Contributed by Terri E. Jones, MD and Jing Yu, MD, PhD
The patient is a female in her 50's who presents for a routine mammography. A density is identified at the 10:00 position in the left breast on craniocaudal (LCC) and mediolateral (LML) views (Figure 1). To further examine this lesion, diagnostic mammography, left breast ultrasound, and a left axillary ultrasound are performed. The ultrasound of the left breast demonstrates an irregular, hypoechoic nodule in the 10:00 region, 2 cm deep to the nipple and measuring 1.8 x 1.3 x 1.1 cm (Figure 2). The diagnostic mammography recapitulates these findings. The left axillary ultrasound shows normal appearing lymph nodes. The nodule is classified as indeterminate by the radiologist and ultrasound-guided biopsy of the lesion is recommended. This was consistent with a BI-RADS category of 4A, denoting a suspicious abnormality. The patient underwent an ultrasound guided biopsy with clip placement at the biopsy site.
The results of the biopsy showed a sclerotic papillary lesion, florid adenosis, ductal epithelial hyperplasia, fibrocystic changes, necrosis, and calcifications. It was recommended that she pursue surgical excision of the lesion. She subsequently underwent ultrasound-guided radioactive seed placement and radioactive seed localized excisional biopsy of the left breast lesion.
Gross examination revealed a 2.8 x 2.1 x 1.6 cm tan red nodular and papillary mass with central cyst formation.
The tumor showed two distinct morphologies (Figure 3): (1) a circumscribed biphasic malignant tumor with significant cytologic atypia in both glandular and myoepithelial components, foci of necrosis, and up to 12 mitoses per 10 high power fields; (2) foci of invasive tumor nests along the border of the central mass, the largest up to 0.7 cm.
Immunohistochemically, these morphologies were also characteristic (Figure 4). The large tumor showed CK7 positivity in the epithelial component (A), with positivity of p63 in the myoepithelial component (B), whereas the invasive tumor cells showed positivity for p63, CK5, CK7 and S-100 (C, scattered). Myosin heavy chain was negative around the invasive tumor nests (D).