A CASE OF MUSCULAR HAMARTOMA OF THE BREAST

A 45-year-old woman presented with a left breast mass. The painless solitary tumor was palpated in the A region of the left breast. Ultrasonography revealed an internally isoechoic mass with a regular margin. Mammography visualized a light spherous tumor with a smooth margin. Histopathologically, the excised specimen was 1.5×1.2cm in size and the section was milk-white in hue and hard. At low magnification, the tumor was relatively illdefined and localized but with no capsule. Mild compression of surrounding glandular ducts was also observed. At high magnification, smooth muscle fascicular or nerve fascicular structures were seen surrounding the ducts and framework. A biphasic pattern was clear in the duct itself and neither a cytological heterotype nucleus nor mytosis was seen in the duct and surrounding cells. Muscle-actin and α-smooth muscle actin staining showed strong positive responses in the cyto-plasms of tumor cells in the vicinity of the duct. These findings confirmed that this localized tumor, growing mainly in smooth muscle cells, was a muscular hamartoma.