Primary dermal melanoma: clinical behaviour, prognosis and treatment

Abstract

PurposePrimary dermal melanoma (PDM) is a subtype of cutaneous melanoma, confined to the dermis, which poses a challenging clinical dilemma. It may represent a true primary melanoma or a dermal cutaneous metastasis. This study aimed to delineate the histopathological characteristics and prognosis of PDM in a large patient cohort to guide appropriate treatment strategies. MethodsA search of the Melanoma Research Database at Melanoma Institute Australia was conducted to identify all possible PDM patients at our institution diagnosed from 1978 to 2013. Overall, melanoma-specific and disease-free survival outcomes of the PDM group were compared to those of similar cohorts of Stage I-II and Stage IV M1a melanoma patients based on propensity score matching. ResultsSixty-two PDM patients were identified from the MRD with a median follow-up of 6.3 years. Five-year survival was 87.1% and overall survival was 74.2%. PDMs had a significantly improved overall survival (p = 0.0002) and melanoma-specific survival (p = 0.001) compared to Stage I-II controls, however there was no difference in disease-free survival (p = 0.08). PDMs also demonstrated improved overall survival (p < 0.0001), melanoma-specific survival (p < 0.0001) and disease-free survival (p < 0.0001) compared to Stage IV M1a controls. ConclusionThese findings demonstrate that PDMs have a more favorable prognosis compared to stage I-II cutaneous melanomas and suggest that these are in fact true primary lesions. This study thus provides evidence to justify a treatment approach, by way of a wide local excision and possibly sentinel lymph node biopsy, as for early stage primary cutaneous melanomas.