<p><b>OBJECTIVE</b>To study the histogenesis, pathologic features and
differential diagnosis of prostatic primary
signet ring cell carcinoma.</p><p><b>
METHODS</b>10 cases of the primary
signet ring cell carcinoma were detected from 262 cases of
prostate carcinomas diagnosed on
needle biopsy were investigated by routine pathological, immunohistochemical and histochemical
methods, and then compared with 10 cases of signet ring
cell carcinomas of the
stomach and
colon. 3 cases were studied with
electron microscopy.</p><p><b>RESULTS</b>9 cases of
prostate signet ring cell carcinoma were associated with concurrent high-grade conventional prostatic
carcinoma, but at least 25% of the
neoplasm consisted of signet ring
cells. Only one case was pure
signet ring cell carcinoma. Neoplastic signet ring
cells may be divided into two types the first type showed formation of intracytoplasmic lumina or
vacuole, and the second type had intracytoplasmic accumulation of excess PSA and/or PAP. Both types of signet ring
cells were negative for
mucin staining (AB/PAS and mucicarmine). Therefore they differed from signet ring
cell carcinomas of the
stomach and
colon.</p><p><b>CONCLUSIONS</b>Primary
prostate signet ring cell carcinoma is a low-differentiated
adenocarcinoma of a special histologic type, which arises from the
epithelial cells of the
prostate acinus. They can be distinguished from metastatic
signet ring cell carcinoma of the
stomach and
colon and also from vacuolate degeneration of conventional
carcinoma after endocrine or
radiation therapy.</p>