Skin-Colored Nodule on the Scalp of a Middle-aged Man

Abstract

An otherwise healthy man in his 40s presented with a 3-month history of an asymptomatic nodule on his scalp. There were no systemic complaints, history of arthropod bite, immunosuppression, travel abroad, or contact with animals in the recent past. Physical examination revealed a skin-colored, firm, nontender, freely mobile 2 × 1.5-cm nodule with overlying normal skin on the right occipital region of the scalp (Figure , A). There was no lymphadenopathy. No other cutaneous lesions were present.The nodule was completely excised and sent for histopathologic examination, which revealed a nodule in the dermis with an unremarkable epidermis. Cross-sections of parasites were present, surrounded by a fibrous capsule (Figure , B). The parasite showed an outer cuticle, muscle layer underneath, and gravid uterus filled with microfilariae (Figure , C). The cuticle demonstrated a wavy pattern of longitudinal ridges on its outer surface (Figure , D). The fibrous capsule contained mixed inflammatory infiltrate of lymphocytes, eosinophils, histiocytes, and plasma cells. Findings of slitlamp examination and fundoscopy of the eyes were normal. Findings of routine hematologic and biochemical investigations were normal. No microfilaria was seen in peripheral blood. Findings of chest radiography and abdomen ultrasonography were unremarkable.