Sarcomatoid Carcinoma of the Prostate With Both Chondrosarcomatous and Osteosarcomatous Differentiation Following Androgen Deprivation Therapy: A Case Report and Diagnostic Considerations

BackgroundSarcomatoid carcinoma of the prostate is a rare and aggressive biphasic malignancy, typically arising in the setting of prior prostatic adenocarcinoma. Prominent heterologous differentiation may obscure its epithelial origin and lead to diagnostic confusion with primary mesenchymal tumors.Case presentationWe report an 80-year-old man with a history of metastatic prostate adenocarcinoma treated with androgen deprivation therapy, who presented with acute urinary obstruction and low prostate-specific antigen levels. Transurethral resection revealed a highly heterogeneous tumor composed of extensive cartilaginous and high-grade sarcomatoid components, including both chondrosarcomatous and osteosarcomatous differentiation. Despite thorough histopathological examination, no epithelial component was identified. Prior pathology confirmed adenocarcinoma up to 9 months earlier, with evidence of sarcomatoid transformation emerging in recent specimens. Immunohistochemistry supported mesenchymal differentiation. Based on clinicopathological correlation, a diagnosis of sarcomatoid carcinoma of the prostate with heterologous differentiation was established.ConclusionThis report highlights a significant diagnostic pitfall in which sarcomatoid carcinoma may mimic primary sarcoma when the sarcomatoid component predominates and epithelial elements are absent. It also underscores the potential role of androgen deprivation therapy in tumor dedifferentiation and the limitations of PSA in monitoring disease progression. Awareness of this entity is essential for accurate diagnosis and appropriate clinical management.