The invasive component of this type of melanoma can resemble a variety of benign and malignant spindle cell tumors of skin. The diagnosis frequently depends on demonstrating the radial growth phase of a melanoma, and this is usually lentiginous. If the radial growth phase of the melanoma is not demonstrated, as is often the case with small biopsies, the diagnosis may depend on a high degree of suspicion by the pathologist that is confirmed by appropriate immunoperoxidase studies. An S-100 study is often necessary to distinguish between tumor and early scar in margins of resection. This type of melanoma has usually invaded into the deep reticular dermis or into the subcutis by the time the biopsy is taken.
Neurotropism is sometimes present.
This type of melanoma truly requires wide margins of resection. Scan of a tumor from a sun exposed area from an elderly patient. Low power of the dermal component. Low power of a superficial part of the tumor. Low power of another superficial area.