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Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare subtype of RCC classified as a molecularly defined RCC in the fifth edition of the WHO. Most gene alterations in patients with SDH-deficient RCC involve the SDHB subunit, with less involvement of the SDHC, SDHA, and SDHD subunits. Four cases of SDHA-deficient RCC have been reported in the literature, of which one case was associated with an NF2 gene mutation. Herein, we report six novel SDHA-deficient RCC cases, including two cases with NF2 gene mutations. In contrast to the typical morphology of SDH-deficient RCC, the six tumors mainly displayed glandular, sheet-like, or papillary growth patterns with prominent nucleoli (Grades 2-3), among which two cases with NF2 mutations had prominent nucleoli (Grade 3), large transparent vacuoles in the cytoplasm, and a large number of lymphocytes in the stroma. Six tumors showed negative immunohistochemical staining for SDHA and SDHB, and three cases presented with high expression of PD-L1. Second-generation sequencing revealed novel pathogenic somatic SDHA gene mutation and NF2 gene mutations in six and two tumors, respectively. Follow-up data were collected for the six patients with a follow-up time ranging from 7 to 268 months, and all six patients have survived to date. One patient received targeted therapy for tumor metastasis to the lungs after seven months, and another patient with an NF2 gene mutation received immunotherapy for lymph node metastasis revealed during surgery. SDHA-deficient RCCs with NF2 gene mutations have the ability to metastasize but might respond well to immunotherapy. For the first time, we report the largest number of SDHA-deficient RCC cases and comprehensively investigate their clinicopathological and molecular features to provide important guidance for diagnosis and clinical immunotherapy., Competing Interests: Declaration of Competing Interest All authors declare that we have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Biphasic hyalinizing psammomatous renal cell carcinoma (BHP RCC) with NF2 gene mutations is a newly described provisional category of renal cell carcinoma (RCC). Here we described three additional cases of BHP RCC with CYP2A6 gene mutation besides NF2 gene. The carcinomas were predominantly unencapsulated, and two of them had a rounded, nodular interface with the native kidney while one had perirenal adipose tissue invasion. Histopathologically, all neoplasms had a characteristic biphasic appearance of smaller cells clustering around basement membrane material within larger acini, forming pseudorosettes or a glomeruloid pattern. The smaller cells were focally spindle-shaped in two carcinomas. Psammoma bodies were shown in two carcinomas. Cellular necrosis and perineural invasion was identified in one case. Immunohistochemically, Vimentin, EMA, P504s were extensively expressed while RCC and CD10 were only expressed in larger cells. CK7 was positive in one tumor. CYP2A6 gene mutation (CYP2A6 NM_000762.6: exon4:c.A580G:p.K194E) was revealed in three tumors by Whole-genome exome sequencing, which was further confirmed by Sanger sequencing. Only one case harbored a somatic termination mutation in NF2 gene. NF2 promoter methylation was observed in the other two cases. Clinically, one patient died of disease with widespread bone metastases confirmed by biopsy at the ninth month after surgery but the other two patients had no evidence of recurrence or metastases (follow-up period 9-90 months). Our findings validated previously described clinicopathological features and NF2 gene mutation or promoter methylation of BHP RCC. In addition, we reported different IHC pattern of BHP RCC and further revealed the recurrent CYP2A6 genetic alteration., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Biphasic squamoid alveolar papillary renal cell carcinoma (BSARCC) is a recently described renal tumor, considered as a unique rare morphological pattern of PRCC in the 2022 WHO classification. We aimed to further explore the clinicopathological, immunophenotypic, and molecular genetic characteristics of BSARCC in a Chinese cohort. The clinicopathological data of 8 patients with BSARCC were collected for morphology observation and immunohistochemical staining. QRT-PCR was performed to detect BRAF gene mutation. The abnormalities of chromosomes 7, 17 and Y, and CCND1 gene were investigated by fluorescence in situ hybridization (FISH). Among the 8 cases, 5 were males and 3 were females. 