Metastatic malignant melanoma. A case study with unusual ultrastructure.

The unusual ultrastructure of a metastatic malignant melanoma is discussed. Light microscopy revealed most tumor cells to be nonpigmented, multinucleated giant cells. Electron microscopy demonstrated bizarre, cytoplasmic filaments void of melanin deposition. The internal structure of these filaments exhibited distinct periodicity similar to that seen in normal melanosomes.