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Papillary renal cell carcinoma (PRCC) is well-recognized as a morphologically and molecularly heterogenous group of kidney tumors with variable clinical behavior. Our goal was to analyze a unique histologic pattern of PRCC we have observed in routine practice to evaluate for potential clinical significance or distinct molecular signature. We identified 42 cases of PRCC showing a morphologically distinct architecture characterized by numerous epithelial-lined cysts containing the papillary tumor (herein called “microcysts”), which are typically separated by fibrous stroma. Of the initial 42 case test set with microcystic features, 23 (55%) were stage pT3a or higher. Most tumors had strong and diffuse cytoplasmic immunoreactivity for CK7 (93%, 37/40) and AMACR (100%, 40/40). Fumarate hydratase staining was retained in all cases tested (39/39). We performed next-generation sequencing on 15 of these cases with available tissue and identified chromosomal alterations commonly reported in historically “type 1” PRCC, notably multiple chromosomal gains, particularly of chromosomes 7 and 17, and METalterations. However, alterations in pathways associated with more aggressive behavior (including SETD2, CDKN2A, and members of the NRF pathway) were also identified in 6 of 15 cases tested (40%). Given this molecular and immunophenotypic data, we subsequently reviewed an additional group of 60 consecutive pT2b-pT3 PRCCs to allow for comparisons between cases with and without microcysts, to assess for potential associations with other recently described histologic patterns (ie, “unfavorable architecture”: micropapillary, solid, and hobnail), and to assess interobserver reproducibility for diagnosing architectural patterns and grade. Of the total combined 102 PRCCs, 67 (66%) had microcystic architecture within the intrarenal component but were commonly admixed with other patterns (39% had micropapillary, 31% solid, and 31% hobnail). Twenty-seven cases (26%) had metastatic disease, and 24 of these 27 (89%) had microcystic architecture in the intrarenal tumor. Within the pT3 subset, 21 of 22 cases with metastases (95%) had extrarenal invasion as either individual microcysts in renal sinus fat or aggregates of microcysts bulging beyond the confines of the capsule. Backward elimination and stepwise regression methods to detect features significantly associated with adverse outcome identified solid architecture (hazard ratio [HR]: 6.3; confidence interval [CI]: 2.1-18.8; P=0.001), hobnail architecture (HR: 5.3; CI: 1.7-16.7; P=0.004), and microcystic architecture at the tumor-stromal interface (HR: 4.2; CI: 1.1-16.7; P=0.036) as strongest. Of architectural patterns and grade, the microcystic pattern had a substantial interobserver agreement (κ score=0.795) that was highest among the 6 observers. In summary, PRCCs with microcystic architecture represents a subset of historically “type 1” PRCC with a predilection for morphologically distinctive extrarenal involvement and metastatic disease. Microcysts co-vary with other “unfavorable” architectural patterns also associated with higher risk for aggressive disease (ie, micropapillary, hobnail, and solid), but microcysts were more common and have superior interobserver reproducibility. These findings suggest that microcystic PRCC should be recognized as a potentially aggressive histologic pattern of growth in PRCC.

Bayes's theorem arose from a posthumous publication in 1763 by Thomas Bayes, a non-conformist minister from Tunbridge Wells. Although it gives a simple and uncontroversial result in probability theory, specific [...]

Immunohistology is essential to the practice of modern surgical and cytopathology. There are 3 major types of immunohistologic services provided in clinical practice: traditional immunohistochemistry, morphometric analysis of tumor immunohistochemistry, and immunofluorescence. Proper Current Procedural Terminology coding for these services has been updated to reflect current medical practice. Subsequent to changes in the Current Procedural Terminology coding structure for these services, the valuation of these services have been reviewed by the American Medical Association/Specialty Society Relative Value Update Committee and new valuations instituted by the Centers for Medicare and Medicaid Services. Although valuations for services may be established, the circumstances of payment may be affected by Medicare Contractor’s Local Coverage Determinations or service limits imposed by the National Correct Coding Initiative.

Health care reform has accelerated as the existing health care system undergoes continuing financial stress. Medicare’s new value-based payment system, commonly referred to as MACRA, provides opportunities for physicians to participate in this new system in a variety of ways. However, many of the value-based adjustments are based on existing valuations of services through traditional mechanisms. To achieve appropriate valuation of pathologist’s services in the new payment models, it is imperative that we continue to achieve proper valuation of services through the traditional mechanisms.

Early recognition of BK viral nephropathy is essential for successful management. Our aim in this study was to evaluate a novel fluorescence in situhybridization (FISH) assay for detection of BK virus in renal transplant biopsies in the context of standard detection methods. Renal allograft biopsies (n= 108) were analyzed via H&E, immunohistochemistry (IHC) for simian virus 40, and FISH for BK virus. BK virus was detected in 16 (14.8%) cases by H&E, 13 (12%) cases by IHC, 18 (16.6%) cases by FISH, and 19 (17.6%) cases by real-time PCR; 24 of 108 showed a discrepancy in ≥1 testing modalities. Comparison of H&E, IHC, and FISH showed no statistical difference in detection of BK virus. However, performing comparisons between the different tissue-based assays in the context of plasma or urine real-time PCR results showed significant improvement in detection of BK by FISH over H&E (P= 0.02) but not IHC (P= 0.07). This novel FISH-based approach for BK virus identification in renal allograft biopsy tissue mirrored real-time PCR results and showed superior performance to detection of inclusions by H&E. Therefore, use of FISH for BK virus detection in the setting of renal allograft biopsy is a useful and sensitive detection method and could be adopted in any laboratory that currently performs FISH analysis.

