Malignant Melanoma Infiltrating the Bone Marrow

Malignant melanoma with infiltration into the bone marrow is seldom reported in the literature, for they are exceedingly rare. The primary site is not always apparent and a sizeable number of cases have been attributed to an occult primary. Metastasis to bone marrow is a terminal event usually occurring in stage IV of the disease and can be a focus of residual tumor cells which can cause a relapse. The current documentation is of a case of melanoma occurring as a rectal primary with anemia, thrombocytopenia, and leukoerythroblastic reaction. The marrow aspirates and trephine biopsy showed round to spindle-shaped malignant cells with intracytoplasmic brown-black coarse pigment, suggestive of melanin. The patient was diagnosed with stage IV melanoma but was lost for follow-up. The recognition of such an entity is important for both pathologists and clinicians alike. This case is being reported for the novelty of such an occurrence.