6 cases were revealed by physical examination incidentally, and 2 cases were presented with low back pain and hematuria. Microscopically, the tumors were mainly composed of small cells with different proportions of large cells. The small cells were arranged in acinar, compact and long narrow tubular, solid sheet or papillary structures. Single or clustered large cells were arranged in glomerular structures in the acinar cavity formed by small cells. Among the 8 cases, 2 cases had a small amount of typical type I papillary renal cell carcinoma without large cells at the edge of the tumor. And 5 cases presented the swallowing phenomenon of lymphocytes or neutrophils in the cytoplasm of a few large cells. Immunohistochemical staining showed both large and small cells were diffusely and strongly positive for CK7, P504s, EMA, and vimentin. MET was expressed in most tumors (6/8), and large cells (70-90%) exhibited a prominent higher positive rate than small cells (20-90%). CD57 was positive in both large and small cells in 5 cases. Notably, CyclinD1 was exclusively expressed in large cells, while RCC marker was mainly expressed in small cells. Large cells showed a higher ki67 index than small cells. BRAF V600E mutation was negative in all cases. FISH showed 4 cases had chromosome 7 trisomy, 2 cases had chromosome 17 trisomy, and 4 of 5 male patients had Y chromosome deletion. CCND1 gene amplification or rearrangement was not revealed in any case. Follow-up data were available in 8 cases ranging from 3 to 66 months, and there was no recurrence or metastasis of the tumor. BSARCC is a rare unique morphological pattern of papillary renal cell carcinoma, featured by the presence of two cell populations of different morphology and immunophenotype. Distinctive CyclinD1 and RCC immunostainings are essential in diagnosing this type of renal tumor. Large and small cells may be tumor cells in different stages of proliferation and differentiation, and large cells immunoreactive to CyclinD1 and presenting higher ki67 index might be more aggressive than small cells. The anomalous expression of CyclinD1 in large cells is not due to the aberrance of CCND1 gene itself. Most BSARCC is low-stage and inert with a favorable prognosis. Our study not only validates previously described clinicopathological features, but also supplements the clinicopathological features and expands the potential genetic alterations and available clinical outcome data of BSARCC., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier GmbH.)

Aims: This study retrospectively investigated the morphological, immunohistochemical and molecular genetic features of papillary renal neoplasm with reverse polarity (PRNRP), a recently described renal tumor., Methods and Results: Eleven cases of PRNRP were collected, and 16 cases of type I and 9 cases of type II papillary renal cell carcinoma were included as a control series. Pathological features were evaluated based on HE staining and immunohistochemistry. KRAS exon 2 and BRAF V600E mutations were detected by Real-time PCR and Sanger sequencing. Fluorescence in situ hybridization was conducted for identification of chromosomal abnormalities. Hemosiderin deposition was found in a small amount of tumor cells in 6 cases. Multifocal or patchy necrosis (5/11), small focal invasion of the pseudocapsules or renal parenchyma (6/11), and breakthrough of renal capsule with nerve invasion (1/11) were revealed, inconsistent with the previous view that the tumor lacks necrosis and intercellular hemosiderin. Immunohistochemical staining (diffusely positive for CK7 and GATA3, negative for CD117 and vimentin, and negative to weakly positive for P504S) and high frequency of KRAS mutations in exon 2 (9/10) supported the identification and inclusion of our cases. Chromosome 7 trisomy (1/7), chromosome 17 trisomy (0/7) and chromosome Y deletion (0/5 male patients) were seldom detected in this tumor. All patients were alive without metastasis or recurrence at the end of the follow-up., Conclusion: Our findings may highlight the possibility of a low malignant potential of this emerging entity. We suggest that the tumor be classified as a novel renal cell tumor subtype independent of papillary renal cell carcinoma., (© 2022. The Author(s).)

