Deep Dermal and Subcutaneous Deposits in Thin Melanoma: A Cautionary Tale

Melanoma microsatellites are peritumoral metastatic deposits and surrogates for potentially aggressive biological behavior. Their presence indicates clinical stage III disease. They are rarely reported in association with thin primary tumors (< 1.0 mm, pT1). As a poor prognostic factor, the identification of microsatellitosis in an otherwise localized, thin primary melanoma would result in upstaging and additional investigative and therapeutic considerations. Therefore, when microsatellitosis is suspected, efforts should be made to exclude possible mimics. We present three cases of thin melanomas with deep dermal/subcutaneous deposits to highlight the importance of careful and thorough gross and microscopic examination of all melanoma cases, regardless of T-category.