Melanomatous bone marrow invasion. Bone marrow biopsy specimen and aspirate from a patient with disseminated malignant melanoma. (a) Bone marrow biopsy specimens. The bone marrow is almost completely replaced by sheets of neoplastic cells with pleomorphic nuclei, prominent nucleoli, and abundant pink cytoplasm. Some malignant cells display prominent vacuolization (hematoxylin and eosin, original magnification × 200). (b) Bone marrow aspirate. Myeloid precursors containing multiple, irregular, darkly pigmented, melanin-containing vacuoles (Wright's stain, original magnification × 1,000). (c) Bone marrow biopsy specimen. The neoplastic cells are srongly reactive to HMB45 (immunoperoxidase, original magnification × 400). (Courtesy of Niyati Bhagwati, MD, Rommel Seno, MD, and Leslie Oleksowicz, MD, Montefiore Hospital and The Albert Einstein Cancer Center, 111 E 210th St, Bronx, NY 10467.)