Case 18 Male, 23 years. Skin lesion of scalpShow diagnosis & comments
Small cell naevoid melanoma
Small cell naevoid melanomas are sometimes underdiagnosed because of the small, naevoid cell type and the sometimes regular overall (verrucous or dome-shaped) appearance. Some are bulky, esepcially the ones arising in large congenital naevi, they display considerable mitotic activity and there may be subtle but abrupt variations in cellular features or lesional architecture. Ascent may or may not be present. These melanomas sometimes affect children; such childhood lesions appear to be most common on the scalp.
Note the deeptly intented, convoluted and grooved small nuclei and areas of this melanoma (see last micrograph of the panel below). It differs from the larger van vesicular, or dark and lymphocyte-like, or elongated nuclei seen in the large majority of melanocytic naevi. Although I have not studied this systematically and am not aware of any study on this in the literature, it is my impression that this nuclear type is quite common in small cell naevoid melanomas. If one sees such nuclei, I believe it is wise to think twice (i.e., do levels, hunt for other possible subtle indicators of malignancy, ask for help) before rendering a diagnosis of naevus.
- Magro CM, Crowson AN, Mihm MC. Unusual variants of malignant melanoma. Mod Pathol. 2006 Feb;19 Suppl 2:S41-70.
- Barnhill RL. Childhood melanoma. Semin Diagn Pathol. 1998 Aug;15(3):189-94.