52-year-old female underwent excision of a breast tumor. Clinically a firm, not-movable, palpable mass had been noted.
- An irregular area of dense, fibrous tissue surrounded by adipose tissue is noted.
- The fibrous tissue is permeated by single file linear cords and sheets of tumor cells.
- Some tumor cells surround normal appearing acini or ducts in a concentric fashion (bull's eye appearance).
- Foci of acini distended by monomorphic, non-cohesive tumor cells are observed (LCIS).
- The monomorphic cells of the invasive carcinoma resemble those of the in situ component.
- Only few mitoses are detected.
- Of note is the diffuse growth pattern of this type of tumor. The tumor extends to the resection margin marked with black ink.
The presence of lobular carcinoma in situ (LCIS) / lobular neoplasia (LN) is a marker for an increased risk of developing breast cancer in either breast. Around one third of women with LCIS will develop an invasive carcinoma. Of these, about one third will be of the lobular type. Thus, LCIS may be a direct precursor of some carcinomas.
Invasive lobular carcinoma arises in the periphery within lobuli.