Prostate Carcinoma with Squamous Differentiation: An Analysis of 33 Cases

Background: Only sporadic cases of prostate carcinomas with squamous differentiation have been reported. Design: The files of two institutions were reviewed for prostate cancers with squamous differentiation. Results: A total of 33 cases were studied. The average age at diagnosis was 68 years (range 49-86 years). The most common presenting symptoms included bladder outlet obstruction and dysuria. Thirteen men had a positive digital rectal examination. Diagnosis was made by needle biopsy (n = 23); transurethral resection of the prostate (n = 5); needle and transurethral resection of the prostate (n = 1); transurethral resection of the bladder (n = 1); or biopsy of metastases (n = 3). In 21 of 33 cases, there was a prior diagnosis of adenocarcinoma of the prostate; 8 patients were treated with hormones, 4 were treated with radiation, and 1 received both radiation and hormone therapy. Of the 12 men without a prior diagnosis of adenocarcinoma, 2 patients had received hormonal therapy for benign prostatic hyperplasia. Eight of 33 cases were pure squamous carcinomas. The remaining cases were adenosquamous carcinoma (n = 16), adenosquamous and urothelial carcinoma (n = 3), and adenosquamous carcinoma and sarcoma (n = 6). The squamous carcinoma component of these mixed cases averaged 40% of the tumor volume (range 5%-95%) and had a range of cytologic atypia (mild [n = 6], moderate [n = 17], severe [n = 10]). In the 25 cases with adenocarcinoma, the glandular component tended to be high-grade (Gleason grade >6 in 19 cases). Immunohistochemistry for prostate specific acid phosphatase and prostate specific antigen was positive in a large percentage of the adenocarcinomas (85% and 75%, respectively) and only very focally positive in 12% of the squamous carcinomas. 34βE12 was diffusely positive in >95% of the squamous carcinomas and only focally positive in <10% of the adenocarcinomas. Cytokeratins 7 and 20 did not differentiate the squamous and adenocarcinoma components. Follow-up was available on 25 of 33 cases, with the average survival being 24 months (range 0-63 months). Conclusion: Squamous differentiation in prostate cancer is uncommon, often but not necessarily arising in the setting of prior hormone or radiation therapy, and is associated with a poor prognosis. In addition to pure squamous cell carcinoma and adenosquamous cancer, other patterns may be seen. Whereas the adenocarcinoma component is typically high grade, the squamous component has a wide range of differentiation.