Metaplastic carcinoma of the breast: clinicopathological features and immunohistochemical analysis

Metaplastic breast carcinoma (MBC) is a rare and heterogeneous group of neoplasms characterized by a mixture of spindle, squamous and/or mesenchymal cells. The purpose of this study was to assess the immunohistochemical features, biological characteristics and myoepithelial differentiation of a series of MBC patients.

The archival pathological material from 33 MBC patients was evaluated. Analysed were patient characteristics, pathological and immunohistochemical features and their relevance as prognostic factors of patient survival.

The median patient age was 44 years (range 17-82), and the median tumor size 5 cm (range 0.5-17.0). The majority of patients (n=29; 87.8%) were treated by modified radical mastectomy, 1 (3%) patient had breast-conserving surgery and another 1 (3%) had latissimus dorsi flap reconstruction. Metastasis to axillary lymph nodes was found in 14 (42.4%) patients, 18 (54.5%) patients were triple negative, and 22 (66.7%) were epidermal growth factor receptor (EGFR) positive. The 5-year event-free survival was 25.9%, whereas the 5-year overall survival was 27.5%. Immunohistochemical analysis showed the following: vimentin positivity in 31 (93.9%) patients, high molecular weight cytokeratin (HMWCK) positivity in 31 (93.9%), CK 5/6 positivity in 28 (84.8%), P 63 positivity in 19 (57.6%) and calponin positivity in 18 (54.5%) patients. Two particularly interesting findings were noted, namely, myoepithelial differentiation in the carcinomatous and sarcomatous elements of MBC, and EGFR immunopositivity.

Immunohistochemistry has an important role to play in the diagnosis and treatment decision of MBC. This report presents findings related to a broad panel of immunohistochemical markers for a large series of metaplastic cases, which indicate poor prognosis for this tumor.