Metaplastic
carcinoma of the breast shows squamous, sarcomatous, or chondromatous differentiation and has a poor prognosis.
Laminin 5 is a heterotrimer of alpha3, beta3, and gamma(2) [corrected] chains and induces aggressive properties in
cancer cells including motility, invasion, and epithelial to mesenchymal transition. Twenty-five cases included 7 squamous, 4 sarcomatous, 8 chondroid, 1 fibromatosislike metaplastic
carcinomas, and 5 cases with 2 metaplastic components.
Tumors were stained with
laminin 5-specific beta3 and gamma(2) [corrected] chain, p63, and
cytokeratin 5/6 (CK 5/6)
antibodies. All 4
antibodies stained normal myoepithelium. Both
laminin 5 antibodies stained 24/25 (96%) of the
tumors, with an identical distribution of the 2 chains in 87.5% of the positively staining cases. In contrast, p63 and CK 5/6 stained 68% and 64% of the
tumors, respectively. By comparison, only 16% of high-grade
carcinoma controls stained for
laminin 5. Similar to the metaplastic
carcinomas, all 12 triple negative
tumors, those negative for
estrogen receptor,
progesterone receptor, and Her2/neu, expressed
laminin 5. None of 4 breast
sarcomas stained for either of the
laminin 5 chains or CK 5/6, but 1 (25%) stained for p63.
Laminin 5 expression in metaplastic and other basal-like
carcinomas is of interest for several reasons. First, these data provide additional evidence of the myoepithelial and basal-like phenotype of these
carcinomas. Second, these are the only
breast carcinoma subtypes to demonstrate
laminin 5 staining in a large proportion of cases. Third, expression of
laminin 5 in metaplastic
carcinomas may suggest a mechanism for their increased aggressiveness and epithelial to mesenchymal transition phenotype. Finally, compared with other myoepithelial markers,
laminin 5 is more sensitive than those previously published. Thus
laminin 5 may be helpful for making the diagnosis of metaplastic
carcinomas in biopsies, allowing the potential for aggressive early treatment. Further study of other basal-like
tumors for
laminin 5 expression is warranted to determine the usefulness of
laminin 5 in their diagnosis.