Purpose: 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.
Methods: 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.
Results: 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.
Conclusion: 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.