Clinicopathological features of metaplastic breast carcinoma

Metaplastic carcinoma of the breast (MpBC) is defined as a group of heterogeneous malignant neoplasms that contain glandular and non-glandular components with mixed epithelial and mesenchymal differentiations.

The aim of this study was to research the clinical and pathological characteristics of MpBC determining its rank among all breast cancers.

Metaplastic carcinoma of the breast was found in 7 out of 1,164 patients who had been diagnosed with breast cancer within the period of 12 years in our hospital. Demographic and clinical characteristics of the patients were retrieved from the patient files, and their final status was verified by a phone call. Diagnoses of the patients were confirmed by examining hematohylen and eosin (H&E) preparations. They were stained immunohistochemically for estrogen receptor (ER), progesterone receptor (PR), C-erbB-2, CK5/6 (Sitokeratin5/6), and EGFR (epidermal growth factor receptor), and the subgroups were determined according to the WHO classification.

All patients were female with a median age of 61 years (41-87 years). Three of them were diagnosed with stage IIB, 2 with IIIB and 1 with IV. Four patients had squamous type of metaplastic cell differentiation, 1 spindle, 1 adenosquamous, and 1 osteosarcomatous. In 6 out of 7 patients, ER, PR and C-erbB-2 expressions were negative immunohistochemically. In the case of squamous metaplasia, estrogen receptor was 10% and progesterone receptor was 5% positive. CK5/6 was positive in 5 cases. Epidermal growth factor was positive in all cases.

Metaplastic carcinoma of the breast is relatively rare and, in our series, its incidence was 0.6%. According to its immunohistochemical characteristics, MpBC can be interpreted as a subgroup of triplenegative breast cancers (TNBC). Five of the presented patients resembled the subgroup of TNBC with a basaloid phenotype. The chemotherapy regimens suggested in the treatment of MpBC are platin in the epithelial subgroup and high-dose anthracycline in the mesenchymal subgroup. There is a need of new studies that evaluate different choices of treatment as MpBC has a bad prognosis and an aggressive nature.