Matrix-Producing Breast Carcinoma with MyoepithelialDifferentiation – Description of 11 Cases and Review ofLiterature Aimed at Histogenesis and Differential Diagnosis

Overview

Objective:
Presentation of variable morphology of the so-called matrix-producing carcinoma, therare variant of metaplastic breast carcinoma. Establish the extent of myoepithelial phenotype byimmunohistochemistry and assess behaviour of the lesion.Design: Review of clinicopathologic data of 11 cases.Setting: Private Biopsy Lab s.r.o., Pilsen and Šikl’s Department of Pathology, Charles Universityand Faculty Hospital, Pilsen.Methods: Included are eleven cases from Breast Registry, Biopsy Lab s.r.o., Pilsen and PathologyDepartment, Faculty Hospital in Hradec Králové and Martin and from Biopsy Lab in Hořovice.Analyzed were morphology, stage, grade and follow up. Myoepithelial phenotype was demonstratedimmunohistochemically by LSAB+ system (DAKO) and seven conventional myoepithelialmarkers (GFAP, aktin S, calponin, cytokeratin 14, p63, CD10 and P-cadherin) were used. Oncogenep53 and Her2/neu were also detected.Results: Matrix-producing carcinoma is an extremely rare type of metaplastic carcinoma of thebreast, where high-grade epithelial component continually merges with heterologous mesenchymalchondroid component without overt spindle cell sarcomatoid pattern in between. There were allwomen at the age of 32 to 86-years (average 54 years, median 52 years) and the maximum tumor diameterranged from 18 to 60 mm (average 32 mm). The axillary LN was positive in six cases in the timeof diagnosis. The follow up available in 9 women ranged from three months to ten years (average 24months); dissemination of the disease was observed in three cases; 2 of these patients died of diseaseafter three and ten years, respectively. The heterologous mesenchymal chondroid component wasproduced in two different ways; one displayed typical structure of low-grade hyaline cartilage, in thesecond one the epithelial tumorous cells were embedded in the homogenous eosinophilic extracellularmatrix giving appearance of chondroid aura. Metaplastic component constituted 5-75% of thetumor volume. Immunohistochemical evidence of myoepithelial differentiation in all neoplasms wasdemonstrated, with at least two conventional myoepithelial markers (actin S, calponin, GFAP, CK14,CD10, p63 and P-cadherin) being positive in every case. Expression of p53 was identifi ed in six cases,all tumors were Her2/neu negative. Histologically the metastases were formed either by carcinomacells only, or more frequently, they replicated the structure of primary lesion.Conclusion: As a rare entity, matrix-producing carcinoma of breast displaying myoepithelialphenotype, deserves separate position in tumor classifi cation. It differs from conventional myoepithelialcarcinoma and from heterologous metaplastic carcinoma, where the matrix emanatefrom undifferentiated sarcomatous tissue, but precise histogenesis in not clear yet. This is a veryaggressive lesion and our fi ndings show that previous reports of indolent behaviour were preliminary.Spectrum of differential diagnosis, namely benign mixed tumor, phylloid tumor, primarybreast sarcoma and colloid carcinoma warrant clear knowledge about this unique entity.

Key words:
breast, metaplastic carcinoma, matrix-producing carcinoma, sarcomatoid carcinoma,heterologous, myoepithelial differentiation