33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

east carcinomas with overlapping features, this author always provides a histologic
grade for all invasive breast carcinomas (regardless of subtype) according to the
criteria adapted from those of Bloom and Richardson (3). Remember, occasional
cases of infiltrating lobular carcinoma contain considerable foamy, histiocytoid,
granular, and/or "lipid-rich" cytoplasm. The malignant cells resemble foamy
histiocytes, but they can be distinguished from that cell-type by their positive
cytokeratin immunostaining, concomitant lobular carcinoma in situ, and/or positive
mucicarmine staining. Also, some poorly differentiated carcinomas, especially from
the stomach, or medullary carcinoma from the thyroid, can metastasize to breast and
mimic primary invasive lobular carcinoma.
A benign lesion that can be over diagnosed as invasive lobular carcinoma is
lymphocytic lobulitis with prominent epithelioid fibroblasts (aka, “diabetic
mastopathy”). Taniere et al. (43) have reported two such cases. The patients presented
with rapidly enlarging masses wherein the prominent epithelioid fibroblasts were
misinterpreted as malignant cells of an invasive lobular carcinoma. Although initially
described in patients with longstanding insulin-dependent diabetes, more recent
reports have reported cases in patients with autoimmune disorders, such as SLE and
hypothyroidism.
LOBULAR CARCINOMA IN SITU
Background: Lobular carcinoma in situ (LCIS) is usually an incidental finding in
biopsies taken for other reasons, usually for fibrocystic changes (1,44-51). Although
most common in pre- and perimenopausal women, LCIS can also occur in postmenopausal
women. LCIS is a multicentric, bilateral lesion that has a well-established
association with the subsequent development of invasive carcinoma (44, 46,50), and
both breasts are at risk. (In a review article, Elston et al. [45] reported a 10- to 11-fold
increased risk for the subsequent development of invasive breast carcinoma with a
25% absolute risk in 10 years. But, it is very important to add that absolute risk is
highly dependent on patient age at the time of the initial diagnosis because the
incidence of invasive breast carcinoma varies considerably with age [46]).
The distinction of LCIS from atypical lobular hyperplasia (ALH) is quantitative since
individual cells of both lesions are essentially identical (48,50). Indeed, LCIS and
ALH have been collectively referred to as lobular neoplasia (48, 50). ALH has a
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