Medullary Carcinoma of the Breast

Definition

A rare breast carcinoma with a syncitial growth pattern and high grade cytology reported to have a good prognosis

Syncitial growth pattern in at least 75% of tumor
- Cell margins not distinct
Heavy mononuclear inflammatory infiltrate
Microscopically circumscribed
- No infiltration
Absence of neoplastic ducts or glands
High grade pleomorphic nuclei with prominent nucleoli
We require all five features to make the diagnosis
- Carcinomas lacking one of these features have been termed "atypical medullary carcinoma" by some
- We do not use that term, diagnosing them instead as infiltrating ductal carcinoma

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342