Mixed Versus Pure Variants of Desmoplastic Melanoma: The Cleveland Clinic Experience.

BACKGROUND: Desmoplastic melanoma (DM) is a subvariant of spindle cell melanoma, accounting for less than 4% of all cutaneous melanomas. It occurs later in life and is associated with chronic sun exposure. Desmoplastic melanoma prognosis is considered more favorable than other variants, with lower rates of metastasis and higher survival. Recently, DM has been further subclassified into pure and mixed, calling into question surgical management and patient outcomes as well as viability of current nationwide databases without this distinction.
METHODS: We identified all patients with a histopathologic diagnosis of DM from the Cleveland Clinic electronic melanoma database (n = 58) from 1997 to 2013. Clinical and histopathologic data were collected. Comparison in clinical variables was performed between patients who had pure (n = 15) and mixed (n = 43) variants of DM.
RESULTS: There were no differences in age, sex, location of lesion, Breslow depth, ulceration, or regression. Patients with mixed DM were more likely to have lymphovascular invasion (P = 0.03) compared with pure DM. There was no difference in performance of sentinel lymph node biopsy (P = 0.25) or sentinel lymph node positivity (P = 0.31) between the 2 groups. Recurrence was present in 13.3% of pure and 30.2% of mixed patients. Overall, Kaplan-Meier 3-year survival was 75% for pure and 80% for mixed DM (P = 0.53).
CONCLUSIONS: Pure and mixed DMs seem to have similar clinical characteristics and outcomes. This indicates that analysis of national datasets without this subclassification remains viable.