Case of the Week

2021-39/ September 27

Contributors: Jonathan Lee, William Lau, Reza Alaghehbandan

A man in his late 80s presented with urinary retention and a PSA of 2.2 ng/mL. He underwent a TURP. On cystoscopy, he was noted to have abnormal tissue at the base of the prostate that had a papillary appearance.

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5 photo(s) Updated on: September 25, 2021

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GATA3

GATA3

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NKX3.1

NKX3.1

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Quiz

1. What is the correct diagnosis?

a) High-grade papillary urothelial carcinoma

b) High-grade prostatic adenocarcinoma with pseudopapillary features

c) Metastatic colonic adenocarcinoma

d) Metastatic solid-pseudopapillary carcinomas of the pancreas

Histologic sections show a high-grade malignancy with papillary-appearing structures containing central blood vessels. The neoplastic cells have pleomorphic large irregular hyperchromatic nuclei and eosinophilic cytoplasm with frequent mitoses and apoptotic bodies. The neoplastic cells show strong, diffuse NKX3.1 nuclear staining and are negative for GATA3.

Pseudopapillary high-grade prostatic adenocarcinoma is a rare and unusual morphologic variant. In daily practice, a common diagnostic challenge on transurethral resection of prostate (TURP) specimens is in differentiating a poorly-differentiated urothelial carcinoma of the bladder and a poorly-differentiated prostatic adenocarcinoma. High-grade prostatic adenocarcinoma can have overlapping morphologic features with high-grade urothelial carcinoma. Such a distinction is highly critical and carries significant therapeutic implications.

The pseudopapillae occur in areas where prostate adenocarcinoma becomes loosely cohesive, losing the normal architecture of sheet and/or nests. The fragmentation of the tumor with more cohesive areas preserved around blood vessels mimics the fibrovascular cores of true papillae. It is important to have a high index of suspicion for poorly-differentiated malignancies involving the prostatic urethra, as they could be either of urothelial or prostatic origin. In such cases, one needs a low threshold for performing immunohistochemical staining (i.e., NKX3.1, GATA3). A recent study showed negative TERT mutations in high-grade prostatic adenocarcinoma which mimics urothelial carcinoma, supporting the notion that TERT promoter mutations are absent in prostate carcinoma.

1. Gordetsky J, Epstein JI. Pseudopapillary features in prostatic adenocarcinoma mimicking urothelial carcinoma: a diagnostic pitfall. Am J Surg Pathol. 2014 Jul;38(7):941-5.

2. Alaghehbandan R, Vanecek T, Trpkov K, Comperat E, Kristiansen G, Svajdler M, Cempirkova D, Pavlovsky M, Pivovarcikova K, Stehlikova A, Hora M, Michal M, Hes O. High-grade Adenocarcinoma of the Prostate Mimicking Urothelial Carcinoma is Negative for TERT Mutations. Appl Immunohistochem Mol Morphol. 2019 Aug;27(7):523-528.

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The Genitourinary Pathology Society (GUPS) was formed with the vision of advancing the care of patients with urologic diseases through enhancements of best practices, research, and education in the subspecialty of Urological Pathology.

GUPS is an official Companion Society of the United States and Canadian Academy of Pathology (USCAP).

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