Cystic [beta]2-microglobulin amyloidoma in a patient on long-term hemodialysis

We report a patient with β2 microglobulin amyloidosis (β2M) in whom cystic tumors were seen in the bilateral axillary region. The patient was a 68-year-old woman who had been on hemodialysis for more than 20 years because of IgA nephropathy. Computed tomography-guided biopsy was performed to confirm the diagnosis. Congo red staining, β2M immunohistochemistry, and electron microscopy examination of the biopsied sample showed extended β2M deposits in the cystic tumor. β2M-related amyloidosis in patients with long-term dialysis commonly presents as osteoarticular disease, although a soft-tissue pseudotumor, known as amyloidoma, has been reported. This is the first report in the English-language literature of amyloidosis presenting as bilateral axillary cystic tumors.