Study finds intraprostatic heterogeneity in mismatch repair-deficient prostate cancer

A single-institution study evaluated 32 primary, treatment-naive mismatch repair-deficient (MMRd) prostatic adenocarcinomas, finding cases spanned grade groups 2 through 5 and frequently showed intraductal or invasive cribriform features. Germline testing in 15 cases identified Lynch syndrome in 5, and MMR immunohistochemistry across multiple tissue blocks in 14 cases showed discordant MMR status between tumor foci in 8, with deficiency consistently confined to the highest-grade focus. The authors state these findings indicate a broader clinicopathologic spectrum of primary MMRd prostate cancer than previously recognized and highlight the importance of evaluating the highest-grade tumor focus when assessing multifocal disease.

Most relevant for: Relevant to evaluation of multifocal primary prostate cancer specimens and decisions around mismatch repair testing and germline Lynch syndrome assessment.

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