Pure and Mixed Variants of Desmoplastic Melanoma: A Single-Center, Retrospective, Clinicopathologic Review

Abstract

BACKGROUND Desmoplastic melanoma (DM) is a rare melanoma variant. Prognostic indicators and survival vary widely and are further confounded by the histopathologic distinction between pure DM (pDM) and mixed DM (mDM) subtypes. The utility of current treatment guidelines is limited by the lack of evidence-based recommendations. OBJECTIVE To compare the clinicopathologic characteristics of pure and mixed subtypes of DMs. METHODS All cases of DM were identified from the Washington University in St Louis institutional pathology database between January 2000 and September 2022. Fifty-two cases were identified and subsequently categorized as pure (n = 26) or mixed (n = 26). Clinical and histopathologic data were collected and compared. RESULTS There were no differences in demographics or tumor location between pure and mixed subtypes. Patients with mDM were more likely to have mitoses present (p = .03). There were no differences in Breslow depth, tumor diameter, level of invasion, ulceration, and lymphovascular or perineural invasion. The utilization of sentinel lymph node biopsy (p = .17) and sentinel lymph node positivity (p = .67) were also similar. CONCLUSION Despite histopathologic distinction between pDM and mDM, these subtypes were found to have similar clinicopathologic characteristics, including similar rates of sentinel lymph node metastasis.