Track

Case Reports

Abstract

Desmoplastic melanoma (DMM) is an uncommon melanoma variant that is often difficult to recognize both clinically and histopathologically. Delays in diagnosis can occur from nonspecific clinical presentations, particularly in the absence of significant pigmentation. Similarly, histopathologic findings are frequently subtle and misinterpreted as benign. We report a 64-year-old female with a history of obesity, diabetes mellitus, and chronic wounds now diagnosed with DMM in the setting of an enlarging wound. The patient experienced a significant foot trauma in childhood, resulting in a longstanding history of chronic wounds of her affected extremity. More recently, she developed an ulcerated, non-pigmented foot lesion near this site of trauma with similar lesions noted on the knee and shin. Prior biopsy was diagnosed as dermatofibroma. Despite debridement and antibiotics, she developed new nodules resulting in repeat biopsies.  Both specimens demonstrated atypical spindle cells in the dermis and subcutis with collagen entrapment, scattered mitoses, and absence of epidermal involvement. Immunohistochemistry highlighted neoplastic cells were SOX10+ P63- CK5/6- CD34- and desmin-. The overall findings were consistent with DMM, favoring a metastatic melanoma lesion. Subsequent imaging demonstrated widespread metastatic disease.  In this case, nonspecific clinicopathologic findings perpetuated a benign diagnosis, with malignancy recognized only after marked disease progression. A lack of therapeutic response, as shown here, should prompt critical reevaluation of diagnosis. This review will discuss clinical and histologic mimics of DMM through the context of this unfortunate case and review immunophenotypic findings to raise awareness of diagnostic pitfalls in this rare but clinically significant melanoma.