ABSTRACT: Sarcomatoid carcinoma of the prostate is a rare entity constituting less than 0.1% of primary malignant tumors of the prostate. This malignancy is characterized by the presence of both glandular and sarcomatoid components, posing unique challenges in its diagnosis and management. We describe the case of a 66-year-old man who presented with a two-month history of left-sided chest pain and diffuse lower backache. Imaging revealed a mass lesion involving the prostate with widespread bone metastasis, and the serum prostate-specific antigen (PSA) level was 11.6 ng/ml. Subsequent immunohistochemical analysis confirmed sarcomatoid carcinoma of the prostate. The diagnosis and management of sarcomatoid carcinoma of the prostate are challenging due to its rarity, unusual presentation, and biphasic histologic nature. This aggressive malignancy carries a dismal prognosis and should be considered in the differential diagnosis of patients presenting with bone metastases and disproportionately low PSA levels.

Impact statement: This case highlights the importance of considering sarcomatoid carcinoma of the prostate in atypical presentations of metastatic prostate malignancy with disproportionately low PSA levels.

Key words: Immunohistochemistry; prostatic neoplasms; prostate-specific antigen; prognosis; sarcomatoid.