Objective: This study aimed to investigate the clinicopathological and molecular characteristics of ELOC(TCEB1)-mutant renal cell carcinoma., Methods: Sanger sequencing was used to assess 32 cases originally diagnosed as clear cell renal cell carcinoma with CK7 positive and/or fibromyomatous stroma. Of these, 4 patients with ELOC(TCEB1) gene mutation were screened, and their clinicopathological data were collected for histomorphological observation, immunohistochemical staining, and follow-up, and relevant pieces of literature were reviewed., Results: The 4 patients with ELOC(TCEB1) mutations were all males and aged between 57 and 64 years (median age: 59 years old). The tumor was located in the renal cortex, with a diameter of 2-3.5 cm. The cross-section was grayish-yellow and grayish brown, solid and nodular, and clearly demarcated from the surrounding tissues. Of the 4 patients, 3 harbored a thick fibrous pseudocapsule rich in smooth muscle and were separated from the surrounding normal renal tissue, and 2 of them showed focal invasion into the pseudocapsule, whereas 1 patient had no capsule but had focal invasion into the surrounding renal parenchyma. The tumor tissues mainly exhibited elongated or branched aciniform or tubular structures, commonly accompanied by interspersed small cystic and focal clustered short papillary structures. The cytoplasm of the tumor cells was rich and lightly stained, and the nuclear grading ranged from 1 to 2. All patients showed loose edema in the stroma, and 2 patients showed a small number of interspersed smooth muscle bundles. All 4 patients showed EMA, CA9, AMACR, and TCEB1 expression, and TCEB1 was mainly located in the nucleus. Vimentin, CK7, and CD10 expressions were observed in most cases; CD117, TFE3, HMB45, and melanA were not expressed in all tumors; the expression rate of Ki67 was 3%- 8%. All 4 patients had a point mutation in ELOC(TCEB1) Y79C. The patients were followed up for 24-93 months (mean 49 months), and all of them survived to date without recurrence or metastasis., Conclusion: ELOC(TCEB1)-mutant renal cell carcinoma is a rare type of renal cell carcinoma, which tends to occur in middle-aged and elderly men. The main characteristics of this tumor are the branching alveolar or tubular structure with clustered short papillae, presence of fibromyomatous stroma, and the expression of CK7, CA9, CD10, and AMACR. Positive TCEB1 nuclear staining may be an important marker and the Sanger sequencing method is helpful for the diagnosis of this type of RCC. Most patients harbor tumors exhibiting low nuclear grade and inert clinical behavior, and a few tumors exhibit high nuclear grade and aggressive characteristics., (Copyright © 2022 Elsevier GmbH. All rights reserved.)

Clear cell renal cell carcinoma (CCRCC) with sarcomatoid differentiation (CCRCCS) displays invasive behavior, poor prognosis, and poor therapeutic response. The present study was aimed to gain new insights into the molecular mechanisms of sarcomatoid transformation, and identify new prognostic and therapeutic targets for CCRCCS. Whole exome sequencing was performed on matched carcinomatous and sarcomatoid elements from five specimens with CCRCCS. A non‑synonymous single‑nucleotide polymorphism (SNP) of cadherin 23 (CDH23) was further studied through Sanger sequencing in expanded 40 specimens with CCRCCS and 50 specimens with CCRCC. Carcinomatous and sarcomatoid elements shared most somatic single‑nucleotide variants (SSNVs) as revealed through whole exome sequencing. Sarcomatoid element had higher overall SSNVs than carcinomatous element. A highly frequent mutation of CDH23 (rs3802711) was observed in CCRCCS that resulted in an alteration in the highly conserved calcium‑binding site in the three‑dimensional (3D) structure mediating the functions of cadherins. In the expanded 90 specimens, CDH23 SNP (rs3802711) was a highly frequent mutation in CCRCCS than that in all CCRCC samples and even high grade CCRCC. Cox multivariate analysis indicated that CDH23 (rs3802711) genotype was an independent prognostic factor affecting the overall survival of the cohort. CDH23 gene and protein were negatively or weakly expressed in most CCRCCS specimens with CDH23 mutation. The present study revealed, for the first time, that the CDH23 (rs3802711) was a highly genetic risk factor for CCRCCS. It was associated with the decreased expression of CDH23 protein, resulting in the absence of cadherin function of CDH23, indicating that the CDH23 mutation may be involved in the sarcomatoid transformation in CCRCCS. Collectively, a novel and specific SNP of CDH23 was identified in CCRCCS and a new candidate cadherin involved in EMT was revealed. Furthermore, a new prognostic evaluation factor and potential therapeutic target for CCRCCS was identified.

