Answer: C. Prostatic infarct with reactive urothelium

Histology: Multiple prostatic chips have areas at low magnification with recent hemorrhage. In some of the chips there is infarcted tissue with ghosts of tubules. Surrounding these infarcts are nests with a urothelial appearance. Cytologically, some of the urothelial-appearing cells are moderately atypical with scattered mitotic figures identified. In other chips no infarcted tissue is noted but the same nests are seen amongst recent hemorrhage. Some of the nests contain focal necrosis in the center of nests with neutrophils and acellular debris.

Discussion: Prostatic infarcts are more commonly seen on TURPs done for BPH but can occasionally be seen on needle biopsy. It can markedly elevate serum PSA levels. On TURP, the lesion one can appear lobular with zonation. In the center of the infarct there is acute coagulative necrosis and recent hemorrhage with adjacent reactive epithelial nests. Progressing away from the infarct, there is more mature squamous metaplasia with fibrosis. The zonation is not as easily identified on biopsy, and likewise the needle biopsy may not sample the central infarct but only the edge of the infarct with the reactive epithelium. If one focuses on the epithelial nests, then one will likely misdiagnose the lesion as infiltrating carcinoma. However, if one first steps back to assess the overall lesion and notes that the nests are occurring associated with recent hemorrhage within the stroma, and that this is not the overall setting for urothelial carcinoma but is typical for a prostatic infarct, then the correct diagnosis can be made. Necrosis is also not common in nests of urothelial carcinoma and when present typically lacks neutrophils and central debris, as seen in prostatic infarcts.