Diagnostic dilemmas of squamous differentiation in prostate carcinoma case report and review of the literature

Abstract

We report a case of pure squamous cell carcinoma involving the prostate and urinary bladder and describe the diagnostic dilemmas that we faced in trying to determine its origin. The patient was diagnosed ten years ago with prostatic adenocarcinoma treated with radioactive seed implantation. During the last year he also underwent a TURP procedure for urinary obstruction complicated by multiple infections. Postsurgery, the patient developed colo-urethral fistula and decision to perform cystoprostatectomy was taken. Excision illustrated a tumor mass replacing the entire prostate that microscopically proved to be squamous cell carcinoma. The challenge that we encountered was to determine its origin, the possibilities being divergent differentiation from adenocarcinoma post radiation therapy, de novo neoplasm or urothelial carcinoma with extensive squamous differentiation. Our literature review showed also that the etiology of prostatic squamous carcinoma is still unclear. We present our approach in an attempt to solve this dilemma.

Figure 1

1A) Infiltrating tumor mass forming nests and cords. 1B) Large, cohesive cells, with abundant glassy eosinophilic cytoplasm and well defined cell borders; focal keratinization. 1C) Focal tumor necrosis. 1D) Poorly differentiated cells with high grade nuclei infiltrating singly into the stroma. To view the virtual glass slide image for this figure please see here http://diagnosticpathology.slidepath.com/webViewer.php?snapshotId=1304063584.

Figure 2

2A) Tumor extending into seminal vesicles. 2B) Lymphovascular invasion. 2C) Perineural invasion. 2D) Areas of necrosis with calcifications consistent with therapy effect. To view the virtual glass slide image for this figure please see here http://diagnosticpathology.slidepath.com/webViewer.php?snapshotId=1304063622.

Figure 3

3A) Hyperplastic urothelium with focal frond-like proliferation. The urothelial cells were slightly enlarged but the nuclear to cytoplasmic ratio was maintained and the nuclear polarity was preserved. 3B) Squamous cell carcinoma infiltrating lamina propria and detrusor muscle. 3C) Squamous cell carcinoma extending, focally, into the urothelial mucosa.

Figure 4

4A) Viable neoplastic cells staining positive for AMACR. 4B) Endothelial cells in the vessels adjacent to the tumor showing focal nuclear AMACR positivity.

Figure 5

Our proposed algorithm for work-up of squamous cell carcinoma involving the prostate.