Xp11.2 translocation/TFE3 rearrangement-associated renal cell carcinoma (RCC) and Xp11 translocation renal mesenchymal tumor are distinct tumor entity. To broaden the spectrum of Xp11 neoplasms, we investigated a novel tumor exhibiting morphologies overlapping Xp11.2 translocation/TFE3 rearrangement-associated RCC and the mesenchymal counterpart with melanocytic differentiation by immunohistochemistry, fluorescence in situ hybridization (FISH) and RNA sequencing, as well as literature review. Histologically, the tumor was composed of three different types of tumor cells, including a large proportion of clear cells, small round cells, and a few spindle cells, presenting a relatively clear border in the majority area. The nuclei of all tumor cells showed extensively and strong positive expressions of TFE3. Whereas, the clear cells positively expressed the RCC-related markers including PAX8, RCC marker and CD10, and negatively expressed HMB45; On the contrary, the small round cells and spindle cells positively expressed melanocytic marker HMB45, and negatively expressed PAX8, RCC marker and CD10. The ki67 index was higher in the small round cells and spindle cells than that in the clear cells. FISH revealed the rearrangement of TFE3 gene in all the three types of cells. The NONO-TFE3 fusion gene was detected in all tumor cells by RNA sequencing. This unique Xp11 translocation-associated neoplasm might represent a distinct entity overlapping Xp11 translocation RCC and the mesenchymal counterpart with melanocytic differentiation, broadening the spectrum of Xp11 neoplasms. The patient died of tumor recurrence and lung metastasis after seven months after the surgery suggesting those tumors have an unfavorable prognosis., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Aims: Anaplastic lymphoma kinase (ALK)-rearranged renal cell carcinoma (RCC) is a rare subtype of RCC reported in recent years, with eight cases so far. The aims of the present study were to screen ALK-rearranged cases from a large cohort of RCCs in China to determine the frequency of ALK rearrangement and investigate the clinicopathological features and outcomes., Methods and Results: Tissues from a total of 477 RCC patients in China were embedded into tissue microarrays for immunostaining. Fluorescence in-situ hybridization (FISH) and fluorescence quantitative reverse transcription polymerase chain reaction (RT-PCR) were applied to identify and confirm the rearrangement of ALK, and to identify the genes fused with ALK. ALK expression was identified in two of 477 RCCs. By FISH analysis, the two tumours showed either a 1R1G1F or a 2R2G signal pattern, indicating rearrangement involving ALK. Fluorescence quantitative RT-PCR detected the TPM3-ALK fusion and EML4-ALK fusion transcripts in the two tumours, respectively. Follow-up data were analyzed for the two cases and eight other ALK-rearranged RCCs reported in the literature. Two patients died from RCCs, on the 16th month and 48th month after surgery, respectively. The 5-year cancer-specific survival rate of patients with the 10 ALK-rearranged RCCs was lower than that of patients with International Society of Urological Pathology (ISUP) G1, G2 and G3 clear cell RCC (CCRCC) and papillary RCC (PRCC), but higher than that of patients with G4 CCRCC and PRCC., Conclusions: ALK-rearranged RCC is a rare subtype of adult RCC and is associated with distinct histological features and a poor prognosis. Identification of ALK-rearranged RCC has important clinical significance, because patients might benefit from ALK inhibitor therapy as used in lung adenocarcinoma., (© 2017 John Wiley & Sons Ltd.)

