MALIGNANT MELANOMA, DESMOPLASTIC TYPE, CONTAINING PECULIAR NEUROID STRUCTURES
The radial growth component of this melanoma has a lentiginous component, as is usually the case with desmoplastic melanomas. Involvement of the entire thickness of the dermis at the time of the initial biopsy is, unfortunately, a feature that is also common in this melanoma variant. This particular example is either fibrogenic or it has remodeled the collagenous stroma of the reticular dermis. In addition to dispersed patterns and the formation of nondescript fascicles of tumor cells, this case has peculiar bundles of tumor cells that may represent fascicles cut in cross section. These vaguely remind me of structures that are sometimes seen in neuromas or in cellular neurothekeomas. The degree of cytologic atypia of the dermal component is minimal/moderate.

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From the nose of a 77 year old male:
 
Atypical lentiginous and junctional melanocytic hyperplasia (ALMH) as well as follicular involvement (FI) are prominent.

 
A low power view. Atypical lentiginous and junctional patterns are associated with striking modification of the character of the papillary and reticular dermis. The invasive tumor cells are spindle shaped in a dispersed pattern in this field.
A composite medium power view. There was involvement of the entire thickness of the biopsy. .
A high power view of a fascicle composed of spindle cells. Spindle cells cut in cross-section are in the lower left side of the picture.
A high power view showing pigment at the tips of the arrows. This was very sparse in this lesion. Melanin is unusual in the vertical growth component of most desmoplastic melanomas. Note the peculiar appearance of bundles of spindle cells cut in cross-section. You can also see bundles of this type in the composite medium power view. 

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