Disseminated Bone Marrow Carcinomatosis Due to Malignant Melanoma of Unknown Primary Origin

An 80-year-old woman was admitted to our hospital due to appetite loss and vomiting. A blood examination showed liver disorder with disseminated intravascular coagulation. All tumor markers and hepatitis virus markers were negative. Contrast-enhanced computed tomography did not show tumor lesions, bone lesions, lymphadenopathies, or thrombosis. A bone marrow biopsy revealed large, atypical cells with brown pigmentation and positive immunostaining for HMB-45, S100 proteins, and CD79a without myeloid or lymphoid markers. We experienced a case of disseminated carcinomatosis of the bone marrow due to malignant melanoma of unknown primary origin.