MALIGNANT MELANOMA,  MINIMAL DEVIATION VARIANT OF DESMOPLASTIC
MELANOMA VERSUS LENTIGO MALIGNA WITH AN INCIDENTAL NEUROFIBROMA
Atypical lentiginous melanocytic hyperplasia characteristic of lentigo maligna is associated with a dermal spindle cell tumor that looks like a neurofibroma. A few isolated atypical cells are seen in the deep part of the lesion, and one of these is perineural. The intraepidermal component of this lesion has a spindle cell component that resembles some of the superficial dermal spindle cells. A few of the superficial spindle cells contain melanin. Based upon these findings, a diagnosis of minimal deviation desmoplastic melanoma arising in a lentigo maligna would be justified. The conceptual basis for such a diagnosis has been provided by Reed. This would follow the dictum that any nevoid or spindle cell tumor in the dermis that  deviates from ordinary nevus or  classical spindle cell tumor such as a neurofibroma should be viewed as melanoma if there is evidence of the radial growth phase of a melanoma.

A diagnosis of melanoma was prudent in this case, but one cannot be absolutely certain that this was not an overcall. .
Scan  of biopsy. Click on the image to get a large composite picture (takes a while to download).

 
High power view of a representative part of the epidermis. Atypical lentiginous melanocytic hyperplasia characteristic of lentigo maligna is present.
High power view of another part of the epidermis showing spindle cells in the lower epidermis and in the dermis. In addition to pigmented macrophages, pigment is seen in a few of the dermal spindle cells.
High power view of the spindle cell tumor in the dermis. If the picture doesn't convey it, it looks a lot like a neurofibroma.
High power view of the deepest part of the dermis involved by tumor. Arrows point to atypical cells. The one at the left side of the picture is perineural.

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