A subcutaneous nodule in a returning Chinese expatriate

Abstract

A 51-year-old Chinese man presented with a lump on his left buttock. Two years prior, he worked as a gold dredging contractor for one year in Banalia, Tshopo province, the Democratic Republic of the Congo, and received repeated unidentified insect bites. Three months prior, he found a bean-sized lump on his left buttock. He then developed an erythematous itchy rash on his legs that extended over his whole body, without fever or enlarged lymph nodes. The rash improved without treatment. The lump enlarged gradually over two months. On physical examination, the lump (diameter 2.5 cm) was not tender or movable. The patient was afebrile and did not have palpable inguinal lymphadenopathy. Laboratory data revealed normal neutrophils and eosinophils, C-reactive protein level, and erythrocyte sedimentation rate. Ultrasound revealed a low echogenic subcutaneous area (27 × 15 × 18 mm) and subcutaneous edema. Excisional biopsy and histopathological examination were performed (Fig 1). What is your diagnosis?