OBJECTIVE: Presentation of variable morphology of the so-called matrix-producing carcinoma, the rare variant of metaplastic breast carcinoma. Establish the extent of myoepithelial phenotype by immunohistochemistry and assess behaviour of the lesion. DESIGN: Review of clinicopathologic data of 11 cases. SETTING: Private Biopsy Lab s.r.o., Pilsen and Sikl's Department of Pathology, Charles University and Faculty Hospital, Pilsen. METHODS: Included are eleven cases from Breast Registry, Biopsy Lab s.r.o., Pilsen and Pathology Department, Faculty Hospital in Hradec Králové and Martin and from Biopsy Lab in Horovice. Analyzed were morphology, stage, grade and follow up. Myoepithelial phenotype was demonstrated immunohistochemically by LSAB+ system (DAKO) and seven conventional myoepithelial markers (GFAP, aktin S, calponin, cytokeratin 14, p63, CD10 and P-cadherin) were used. Oncogene p53 and Her2/neu were also detected. RESULTS: Matrix-producing carcinoma is an extremely rare type of metaplastic carcinoma of the breast, where high-grade epithelial component continually merges with heterologous mesenchymal chondroid component without overt spindle cell sarcomatoid pattern in between. There were all women at the age of 32 to 86-years (average 54 years, median 52 years) and the maximum tumor diameter ranged from 18 to 60 mm (average 32 mm). The axillary LN was positive in six cases in the time of diagnosis. The follow up available in 9 women ranged from three months to ten years (average 24 months); dissemination of the disease was observed in three cases; 2 of these patients died of disease after three and ten years, respectively. The heterologous mesenchymal chondroid component was produced in two different ways; one displayed typical structure of low-grade hyaline cartilage, in the second one the epithelial tumorous cells were embedded in the homogenous eosinophilic extracellular matrix giving appearance of chondroid aura. Metaplastic component constituted 5-75% of the tumor volume. Immunohistochemical evidence of myoepithelial differentiation in all neoplasms was demonstrated, 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 identified in six cases, all tumors were Her2/neu negative. Histologically the metastases were formed either by carcinoma cells only, or more frequently, they replicated the structure of primary lesion. CONCLUSION: As a rare entity, matrix-producing carcinoma of breast displaying myoepithelial phenotype, deserves separate position in tumor classification. It differs from conventional myoepithelial carcinoma and from heterologous metaplastic carcinoma, where the matrix emanate from undifferentiated sarcomatous tissue, but precise histogenesis in not clear yet. This is a very aggressive lesion and our findings show that previous reports of indolent behaviour were preliminary. Spectrum of differential diagnosis, namely benign mixed tumor, phylloid tumor, primary breast sarcoma and colloid carcinoma warrant clear knowledge about this unique entity.

A total of 21 metaplastic breast carcinomas (MCs) with chondroid differentiation were evaluated to better establish the clinicopathological features of this variant. The tumors exhibited mainly invasive carcinoma admixed with areas of cartilaginous matrix production. An associated ductal intraepithelial neoplasia component grade 2 or 3 was observed in 43% of cases. Immunohistochemical analysis revealed a triple negative (ER-, PR-, and Her2/neu-) immunoprofile and no expression of the androgen receptor. EGFR-positivity was found in 88% of evaluated cases, consistent with the proposed basaloid phenotype for all MC. Compared with previous studies that reviewed MC with osseus and cartilaginous elements, the incidence of axillary lymph node metastasis was significantly higher in our study and 60% of positive nodes exhibited chondroid differentiation. Available follow-up data (n = 10) revealed aggressive behavior of this MC variant with frequent metastasis, including visceral involvement and local chest wall recurrence despite chemotherapy and radiation. Three patients subsequently died of metastatic disease.

Chordoma originates from embryonic notochordal remnants in the midline along the spinal axis and is characterized by cords and lobules of neoplastic cells arranged within myxoid matrix. Because of histologic similarities with myxoid matrix and overlapping immunohistochemical profile, chondrosarcoma, myxopapillary ependymoma, and chordoid meningioma enter in the histologic differential diagnosis at this site. Therefore, the judicious use of a panel of selected immunostains is unquestionably helpful in diagnostically challenging cases. To find useful immunohistochemical markers for assisting in differential diagnosis between chordoma and other tumors with chordoid morphology, an immunohistochemical study using D2-40, epithelial membrane antigen (EMA), pan-cytokeratin (panCK), glial fibrillary acidic protein (GFAP), S-100 protein, galectin-3, neural cell adhesion molecule (NCAM), beta-catenin, E-cadherin, and carcinoembryonic antigen was performed on 14 chordomas, 7 chondrosarcomas, 9 myxopapillary ependymomas, and 4 chordoid meningiomas. Chordoma typically showed positive for EMA and panCK and negative for D2-40 and GFAP; whereas chondrosarcoma revealed positive for D2-40, and negative for EMA, panCK, and GFAP; myxopapillary ependymoma positive for GFAP and negative for EMA; and chordoid meningioma positive for EMA, and negative for panCK and GFAP. On the basis of our immunohistochemical study, a panel of D2-40, EMA, panCK, and GFAP allowed the correct recognition of all tumors examined. Other immunohistochemical markers including S-100 protein, galectin-3, NCAM, beta-catenin, E-cadherin, and carcinoembryonic antigen were of little value in differential diagnosis. In summary, the best immunohistochemical markers useful for the evaluation of tumors with chordoid morphology were D2-40, EMA, cytokeratin, and GFAP. D2-40 was a true chondroid marker to be useful for the differential diagnosis with chordoma.