Pathologists are increasingly exposed to prostate biopsies with small atypical foci, requiring differentiation between adenocarcinoma, atypical small acinar proliferation suspicious for malignancy, and a benign diagnosis. We studied the level of agreement for such atypical foci among experts in urologic pathology and all-round reference pathologists of the European Randomized Screening study of Prostate Cancer (ERSPC). For this purpose, we retrieved 20 prostate biopsies with small (most <1 mm) atypical foci. Hematoxylin and eosin-stained slides, including 10 immunostained slides were digitalized for virtual microscopy. The lesional area was not marked. Five experts and 7 ERSPC pathologists examined the cases. Multirater κ statistics was applied to determine agreement and significant differences between experts and ERSPC pathologists. The κ value of experts (0.39; confidence interval, 0.29-0.49) was significantly higher than that of ERSPC pathologists (0.21; confidence interval, 0.14-0.27). Full (100%) agreement was reached by the 5 experts for 7 of 20 biopsies. Experts and ERSPC pathologists rendered diagnoses ranging from benign to adenocarcinoma on the same biopsy in 5 and 9 biopsies, respectively. Most of these lesions comprised between 2 and 5 atypical glands. The experts diagnosed adenocarcinoma (49%) more often than the ERSPC pathologists (32%) (P<0.001). As agreement was particularly poor for foci comprising <6 glands, we would encourage pathologists to obtain intercollegial consultation of a specialized pathologist for these lesions before a carcinoma diagnosis, whereas clinicians may consider to perform staging biopsies before engaging on deferred or definite therapy. Copyright

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Keywords Diagnostics, Interobserver variation, Pathology, Prostate biopsy, Prostate cancer, Virtual microscopy
Persistent URL dx.doi.org/10.1097/PAS.0b013e3181c7997b, hdl.handle.net/1765/27766
Citation
van der Kwast, Th.H, Evans, A, Lockwood, G.A, Tkachuk, D, Bostwick, D.G, Epstein, J.I, … Srigley, J. (2010). Variability in diagnostic opinion among pathologists for single small atypical foci in prostate biopsies. American Journal of Surgical Pathology, 34(2), 169–177. doi:10.1097/PAS.0b013e3181c7997b