BK virus nephropathy is not an infrequent complication of renal transplantation associated with high rates of graft loss. Although antibodies against SV40 antigen detect different viruses of the polyomavirus family, immunohistochemistry is widely used to confirm the diagnosis of BK virus nephropathy in renal biopsies. Here we aimed to validate the novel silver-enhanced in situ hybridization (SISH) technique for the automated detection of BK virus in renal transplant biopsies. Two different patient cohorts were included. Twenty-nine consecutive patients suspicious for BK virus infection were investigated by SISH and chromogenic in situ hybridization. An additional 26 renal biopsies positive by SV40 immunohistochemistry from 19 patients were analyzed by SISH. Polyomavirus DNA serum levels, as determined by nested PCR analysis, were available for all of these patients. The presence of BK virus DNA in renal tubular cells was identified in 5 of the suspicious cases by both, SISH and chromogenic in situ hybridization . One additional patient was only positive in the SISH. In the second cohort, SISH was positive in all SV40 positive biopsies, but SISH signals were less extensive than SV40 immunohistochemistry. Our results show that the BK virus SISH is an ancillary tool for the detection of polyomavirus DNA in renal biopsies using bright-field microscopy. However, its diagnostic value in comparison with standard immunohistochemistry seems to be limited.

Wegener granulomatosis (WG) is a systemic disease that is often associated with an immune-mediated form of glomerulonephritis (GN). Renal disease most often manifests as microscopic hematuria with or without red blood cell or mixed cellular casts, proteinuria, and an elevated serum creatinine concentration.

The independent prognostic importance of microscopic bladder neck involvement by prostate cancer in radical prostatectomy is questionable. We studied a cohort of 1845 patients to determine the significance of microscopic bladder neck involvement. Bladder neck involvement was defined as prostate cancer present within the coned bladder neck. We further categorized the cases as ‘true bladder neck involvement’ and ‘false bladder neck involvement.‘ True bladder neck involvement required prostate cancer within thick smooth muscle bundles without intermixed benign prostatic glands. False bladder neck involvement was characterized by prostate cancer intermixed with benign prostatic glands. Bladder neck involvement was analyzed in relation to preoperative serum prostate-specific antigen (PSA) level, extraprostatic extension, seminal vesicle involvement, positive surgical margin, lymph node involvement, radical prostatectomy Gleason score, and tumor volume. Of the 90 patients (4.9%) with microscopic bladder neck involvement, 63 were further classified as true bladder neck involvement and 27 as false bladder neck involvement. In univariate model, both types of bladder neck involvement (P<0.001), true (P<0.001), and false (P=0.040), were significantly associated with increased PSA-recurrence risk compared to bladder neck negative cases. In multivariate model the PSA-recurrence relative risk associated with bladder neck involvement (true or false) was not a significant independent prognostic factor. Extraprostatic extension, seminal vesicle involvement, positive surgical margin, lymph node involvement, PSA, and Gleason score were significant independent predictors of PSA recurrence. The time to biochemical recurrence in patients with bladder neck involvement was similar to that of pT2 with positive surgical margin or pT3a with negative surgical margin patients (Kaplan–Meier curves). Bladder neck involvement was associated with other adverse pathologic features, but was not an independent predictor of PSA recurrence. In view of the previous and current data, the staging system for bladder neck involvement should be revised and patients may be best categorized as having pT3a disease.

Antibody-mediated renal allograft rejection has become increasingly recognized and more clearly defined through the use of flow cytometry cross-matching and the deposition of C4d in renal allograft biopsies. All of the cases reported thus far have developed an antibody within 10 years of transplantation, and many lacked HLA and/or donor specificity.The present patient developed an anti-HLA donor-specific antibody between the 22nd and 30th year after a living-related renal transplant. At the 30th year post-transplantation, she experienced a rise in the serum creatinine from 0.7 to 1.9 mg/dL associated with transplant biopsy C4d deposition in peritubular capillaries and glomeruli. After the replacement of azathioprine with mycophenolate mofetil, and six apheresis treatments followed by two infusions of IVIG, the renal function stabilized at 1.9 mg/dL, 33 years after transplantation. Antibody-mediated rejection must be considered as a possible cause or renal allograft dysfunction at all time periods after transplantation.

Antibody‐mediated renal allograft rejection has become increasingly recognized and more clearly defined through the use of flow cytometry cross‐matching and the deposition of C4d in renal allograft biopsies. All of the cases reported thus far have developed an antibody within 10 years of transplantation, and many lacked HLA and/or donor specificity.