Microscopic description and IHC:

The prostate is infiltrated by poorly differentiated neoplastic cells. The malignant cells have prominent nucleoli, moderate cytoplasm, and are positive for CK7, CD31, and D240. Mitotic figures are conspicuous. The cells are negative for multiple prostate specific markers (not pictured).

Discussion:

Given the clinical history of radiotherapy and immunohistochemical profile, epithelioid angiosarcoma is the best answer. CK7 positivity, as well as other cytokeratin positivity, has been described in epithelioid angiosarcoma. Urothelial carcinoma would not express CD31 or D240. Prostatic adenocarcinoma is eliminated by CK7 positivity and lack of positive prostate specific markers. The other answer choices are also eliminated by immunohistochemical profile and clinical history.

References:

Matoso, A., & Epstein, J. I. (2015). Epithelioid Angiosarcoma of the Bladder. The American Journal of Surgical Pathology, 39(10), 1377-1382.

Rosai, J., & Ackerman, L. V. (2004). Chapter 17 urinary tract: kidney, renal pelvis, and ureter - bladder and male urethra, Rosai and Ackerman's surgical pathology. Edinburgh: Mosby.

CASE IMAGES