Prostatic Carcinoma with Abundant Xanthomatous Cytoplasm

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Abstract
Foamy gland carcinoma, an unusual variant of prostate carcinoma, is characterized by abundant xanthomatous cytoplasm. We studied 38 needle biopsies in which at least one core contained cancer with >20% foamy morphology. On average, each cancer was 72% foamy, and 11 cancers were entirely foamy. In addition to the characteristic cytoplasm, 20 cases had abundant intraluminal dense pink amorphous secretions. Nuclear enlargement and prominent nucleoli were either absent or rare in 23 (61%) and 27 (71%) of foamy gland carcinomas, respectively. High-molecular-weight cyto-keratin stains were done in 20 cases; 19 foamy gland carcinomas were negative, confirming the diagnosis of carcinoma and one case had keratin staining inconsistent with a known benign pattern. Of the 27 cases with associated ordinary gland carcinoma on needle biopsy, 26 (96%) were Gleason sum >4. Subsequent radical prostatectomy (RP) and transurethral resection demonstrating cancer were available in 17 cases. Of the 15 subsequent RPs, only five were organ-confined and only one was Gleason sum <5. The cancers in the RP group ranged from 1 to 90% foamy (mean, 39%). Foamy gland carcinoma must be recognized as carcinoma by its abundant foamy cytoplasm, its architectural pattern of crowded or infiltrative glands, and frequently present pink acellular secretions. The more typical features of adenocarcinoma, nuclear enlargement and prominent nucleoli, are frequently absent. Its relatively benign cytology makes this lesion difficult to recognize as carcinoma; 74% of our cases were seen in consultation. Despite its benign cytology, foamy gland carcinoma is best classified as intermediate-grade carcinoma.