Occult Metastatic Prostate Carcinoma Presenting With Decompensated Heart Failure and Bicytopenia.

Decompensated heart failure (DHF) may occasionally conceal an underlying systemic malignancy. Persistent hematological abnormalities, particularly thrombocytopenia and markedly elevated alkaline phosphatase (ALP), extending beyond the acute phase of illness warrant systematic evaluation for bone marrow pathology or infiltrative disease, irrespective of the presenting diagnosis. A 53-year-old man with no prior comorbidities presented with DHF, bicytopenia (anemia and thrombocytopenia), and markedly elevated ALP. He developed disseminated intravascular coagulation (DIC) during hospitalization, managed with fresh frozen plasma (FFP), platelet concentrates, and cryoprecipitate, with subsequent resolution; however, thrombocytopenia and ALP elevation persisted. Bone marrow examination revealed infiltration by metastatic adenocarcinoma. Despite comprehensive evaluation including gastrointestinal endoscopies, contrast-enhanced computed tomography (CT), and 18-fluorodeoxyglucose positron emission tomography-CT (18-FDG PET-CT), the primary site remained elusive in the setting of multiple elevated tumor markers: prostate-specific antigen (PSA), carcinoembryonic antigen (CEA), and carbohydrate antigen (CA) 19-9. Immunohistochemistry of the bone marrow biopsy demonstrated positivity for cytokeratin (CK) and NKX3.1, establishing prostatic origin. Subsequent prostate biopsy confirmed left-lobe prostatic adenocarcinoma with a Gleason score of 4+3=7 (Grade Group 3), tumor comprising 70% of the biopsy core, and perineural invasion, consistent with high-risk locally advanced disease. The patient was commenced on androgen deprivation therapy (ADT). Persistent thrombocytopenia and markedly elevated ALP may represent the sole initial manifestation of occult metastatic prostate cancer, even in young patients with no urological symptoms. Immunohistochemistry, particularly NKX3.1, is indispensable in establishing prostatic origin when the primary site remains radiologically occult after comprehensive investigation.