Applied Radiology

PROBLEM:

A 40-year-old woman pre-sents for evaluation of a palpable mass at the 3 o'clock position of the left breast (figures 1-4). What is your diagnosis?

ANSWER:

Medullary carcinoma

DISCUSSION:

Medullary carcinoma is a subtype of infiltrating ductal carcinoma, accounting for 5% to 7% of all breast cancer. It is characterized by its well-circumscribed borders, sheets of poorly differentiated cells with high nuclear grade, and prominent lymphoid infiltration both in and around the tumor. Up to 60% of patients with medullary carcincoma are under 50 years old and it represents 11% of breast cancers in women 35 years of age or younger. ¹ The prognosis is more favorable than with other ductal carcinomas, with reports of 10-year survival rates as high as 92%. ²

Mammographically, medullary carcinoma typically appears as a well-circumscribed, medium to high density, non-calcified mass with lobulated contours. Occassionally, there is a partial or complete "halo sign" of surrounding lucency. ³ Reactive axillary adenopathy even without nodal metastasis is a distinguishing feature. ⁴

On gross pathology, there is typically a distinct margin between the tumor and the surrounding breast tissue and, if there is significant peripheral fibrosis, the appearance is that of an encapsulated lesion. The borders "push" rather than infiltrate the surrounding tissue. On microscopic pathology, sheets of solid syncytium like large cells with pleomorphic nuclei and mitosis are surrounded by a lymphoplasmacytic reaction which results in the smooth, rounded contour seen on mammography. ¹ There is a lack of tubule formation. The diagnostic work up of such a palpable mass should include ultrasound examination to exclude a cyst. If a solid mass is noted, ultrasound-guided core needle biopsy is appropriate to allow definitive management. Based on mammographic features, other diagnostic considerations include both benign and malignant lesions. The presence of adjacent and coalescing nodules favors malignant etiology in this case. Intracystic papillary carcinoma and mucinous (colloid) carcinoma also often present as relatively well-defined, dense masses. Among benign lesions, a fibroadenoma or phyllodes tumor would be the most likely considerations. Although this process was mammographically dense, complex cysts or papillomas could also have this appearance.

Prepared by Barbara M. Jaeger, MD, and Wendie A. Berg, MD, PhD, Department of Radiology, University of Maryland School of Medicine, Baltimore, MD.