Abstract

Malignant melanoma has a variety of clinical and histopathologic appearances and can uncommonly mimic inflammatory diseases. We report an unusual case of superficial spreading melanoma presenting as an eczematous plaque. The patient was a 67-year-old man with a 7cm scaly pink plaque on his left elbow which had been previously diagnosed as nummular eczema; it was treated for nearly 10 years with escalating topical corticosteroids and noted response to therapy. However, it continued to grow and developed gross grey-purple globules and erosions. Biopsy was performed and histopathology demonstrated superficial spreading melanoma with Breslow depth of ≥0.6cm. Re-excision revealed Breslow depth of 1.6mm with ulceration and 4 mitotic figures/mm². The patient underwent wide local excision with negative sentinel lymph node biopsy from 3 nodes in the left upper epitrochlear and left axillary regions. CT chest/abdomen/pelvis was negative for metastatic disease or lymphadenopathy. The final melanoma staging was IIA (pathologic staging pT2b N0 M0). Amelanotic melanoma has been rarely reported in the literature presenting as an eczematous plaque, periorbital dermatitis, contact dermatitis, tinea corporis, intertrigo, orbital cellulitis, verruca, and onychomycosis. Scale is relatively common in non-nodular amelanotic melanomas and is hypothesized to be caused by induction of keratinocyte differentiation by neoplastic melanocytes. Our case is unique in the long-standing nature of this lesion and prior response to topical therapy, which raises the possibility of melanoma arising at the site of an inflammatory disorder, although the similar presentation supports a long-standing melanoma. These findings serve to enhance understanding and recognition of uncommon melanoma presentations.