Case Number : Case 2144 - 28 August 2018 Posted By: Uma Sundram

 ? Merkel cell carcinoma with epidermotropic component 

IHC needed

To me this lesion is very difficult to interpret. My differential diagnosis includes a clonal nevus or an invasive melanoma. The worrisome part is that the lack of maturation is not just limited to one area, it's throughout the lesion. There are also other structure disorders such as asymmetry, large irregular junctional nests and coalescing of the junctional nests. But part of the challenge is the patient's young age, which is unusual for a melanoma. Overall I favor an invasive melanoma.

Nevoid lymphoma.

Favor melanoma too

Melanoma, arising in a nevus. While the patient's young age is a challenging feature, it's the only unusual thing about this lesion. The lesion itself is quite concerning; it's broad, asymmetric, has a focal sheet like dermal proliferation, has large dermal nests within the lower aspects of the lesion, and has deep pigment. The junctional component is confluent as well. Overall a concerning lesion, and should be treated as a melanoma, even if the trigger isn't pulled. Nevoid melanoma is a good thought. S100 and MART1 are positive.