Background: Renal cell carcinoma (RCC) with sarcomatoid differentiation is a relatively rare tumor containing both carcinoma and sarcomatoid components. However, there has not been a systemic study on immunophenotypes of renal cell carcinoma with sarcomatoid differentiation, especially using some renal specific immunohistochemical markers. In this study, we aimed to comprehensively investigate the distinct immunophenotypes of RCC with sarcomatoid differentiation to analyze the pathogenesis of sarcomatoid differentiation and identify new prognostic factors in RCC with sarcomatoid differentiation., Methods: A total of 42 cases of RCCs with sarcomatoid differentiation were enrolled into the study. Immunohistochemistry study was performed on tissue microarrays to evaluate the expressions of 19 immunohistochemical markers including a series of epithelial, mesenchymal markers and RCC specific markers. Kaplan-Meier method was applied to assess the prognostic values of CD10, CAIX, p53 and Bcl-2., Results: Histologically, 42 cases of RCCs with sarcomatoid differentiation presented with different proportions of carcinoma and sarcomatoid components. The cohort contained 35 cases of clear cell renal cell carcinoma (CCRCC) and 7 cases of chromophobe renal cell carcinoma (ChRCC) based on the carcinoma components. Immunohistochemically, all cases were positive for vimentin, and 80% of cases showed immunostaining for at least one epithelial marker, such as CK, EMA, CK7 and CK18. Notably, the expression rates of CAIX, CD10 and PAX8 in sarcomatoid cells were 76%, 76% and 64%, respectively. The carcinoma component of the tumors showed differentient labeling for CAIX, CD10, vimentin, CK7 and CD117 in CCRCC vs ChRCC, but the sarcomatoid component lost the specificity for these markers ( p < 0.05). Patients with positive expressions of CAIX, p53 and Bcl-2 had a poor prognosis., Conclusions: The sarcomatoid cells in RCC with sarcomatoid differentiation express both epithelial and mesenchymal markers, supporting their epithelial origin. PAX8, CAIX and CD10 could be used as the reliable and useful markers to determine the renal origin of sarcomatoid cells such as in fine needle aspiration cases and metastatic RCC with sarcomatoid differentiation. CAIX, p53 and Bcl-2 might play important roles in the transformation from renal cell carcinoma to high malignant sarcomatoid differentiation, and these three immunohistochemical markers are adverse prognostic factors for the survival of patients with RCC with sarcomatoid differentiation.

A sort of PRCC with distinct eosinophilic cytoplasm named Oncocytic Papillary Renal Cell Carcinoma (OPRCC) has been increasingly attracting the attention of researchers recently. However, owing to the rarity of OPRCC, the clinicopathological and genetic features of the tumor have still not been well elucidated and whether it should be regarded as an independent subtype of PRCC remains controversial. Herein, a cohort of 14 OPRCCs was studied with the aim of revealing the distinct clinicopathological features, facilitating the classification and correct diagnosis of OPRCC. Men and women each accounted for a half of the cohort with the median age of 64 years old. The majority of patients (9/14) were identified by medical examination and the remaining presented with macroscopic haematuria or lumbar pain. Grossly, tumors were well demarcated and varied from 1.5 to 9cm in diameter. Microscopically, typical OPRCC possessed fine papillary structures with delicate fibrovascular cores, lined with a single layer cell with large, deeply eosinophilic granular cytoplasm and round or polygonal-shaped nucleus exhibiting low nuclear grade in 10 cases (WHO/ISUP grade I-II). Most cases (12/14) possessed hemosiderin-laden and foam-like cells. Focal necrosis presented in 5 cases. Furthermore, solid oncocytoma-like areas appeared in 5 cases and focal sarcomatoid differentiation was identified in 1 case. Immunohistochemically, the majority of tumors presented high expression rates of alpha-methylacylCoA racemase (AMACR), CD10 and vimentin, which were similar to type 2 PRCC. The immune markers including cytokeratin-7 (CK7), KSP-cadherin and EMA exhibited variable positive immunostaining. Genetically, FISH analysis demonstrated trisomy of chromosome 7 in 7 OPRCCs and trisomy of chromosome 17 in 6 OPRCCs. Among 7 male cases, loss of chromosome Y was revealed in 2 cases. Follow-up data was available in 13 patients and only 1 patient died of bone metastasis of the tumor. The other 12 patients were all alive uneventfully at a mean follow-up time of 37 months, indicating that OPRCC is a unique subtype of PRCC with indolent clinical behavior. In conclusion, OPRCCs show a single layer tumor cell of low nuclear grade similar to type 1 PRCC, and abundant eosinophilic cytoplasm resembling type 2 PRCC. Furthermore, the tumor presents the same immunophynotype as type 2 PRCC but the same genetic features and prognosis as type 1 PRCC. OPRCC should be classified as an independent subtype of PRCC with different features from both type 1 and type 2 PRCC., (Copyright © 2016 Elsevier GmbH. All rights reserved.)

