Metastatic spindle cell malignant melanoma with prominent microvilli

A metastatic spindle cell malignant melanoma with positive immunoreactivity for S-100 protein and HMB-45 antigen and the presence of premelanosomes is described in a lymph node of the neck 11 years after removal of a superficial spreading malignant melanoma from the arm. Ultrastructurally, long, slender microvilli created a pattern with great similarity to an anemone cell tumor. A more solid pattern without microvilli was also present. Despite the abundance of microvilli in the anemone part of the tumor, intracytoplasmic lumina were not observed. In addition, crystalline structures within enlarged mitochondria and intracisternal tubules were noted.