546 - GIANT CELL TUMOR OF THE BREAST WITH PULMONARY METASTASIS: A CASE REPORT

Abstract

Giant cell tumor of soft tissue (GCT-ST) is an extremely uncommon tumor that resembles GCT of the bone in morphology
and immunohistochemistry, usually occurs in the superficial and deep STs of the extremities, and the breast is a very rare
location. It is composed of a mixture of round mononuclear cells and multinucleated osteoclast giant cells. It is classified as
an intermediate-type fibrous tissue cell tumor, occasionally metastatic type, that has a benign clinical course when treated
adequately by complete excision. Therefore, local recurrence or distant metastasis is extremely rare. A 36-year-old female
patient was admitted to the Mastology Service with a 20-cm palpable nodule in the left breast, associated with ectasia
without signs of lymphadenopathy; reports hypertension, hypothyroidism, and hysterectomy in 2006, due to uterine myomatosis. In relation to family history, her father had prostate cancer. On imaging examinations, a breast ultrasound was
performed and showed a solid and hypoechoic node, lobulated contour with small cystic areas inside, with post acoustic
phenomenon, located in the superolateral quadrant of the left breast. Mammography confirmed BIRADS 0. The biopsy
revealed an atypical epithelial lesion with abundant osteoclast-like giant stromal cells. Computed tomography of the chest
revealed nonspecific pulmonary nodules in the right upper lobe, the largest measuring 0.5 cm. Immunohistochemistry
concluded histiocystic neoplasm rich in multinucleated giant cells — Ki-67 15%, AE1/AE3, and GATA-3 negative, CD68
positive. As clinical management, a simple left mastectomy was indicated. Anatomopathology showed a fibrohistiocytic
neoplasm with abundant osteoclast-like multinucleated giant cells, measuring 10.5 cm.