What are the histologic findings of mucinous carcinoma breast cancer?

Updated: Feb 04, 2021
  • Author: Pavani Chalasani, MD, MPH; Chief Editor: John V Kiluk, MD, FACS  more...
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Mucinous (colloid) carcinoma is another rare histologic type, seen in fewer than 5% of invasive breast cancer cases. It usually presents during the seventh decade of life as a palpable mass or appears mammographically as a poorly defined tumor with rare calcifications.

Mucin production is the histologic hallmark. There are 2 main types of lesions, A and B, with AB lesions possessing features of both. Type A mucinous carcinoma represents the classic variety, with larger quantities of extracellular mucin (see the image below), whereas type B is a distinct variant with endocrine differentiation.

Breast cancer. Colloid (mucinous) carcinoma. Nests Breast cancer. Colloid (mucinous) carcinoma. Nests of tumor cells in pool of extracellular mucin.

DCIS is not a frequent occurrence in this setting, though it may be found. Most cases are ER- and PR-positive, but HER2 overexpression is rare. Additionally, these carcinomas predominantly express glycoproteins MUC2 and MUC6.

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