Ultrastructural study of superficial spreading melanoma and benign simulants.

Ultrastructural examination of the intraepidermal component of superficial spreading melanomas (SSM) and benign melanocytic lesions was undertaken to determine the diagnostic value of electron microscopy in clinically "borderline" melanoma problems. Seventeen SSMs and ten benign melanocytic nevi and lentigenes which clinically resembled melanoma were studied. Melanocytes of the intraepidermal component of the SSMs showed a greater tendency for abnormal melanosome formation than did melanocytes of the benign simulants. However, the abnormalities were variable and were not limited to the SSMs. Our observations suggest that qualitative ultrastructural evaluation cannot be reliably used differentiating SSMs from benign melanocytic lesions.