Objective: To study the clinicopathological features and prognosis of renal cell carcinoma with sarcomatoid differentiation (RCCS)., Methods: The clinical data and pathological materials of 18 RCCS cases were retrospectively reviewed.The follow up data were available in 13 RCCS cases, and were compared with the follow up data of 20 cases of clear cell renal cell carcinoma (RCC)., Results: The 18 RCCS patients included 14 males and 4 females, and were 49-79 years old (mean age: 62 years old). On gross examination, the tumor size was 3-19 cm in diameter (mean diameter: 9.8 cm). Histologically, all tumors were composed of a mixture of typical RCC with sarcomatoid component, including 9 clear cell RCC, 3 chromophobe RCC and one papillary RCC. The sarcomatoid components included 9 cases of fibrosarcoma, 3 cases of leiomyosarcoma, 5 cases of malignant fibrous histocytoma and one case of undifferentiated sarcoma. Immunohistochemistry showed that the sarcomatoid components were strongly vimentin-positive in 18 cases, and one or more epithelial markers (EMA, AE1/AE3, CK7, CK18) were expressed to varying degrees in 14 cases, but the high-molecular weight keratin 34βE12 was scarcely expressed. The sarcomatoid components presented positive expressions of CAIX in 88.9% (16/18) and CD10 in 72.2% (13/18) cases. Among the 18 RCCS patients, 13 patients were followed-up: 9 patients died in 1-25 months after the surgery, of which 5 cases died of lung or bone metastasis, and 4 patients died of systemic failure. The twenty RCC cases without sarcomatoid differentiation were followed up for 3-65 months after the surgery, and the majority of them was alive uneventfully except for 2 cases who died of lung or bone metastasis of the tumor. The Kaplan-Meier survival analysis showed that the median survival time of the 18 RCCS patients was 8 months, while that of the 20 RCC cases without sarcomatoid differentiation was 62 months (P<0.001)., Conclusions: The presence of sarcomatoid differentiation in renal cell carcinoma indicates highly aggressive behavior and poor prognosis. The positive expressions of the immune markers CAIX and CD10 may play important roles in the transformation from renal cell carcinoma to sarcomatoid component.

Objective: To study the immunohistochemical expression of S100A1, GLUT-1 and Cavolin-1 and its diagnostic significance in renal tumors with oncocytic features., Methods: Tissue microarray and immunohistochemical staining for S100A1, GLUT-1 and Cavolin-1 were carried out in 59 cases of renal tumors with oncocytic features, including 19 cases of renal oncocytoma, 15 cases of clear cell renal cell carcinoma (CCRCC) with eosinophilic cells, 11 cases of eosinophilic variant of chromophobe renal cell carcinoma, 7 cases of oncocytic papillary renal cell carcinoma and 7 cases of epithelioid angiomyolipoma., Results: S100A1 was expressed in renal oncocytoma, with a positive propotion of 16/19 (including 14 cases showing widespread and strong positivity). On the other hand, the rate of expression of S100A1 was 2/11 in eosinophilic variant of chromophobe renal cell carcinoma, 10/15 in CCRCC with eosinophilic cells, 3/7 in oncocytic papillary renal cell carcinoma and 6/7 in epithelioid angiomyolipoma (P>0.05). The difference of S100A1 expression between renal oncocytoma and eosinophilic variant of chromophobe renal cell carcinoma was statistically significant. GLUT-1 was located in cell membrane, with a positive rate of 13/15 in CCRCC with eosinophilic cells, 7/19 in renal oncocytoma, 4/7 (weak) in oncocytic papillary renal cell carcinoma, 1/11 in eosinophilic variant of chromophobe renal cell carcinoma and 0/7 in epithelioid angiomyolipoma. The rate of expression of Cav-1 was 6/15 in CCRCC with eosinophilic cells, 2/7 in oncocytic papillary renal cell carcinoma, 5/7 in epithelioid angiomyolipoma, 2/11 (weak) in eosinophilic variant of chromophobe renal cell carcinoma and 0/19 in renal oncocytoma. S100A1 showed high sensitivity and 50% specificity in the diagnosis of renal oncocytoma. GLUT-1 and Cav-1 showed high specificity and sensitivity in the diagnosis of CCRCC and epithelioid angiomyolipoma., Conclusions: S100A1 is widely expressed in various oncocytic renal neoplasms and helpful in differential diagnosis of renal oncocytoma from eosinophilic variant of chromophobe renal cell carcinoma, but not from other 3 oncocytic renal tumors. Overexpression of GLUT-1 can be used in distinction between CCRCC and renal oncocytoma. Cav-1 is widely expressed in CCRCC and epithelioid angiomyolipoma but not in renal oncocytoma. Cav-1 expression thus rules out renal oncocytoma.

