is a novel germline mutation of the FCLN gene that has not been previously reported.

The disease concept of clear cell (tubulo) papillary renal cell carcinoma (CCP-RCC) as a distinct subtype of renal cell carcinoma has been recently established. First described in the setting of end stage renal disease, this tumor type is more frequently recognized and encountered in a sporadic setting. In this article, we provide an overview of the recent understanding of this tumor. Macroscopically, tumors are well circumscribed with well-developed tumor capsule. Histologically, the tumor cells are cuboidal to low columnar cell with clear cytoplasm and papillary and tubulo-papillary configuration. Immunohistochemically, tumor cells generally show diffuse expression for cytokeratin 7, CA9 (cup-shaped pattern), HIF-1, GLUT-1 and high molecular weight cytokeratin, but negative for AMACR, RCC Ma and TFE3. CD10 is negative or focally positive in most tumors. Genetically, this tumor has no characteristics of clear cell RCC or papillary RCC. Prognostically, patients with CCP-RCC behave in an indolent fashion in all previously reported cases. In conclusion, although this tumor has been integrated into recent International Society of Urologic Pathology Classification of renal neoplasia, both aspects of disease concept and clinical behavior are yet to be fully elucidated. Further publications of large cohorts of patients will truly help understand the biologic potential and the molecular underpinnings of this tumor type.

Xp11.2-translocation renal carcinoma (TRCC) is suspected when a renal carcinoma occurs in young patients, patients with a prior history of exposure to chemotherapy and when the neoplasm has morphological features suggestive of that entity. We retrieved 20 renal tumours (from 17,500 archival cases) of which morphology arose suspicion for TRCC. In nine cases, TFE3 translocation was confirmed by fluorescence in situ hybridisation analysis. In 9 of the remaining 11 TRCC-like cases (7 male, 4 female, aged 22-84 years), material was available for further study. The morphological spectrum was diverse. Six tumours showed a mixture of cells with eosinophilic or clear cytoplasm in tubular, acinar and papillary architecture. One case was high grade with epithelioid, spindle cell and sarcomatoid areas. Another showed tubular, solid, and papillary areas and foci containing spindle cells reminiscent of mucinous tubular and spindle cell carcinoma. The third showed dyscohesive nests of large epithelioid and histiocytoid cells in a background of dense lymphoplasmacytic infiltrate. By immunohistochemistry, keratin AE1/AE3 was diffusely positive in three tumours, while CK7 strongly stained one tumour and another focally and weakly. CD10 and Pax8 were expressed by eight, AMACR and vimentin by seven, CA-IX by four and TFE3 and cathepsin K by two tumours. Of the two TFE3-positive tumours, one showed polysomy of chromosome 7 and the other of 17; they were VHL normal and diagnosed as unclassifiable RCC. Of the seven TFE3-negative tumours, three showed polysomy of 7/17 and VHL abnormality and were diagnosed as combined clear cell RCC/papillary RCC. One TFE3-negative tumour with normal 7/17 but LOH 3p (VHL abnormality) was diagnosed as clear cell RCC. One TFE3-negative tumour with polysomy 7/17 but normal VHL was diagnosed as papillary RCC, and two with normal chromosomes 7/17 and VHL gene were considered unclassifiable. As morphological features and IHC are heterogeneous, TRCC-like renal tumours can only be sub-classified accurately by multi-parameter molecular-genetic analysis.

Birt-Hogg-Dube syndrome (BHDS) is an autosomal dominant inherited disorder characterized by clinical features of skin lesions, pulmonary lesions and renal tumor. The gene responsible for this syndrome is located on chromosome 17p11.2 and designated as FLCN. In this article, we review renal tumors associated with BHDS with a focus on clinical and pathobiological aspects. Renal tumors often occur multifocally or bilaterally in the imaging analyses or gross examination. Histological examination of renal tumors includes a variety of subtypes such as hybrid oncocytic tumor, chromophobe renal cell carcinoma (RCC), oncocytoma, clear cell RCC and papillary RCC. The histologic discordance in multiple tumors seems to be characteristic of this syndrome. Oncocytosis is observed histologically in about half of the cases. Several investigations have elucidated that folliculin may be involved in the mammalian target of rapamycin (mTOR) pathway recently. Renal tumors composed of clear cells may behave in an aggressive fashion. However, renal tumors including hybrid oncocytic tumor, chromophobe RCC and oncocytoma behave mostly in an indolent fashion.

In this article, we searched for the common histologic characteristic of renal tumors in patients with Birt-Hogg-Dube syndrome (BHDS). We selected 6 patients with histologically confirmed renal tumor in BHDS. Germline FLCN gene mutation has been identified in 5 patients. Multifocality and bilaterality of the renal tumors were pathologically or radiologically confirmed in 5 and 2 cases, respectively. Histologic subtypes of the dominant tumor included 3 previously described hybrid oncocytic tumors, one composite chromophobe/papillary/clear cell renal cell carcinoma (RCC) and one unclassified RCC resembling hybrid chromophobe/clear cell RCC. In one case, chromophobe RCC and clear cell RCC were separately observed. Small papillary lesions located in the peripheral area of the tumor, which we designated as intratumoral peripheral small papillary tufts, were identified in all patients. In conclusion, multifocality/bilaterality of renal tumors, discordance of histologic subtypes, and the presence of intratumoral peripheral small papillary tufts may be important clues to identify BHDS-associated renal tumors.