PATHOLOGY

Basal Cell Carcinoma of the Prostate: A Clinicopathologic Study of 29 Cases
Ali TZ, Epstein JI
Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, MD, USA
Am J Surg Pathol. 2007;31:697-705

• We studied 29 cases of basal cell carcinoma of the prostate including what others call adenoid cystic carcinoma of the prostate. Patients’ age ranged from 42 to 89 (mean 69) years. The most common methods of diagnosis was transurethral resection (TURP) (n=29) and needle biopsy (n=9). In 28/29 cases, slides were reviewed and 24 (86%) cases showed more than 1 pattern: adenoid cysticlike (AC-P) pattern and small solid nests with peripheral palisading were the most predominant patterns, each seen in 18 cases (64%). Other patterns included: basal cell hyperplasialike in 9 cases (32%); small tubules occasionally lined by a hyaline rim in 9 cases (32%), with 4 of these cases also demonstrating intermingling cords of cells; and large solid nests in 8 cases (28.5%), 5 of which had central necrosis. Fourteen cases of small nests and tubules were centrally lined by eosinophilic cells. Desmoplasia was noted in 20 (71%) cases. Infiltration around benign glands was seen in 10 (36%) cases, with predominantly small nests and AC-P. Invasion of thick muscle bundles of the bladder neck was seen in 10 of 21 TURP cases. Perineural invasion was noted in 3 cases with AC-P and 1 case of small basaloid nests. Perineural and vascular invasion was seen in 2 basal cell carcinomas with large basaloid nests. Mitoses ranged from 0 to 60/10 hpf (mean=4). bcl2 was diffusely positive in 22/24 (92%) cases. Ki67 ranged from 2% to 80% (mean=23%). Ki67 > or =20% was seen in 13 (56.5%) cases, including all patterns except small solid nests. Basal cell markers (HMWCK, p63) either: (1) highlighted multiple layers of cells in 15/25 (60%) cases with sparing of the inner most luminal layer; (2) labeled just the outermost layers in 6/25 (24%) cases; or (3) reacted with only a few scattered cells in 4/25 (16%) cases (3 with large solid nests with central necrosis, 1 with tubules and cords). Seven patients had RP with: 5/7 showing extraprostatic extension with 1/5 also showing seminal vesicle involvement and 2/5 also with a positive margin; 1/7 having organ confined disease; and 1/7 showing no residual disease. An additional 11 cases showed extraprostatic extension on TURP with bladder neck invasion (n=10) or periprostatic adipose tissue invasion (n=1). Of 29 (65.5%) cases, 19 had follow-up > 1 year with a mean of 4.3 years (1 to 19 y). Of 19 (77%) cases, 14 had no evidence of disease after 1 to 19 (mean 5.8) years. Of 19 patients, 4 locally recurred with 2 after TURP, 1 after enucleation, and 1 after RP. Metastases developed in 4/29 patients: 1 in lung, 1 in lung and liver, 1 in lung, bone and liver, 1 in penile urethra. Basal cell carcinomas are rare tumors with a broad morphologic spectrum. These tumors predominantly show an indolent course with local infiltrative behavior. A small subset behaves aggressively with local recurrences and distant metastases. The most common morphology among those with an aggressive behavior is large solid nests more often with central necrosis, high Ki67%, and less staining with basal cell markers.
  
  
• Editorial Comment
  Basal and stem cells comprise the proliferative compartment of the prostatic acinus. There is a spectrum of basal cell lesions including typical hyperplasia, atypical hyperplasia, adenoma, and carcinoma (or adenoid cystic carcinoma). The latter is a rare tumor initially considered with an indolent biologic potential (1). In 2003, Iczkowski et al. (2) published the largest series at that time calling attention to the potential aggressiveness of this tumor requiring ablative therapy. From a total of 19 patients, 54 (21%) developed metastases.
  Ali and Epstein’s is the largest series so far of basal cell carcinoma (or adenoid cystic carcinoma) of the prostate. Of a total of 29, 19 patients had follow-up >1 year: 14 patients had no evidence of disease after 1 to 19 (mean 5.8 years); 4 locally recurred and 4 developed metastases.
  The authors conclude that these tumors predominantly show an indolent course with local infiltrative behavior. A small subset behaves aggressively with local and distant metastases. The most common morphology among those with aggressive behavior is large solid nests more often central necrosis, high Ki67%, and less staining with basal cell markers.

References
1. Young RH, Frierson Jr HF, Mills SE, Kaiser JS, Talbot WH, Bhan AK. Adenoid cystic-like tumor of the prostate gland. A report of two cases and review of the literature of “adenoid cystic carcinoma” of the prostate. Am J Clin Pathol 1988;89:49-56.
2. Iczkowski KA, Ferguson KL, Grier DD, Hossain D, Banerjee SS, McNeal JE, Bostwick DG. Adenoid cystic/basal cell carcinoma of the prostate: Clinicopathologic findings in 19 cases. Am J Surg Pathol 2003;27:1523-29.

Dr. Athanase Billis
Full-Professor of Pathology
State University of Campinas, Unicamp
Campinas, São Paulo, Brazil
E-mail: athanase@fcm.unicamp.br