Fibrous Tumor of the Breast: Case Report of an Underrecognized Entity

Fibrous tumor of the breast is an underappreciated, distinctive, benign, nonrecurrent lesion of the breast. The cytological features of this condition are not well characterized. We present a case report of a 30-year-old female presenting with a hard mass in her right breast. Fine needle aspiration showed smears of low cellularity showing a few clusters and sheets of mostly uniform benign epithelial cells, some of which were lined by myoepithelial cells. Scattered bipolar bare nuclei or stromal fragments were not seen. Excision with subsequent histopathological examination revealed a well-circumscribed, heavily collagenous tumor with atrophy and replacement of the epithelial and ductal elements of the breast, and diagnosed as fibrous tumor. Being nonrecurrent, it is important to distinguish this lesion from fibromatosis of the breast. 1. Introduction Fibrous tumor of the breast is a distinct disease entity characterized by a discrete breast mass composed of collagenized breast stroma along with hypoplasia of ductal and epithelial elements. This condition is comparatively rare and underrecognized. We present a case of fibrous tumor of the breast with the fine needle and histopathological features and discuss its clinical significance and differential diagnosis. 2. Case Report A 30-year-old female presented with a mass on the upper outer quadrant of the right breast with a hard mass measuring 6？cm in diameter. Fine needle aspiration revealed smears of scant cellularity showing sheets of benign epithelial cells with some cells showing mild atypia. There was no stromal component, nor were there any benign bipolar cells in the background (Figures 1 and 2). Figure 1: Smears prepared from fine needle aspirates show occasional sheets of benign ductal epithelial cells (Pap, ×400). Figure 2: Giemsa-stained smear prepared from fine needle aspirate shows sheet of benign ductal cells with lining myoepithelial cells. Excision showed a well-circumscribed mass measuring 5？cm in diameter, with a solid, fibrous cut surface, and calcific specks (Figure 3). Figure 3: Excised specimen showing well-circumscribed tumor with solid fibrous cut surface and some calcific specks. The superficial cut along the center was made in the surgery to have a closer look. Histologically, the tumor comprised of predominantly densely collagenized stroma, with atrophic ductal and epithelial elements (Figures 4(a) and 4(b)). There was absence of vascular or pseudovascular spaces, nerves, or any lymphocytic infiltrate. Based on these features, a diagnosis of fibrous tumor of the breast was