Acral Ulcerated Nodule in a Young Female

A young female in her mid-30s presented with a long-standing, minimally painful, and gradually enlarging red-pink growth on her right second toe which broke down into a non-healing ulcer from the past 4–5 months. On cutaneous examination, a solitary 1 × 1 cm ulcer was noted on the plantar aspect of the base of the right second toe. The ulcer floor was formed by pink granulation tissue surrounded by thick scaly collarette [Figure 1]. A 4-mm punch biopsy obtained from the center of the lesion revealed a tumor composed predominantly of elongated cells arranged in nests, lobules, and fascicles displaying high nucleus-cytoplasm ratio, prominent eosinophilic nucleoli, and mitotic figures. Intra- and intercellular melanin deposits were also noted focally [Figure 2]. Immunohistochemistry revealed positivity with S100 [Figure 3a] and HMB45 [Figure 3b].Figure 1: A 1 × 1 cm ulcer with thick scaly collarette on the plantar aspect of the base of the right second toeFigure 2: Photomicrograph showing elongated cells arranged in nests, lobules, and fascicles displaying high nucleus-cytoplasm ratio, prominent eosinophilic nucleoli, and mitotic figures along with focal intra- and intercellular melanin deposits [H and E, 10x]Figure 3: Immunohistochemistry at 10x showing positivity with S100 (a) and HMB45 (b)What is the diagnosis? Answer Spindle cell melanoma (SCM). Discussion Spindle cell melanoma is a rare subtype of melanoma that is characterized histologically by atypical spindle-shaped tumor cells. This variant of melanoma accounts for about 1–14% of all melanomas and predominantly affects the Caucasians beyond the 5th decade with a slight male preponderance. Clinically, the tumor has no specific morphology or site predilection. The lesions are often amelanotic and resemble any other benign or malignant lesions accounting for delayed diagnosis.[1,2] Histologically as well, SCM is difficult to differentiate from other benign and malignant spindle cell tumors.[3] The predominant histological features of SCM include elongated and atypical spindle cells accounting for more than 90% of the tumor. The cells are arranged in nests, lobules, and fascicles showing nuclear pleomorphism and high mitotic rate. Immunohistochemically, the cells stain positively with S100, HMB-45, Melan-A, SOX10, p75, laminin T, laminin NT, and c-KIT, and negatively with cytokeratins. The majority of the cells also show positivity with Ki-67, cyclin D1, and survivin. Desmoplastic melanoma (DM), another infrequent subtype of melanoma, also features spindle cells. While SCM features abundance of spindle cells, DM exhibits desmoplastic cells comprising more than 90% of the tumor. Immunohistochemistry is vital in differentiating SCM from DM. The latter exhibits positivity with collagen IV, CD68, MDM2, and trichrome, and the cells are negative for markers described above with SCM. The essential clinical, histological, and prognostic differences between SCM and DM are summarized in Table 1.[2,4]Table 1: Differences between spindle cell and desmoplastic melanomaAlthough acral lentiginous melanoma is commoner in darker skin phototypes, SCM presenting as acral amelanotic ulcero-nodular lesions is rarely reported.[5] Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.