Genital β2-Microglobulin Amyloidoma in a Long-Term Dialysis Patient

We present the case of a 58-year-old Japanese woman with a huge amyloid tumor in the genital region. Hemodialysis therapy was started for renal failure secondary to polycystic kidney disease in 1974. From 1989 to 1991, carpal tunnel decompression was performed surgically, and β2-microglobulin (β2MG)-amyloid deposition was found in the wrists. She was hospitalized at our institute for evaluation of lower-abdominal fullness and lower-extremity edema in March 2003. Magnetic resonance imaging showed a huge mass measuring 9.0 × 6.0 × 5.0 cm sandwiched between the vagina and rectum. The mass was hypointense compared with adjacent muscle on T2-weighted images. Computed tomography showed soft-tissue density accompanied by diffuse calcification. A biopsy specimen of the mass obtained by using a transvaginal approach showed material that was positive for β2MG-amyloid immunohistologically. When patients on long-term dialysis therapy develop a genital mass with low-signal intensity on T2-weighted images by magnetic resonance imaging and diffuse calcification by computed tomography, β2MG-amyloidoma should be considered as a differential diagnosis.