WHO Classification of Tumours fifth edition: evolving issues in the classification, diagnosis, and prognostication of prostate cancer

Abstract

The fifth edition of the WHO Classification of Tumours of the Urinary and Male Genital Systems encompasses several updates to the classification and diagnosis of prostatic carcinoma as well as incorporating advancements in the assessment of its prognosis, including recent grading modifications. Some of the salient aspects include: (1) recognition that prostatic intraepithelial neoplasia (PIN)-like carcinoma is not synonymous with a pattern of ductal carcinoma, but better classified as a subtype of acinar adenocarcinoma; (2) a specific section on treatment-related neuroendocrine prostatic carcinoma in view of the tight correlation between androgen deprivation therapy and the development of prostatic carcinoma with neuroendocrine morphology, and the emerging data on lineage plasticity; (3) a terminology change of basal cell carcinoma to "adenoid cystic (basal cell) cell carcinoma" given the presence of an underlying MYB::NFIB gene fusion in many cases; (4) discussion of the current issues in the grading of acinar adenocarcinoma and the prognostic significance of cribriform growth patterns; and (5) more detailed coverage of intraductal carcinoma of prostate (IDC-P) reflecting our increased knowledge of this entity, while recommending the descriptive term atypical intraductal proliferation (AIP) for lesions falling short of IDC-P but containing more atypia than typically seen in high-grade prostatic intraepithelial neoplasia (HGPIN). Lesions previously regarded as cribriform patterns of HGPIN are now included in the AIP category. This review discusses these developments, summarising the existing literature, as well as the emerging morphological and molecular data that underpins the classification and prognostication of prostatic carcinoma.

Keywords: WHO Classification; pathology; prostate carcinoma.

Figure 1

Ductal adenocarcinoma [(A), higher power in (B)] with papillary and cribriform architecture in contrast to the large discrete glands of PIN‐like carcinoma (C,D). PIN‐like carcinoma with simple discrete glands lined by flat and tufted tall columnar epithelium (C). The absence of basal cells is highlighted by immunohistochemistry (IHC) [(D), p63, cytokeratin 34βE12 and AMACR cocktail]. Treatment‐related neuroendocrine prostatic carcinoma [(E), synaptophysin IHC in (F)]. Cords of cells with hyperchromatic crowded nuclei. Only rare gland formation is present [arrow in (E)]. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 2

Small cribriform glands with ≤12 luminal spaces (A) contrasting with large cribriform glands (B). Intraductal carcinoma of prostate with retention of basal cells and surrounding adjacent high‐grade invasive adenocarcinoma [(C), IDC‐P indicated by arrow; (D), IHC for p63, cytokeratin 34βE12 stained brown, and AMACR red]. Atypical intraductal proliferation (AIP) with loose cribriform proliferations and only minor cytological atypia (E). No necrosis is seen and basal cells are retained [(F), p63, cytokeratin 34βE12, and AMACR cocktail]. [Colour figure can be viewed at wileyonlinelibrary.com]