Case report of superficial acral fibromyxoma

Abstract

<h3>Case presentation</h3> A 38-year-old female presented with a soft tissue lesion beneath the nail bed of the right middle finger. Imaging showed a lucent lesion involving the medial aspect of the shaft of distal phalanx with some bone erosion. Macroscopic examination showed a 12mm transparent myxoid nodule. Microscopically there was a uniformly moderately cellular myxoid lesion with a pushing margin, composed of spindled and stellate cells. No cytological atypia, mitosis or necrosis was observed. Thin-walled, curvilinear blood vessels and scattered mast cells were also present throughout. Immunohistochemistry was negative for NF, S100, EMA and SMA, and positive for CD34. Fluorescence <i>in situ</i> hybridisation (FISH) was negative for FUS translocation, specific for low-grade fibromyxoid sarcoma. <h3>Diagnosis</h3> Superficial acral fibromyxoma. <h3>Discussion</h3> These lesions are typically located in the dermis or subcutis of fingers and toes, with a tendency to involve the nail bed. They are composed of spindled and stellate cells in a myxoid background with accentuated vasculartiy and increased mast cells. They are typically CD34, EMA and CD99 positive and need to be differentiated from low-grade fibromyxoid sarcoma (MUC4–, CD34–, FISH showing FUS translocation), myxoid neurofibroma (S100+), superficial angiomyxoma (CD34–) and myxoid DFSP [also CD34+ but has subcutaneous fat infiltration and typically shows t(17;22)]. <h3>Prognosis</h3> Generally benign with 10% recurrence rate and therefore needing complete excision and follow-up.