In the WHO Classification of Tumours of the Urinary System and Male Genital Organs published in 2016, it was officially recommended that the percent of Gleason pattern 4 (GP4) be reported on pathology reports to better reflect the extent in Gleason score 7 tumors. In this study we assessed the reproducibility of reporting GP4 on prostate biopsies. We analyzed prospectively 422 cores containing GP4 from our consult cases over a period of 2.5 months. The percent pattern 4 was assigned to all the cases in 10% increments from 0% to 100% (with the addition of 5%) by 1 of 4 fellows in urological pathology and by the expert urological pathologist. Out of 422 cores, 32% were an exact match and 75% were within ±10% (weighted κ [κW] value 0.67). Cases were further stratified on the basis of (1) scattered versus clustered GP4 in the background of Gleason pattern 3, (2) continuous versus discontinuous tumor involvement, (3) cribriform/glomeruloid pattern only versus poorly formed/fused pattern versus mixed cribriform and poorly formed/fused pattern, and (4) total tumor involvement of the core (≤10% vs. >10% of the core). No significant differences were observed in the first 3 variables. However, in cases with ≤10% involvement of the core, 61% were within ±10% (κW=0.50) compared with cases with >10% involvement of the core, in which 78% were within ±10% (κW=0.70). In summary, we showed that assessment of percent GP4 was relatively reproducible, with substantial agreement within ±10% in cases. However, with <10% involvement of the core, it was more difficult to assess in smaller foci, with only moderate agreement. Given that in a small focus only a few glands of a given pattern can markedly affect the percent GP4, consideration should be given to not recording percent GP4 in small foci of Gleason score 7 tumors on needle biopsy.
Phosphaturic mesenchymal tumor (PMT) is a rare entity that presents as a paraneoplastic syndrome that causes tumor-induced osteomalacia (TIO). Most of these cases were located in the extremities. We report a case of a phosphaturic mesenchymal tumor arising in the left upper thigh. The tumor was discovered during the clinical workup of a patient complaining of osteomalacia symptoms with multiple fractures.
Inflammatory myofibroblastic tumor (IMT) is a rare neoplasm. Approximately 50 % of IMTs show an anaplastic lymphoma kinase (ALK) gene fusion resulting in ALK overexpression on immunohistochemistry (IHC). A novel anti-ALK monoclonal antibody (D5F3) has been suggested to be of superior sensitivity to the ALK1 antibody which is currently used. We compared the performance of D5F3 in detecting ALK protein expression in IMTs from various anatomic sites compared to the currently utilized ALK1. We selected 25 IMTs from our surgical pathology files (2005-2015). The novel rabbit monoclonal anti-human CD246 (clone D5F3) and the currently used mouse monoclonal anti-human CD246 (clone ALK1) were used for immunohistochemical staining (IHC) in an automated slide stainer. The percentage of immunoreactive tumor cells (0, <5 %, 5-50 %, >50 %) and cytoplasmic staining intensity (graded 0-3) were assessed and compared between the two antibodies. Fluorescence in situ hybridization (FISH) studies for ALK gene rearrangement were performed on 11 tumors. D5F3 antibody stained 76 % and ALK1 antibody stained 72 % of IMTs (p = 0.747). Compared to staining with ALK1, D5F3 stained a higher proportion of cases extensively (>50 % cells) (76 vs. 28 %, p < 0.001) and with high intensity (grade 3 76 % vs 0; p < 0.001). FISH and IHC findings (for both antibodies) were concordant in 9/10 (90 %) IMTs, in which results were informative. The novel anti-ALK rabbit monoclonal antibody (D5F3 clone) demonstrates superior overall performance in term of intensity and extent of staining of ALK protein in IMT. We found IHC staining with both antibody clones to correlate equally well with FISH results for detection of ALK rearrangement.
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