Metastasis of primary signet ring cell carcinoma of prostate to bone marrow: A rare occurrence with review of literature.

We report a case of a 65-year-old male who presented with multiple enlarged intraabdominal lymph nodes with lytic lesions over pelvic and lumbar vertebrae. His serum prostate-specific antigen (PSA) was markedly raised. Bone marrow investigation revealed the presence of diffuse infiltration of single cells having hyperchromatic nuclei, moderate amount of eosinophilic cytoplasm, and eccentrically placed nuclei resembling signet ring cells. Hence, a diagnosis of metastatic signet cell carcinoma of prostate was made on bone marrow biopsy. This variant of prostatic carcinoma is very rare and accounts for only 2.5% of all prostatic adenoacarcinomas that make our case worth reporting. To emphasize the rare occurrence of this variant, we performed a Pubmed-based literature review of 25 years.