A Case of Systemic Amyloidosis Diagnosed After Excision of a Cutaneous Tumour of the Buttocks

Abstract

A 72‐year‐old Japanese man was referred to our hospital with two tumours on the buttocks. Two solitary, 2.5 × 1.5 cm‐sized, dark brown, well‐demarcated elevated plaques were observed, one on each side of the gluteal cleft, and dermoscopic examination showed comedo‐like openings, multiple milia‐like cysts, and a cerebriform pattern with fissures and ridges. Seborrhoeic keratosis was suspected, and surgical excision was performed because the patient experienced pain while sitting. However, histopathology was positive for Congo red stain and direct fast scarlet stain. Further examination led to the diagnosis of systemic amyloidosis. Amyloid deposition is occasionally observed in specimens obtained from the excision of a cutaneous tumour. When such amyloid deposition is identified, systemic amyloidosis, localised amyloidosis, and secondary amyloidosis should be considered in the differential diagnosis. Because systemic amyloidosis has a poor prognosis, early treatment is essential. A case of systemic amyloidosis that was diagnosed and treated following the incidental detection of amyloid deposition in tumours of the gluteal cleft is presented.