Objective: To investigate the clinicopathological characteristics and the diagnosis of multilocular cystic renal cell carcinoma (MCRCC)., Methods: The clinicopathological data of 19 MCRCC cases were collected and immunohistochemical staining assays were carried out. Forty-six cases of other cystic kidney lesions within the same period were collected as controls, including extensively cystic clear cell RCC (12 cases), clear cell tubulopapillary renal cell carcinoma (6 cases), tubulocystic carcinoma (2 cases), simple cortical cysts (22 cases), multilocular cystic nephroma (1 cases) and multicystic kidney (3 cases)., Results: The patients included 14 males and 5 females. The ages ranged from 31 to 66 years (median age = 50 years). Most of the MCRCC cases were detected incidentally in physical examination, occasionally accompanied with hematuria, back pain or other symptoms. The follow-up period of 17 patients ranged from 6 to 170 months. All patients were alive without evidence of tumor recurrence or metastasis. Pathological findings showed that macroscopically, tumor size ranges from 1.5 to 7.0 cm in the maximum diameter, generally a entirely of various sized. The cysts contain serous, hemorrhagic or turbid fluid. Solid areas or substantially discernible mural nodules were absent; histologicallly, single layer of cuboidal and flattened epithelial tumor cells were lined in the cysts, described as clear cytoplasm, small nuclear, no nucleoli and low Fuhrman nuclear grade (I or II). Multilayer tumor cells could be observed in a few cysts, with granular cytoplasm and small intracystic papillae formed. The clear tumor cell clusters, similar as cystic lined tumor cells, were seen within pathological fibrous in almost all cases, and significant myofibroblastic proliferation was found in 14 cases. Immunohistochemically, the cysts lined epithelial cells and the clear tumor cell clusters were positive for epithelium markers, including CKpan(19/19), EMA(16/19) and CK7 (15/19); higher percentage of CAIX (17/19) and PAX8(15/19) than control groups, but lower percentage of CD10 (7/19), RCC (6/19) and AMACR(2/19); and all were negative for 34βE12, CD117 and CD68., Conclusions: Multilocular cysts, clear cells clusters of low Fuhrman grade within fibrous septa and capillary vessel proliferation under epithelium are important features of MCRCC. The united using of CAIX, CK7, CD10 and RCC is helpful for differentiating variable cystic renal tumor. MCRCC usually has an excellent prognosis, nephron sparing surgery is first recommended as a therapeutic strategy.

Papillary renal cell carcinoma (PRCC) includes two different morphological subtypes. The differences of genetics and ultrastructure of the two subtypes have been rarely reported. Also, new biomarkers related to the diagnosis and prognosis of PRCC have still not been well elucidated. Immunohistochemistry, fluorescence in situ hybridization (FISH) and transmission electron microscopy were used systematically to determine the characteristics of 56 cases of PRCC and to reveal new diagnostic and prognostic information. Type 1 PRCC presented higher expression rates of EMA and CK7, whereas type 2 presented a higher expression rate of CD10. New immunohistochemical markers, including: p504s, PAX-2, PAX-8 and CA-IX showed extensive immunostaining in PRCC. We first revealed a distinct immunostaining pattern of CA-IX, which was located in multiple foci in PRCC. All tumors had at least one chromosomal aberration including loss of Y, gains of 7 or 17. Gain of chromosome 17 was common in type 1; losses of chromosome 18, 11 and 8 appeared in type 2. Ultrastructurally, glycogen granules and secondary lysosomes were seen in type 1, mitochondria and smooth endoplasmic reticulum were scattered in type 2. Tumor subtype, nuclear grade, TNM stage, clear cell renal cell carcinoma (CCRCC) component and sarcomatoid elements, metastasis, CAIX expression, losses of chromosome 18 and 8 were related to poor outcome of PRCC. We conclude that the two subtypes of PRCC originate from different renal cells, and arise from partially common genetic pathways. EMA, CK7, CD10, p504s, PAX-2, PAX-8 and CA-IX are helpful markers in the differential diagnosis of PRCC. CA-IX expression, losses of chromosome 18 and 8 are new prognostic factors of PRCC., (Copyright © 2012 Elsevier GmbH. All rights reserved.)