Amyloid tumor of the breast

BACKGROUND: Amyloid tumor of the breast is a rare disease, which was first reported in 1973. To date, only six cases have been reported in Japan. CASE PRESENTATION: A 45-year-old woman who had a medical history of Sjogren’s syndrome presented with a lump of 3 cm in diameter on the outer side of the right breast. Mammography showed no abnormality. Ultrasonography showed a well-defined and rough hypoechoic mass of 32 mm in diameter at the site of the lump. With suspicion of breast cancer, an ultrasound-guided vacuum-assisted breast biopsy was performed. For pathological diagnosis, hematoxylin and eosin staining showed deposits of nonstructural substances in the interstitium. The specimen stained red with Congo red staining and showed green birefringence under a polarizing microscope. Thus, the mass was diagnosed as an amyloid tumor. Since the patient had Sjogren’s syndrome, it was considered a breast finding of autoimmune disease. We considered further therapy to be unnecessary, and annual follow-up was recommended. CONCLUSIONS: We diagnosed the mass as an amyloid tumor by an ultrasound-guided vacuum-assisted breast biopsy without resection. The patient had no systemic symptoms suspected systemic amyloidosis, and we diagnosed localized amyloidosis. An amyloid tumor of the breast may show findings suggestive of breast cancer. Pathological diagnosis before surgery is important to avoid excessive invasion. If deposits of nonstructural substances are observed by hematoxylin and eosin staining, Congo red staining should be added.