Prostatic foamy gland carcinoma with aggressive behavior: clinicopathologic, immunohistochemical, and ultrastructural analysis.

Foamy gland carcinoma is a recently described histologic variant of prostatic adenocarcinoma characterized by abundant foamy cytoplasm and minimal cytologic atypia. The biologic behavior and biochemical nature of the foamy adenocarcinoma cells are unknown. Six cases of prostatic adenocarcinoma with marked foamy appearance were identified from radical prostatectomies. Clinicopathologic, histochemical, immunohistochemical, and ultrastructural analyses were conducted. The patients ranged in age from 50 to 73 years (mean age, 65 years) with preoperative serum prostate-specific antigen levels ranging from 2.7 to 37.5 ng/mL (mean, 15.2 ng/mL). All six cases were bilateral high-volume tumors. Five of six patients had high-grade tumors with extraprostatic extension. The foamy tumor cells were negative for mucin and lipid stains, but were positive for colloidal iron and Alcian blue stain. Ultrastructurally, the foamy cells displayed numerous intracytoplasmic vesicles and numerous polyribosomes. The authors conclude that the foamy appearance of these tumor cells is the result of the presence of numerous intracytoplasmic vesicles, and not the result of the presence of lipid or neutral mucin. This study illustrates that foamy gland carcinoma is a distinctive histologic variant of prostatic adenocarcinoma and is often associated with an aggressive behavior despite its deceivingly benign histologic appearance.