Matrix-producing metaplastic breast carcinoma – a rare malignancy

Background

Metaplastic breast carcinomas are ductal carcinomas that undergo metaplasia into non-glandular growth patterns. They are very rare, accounting for less than 1% of all invasive mamma-ry carcinomas. Most patients present with a rapidly enlarging palpable mass that appears on mammography as a well-delineated mass [1].

Case Report

A 33-year-old female patient presented with a lump that appeared 5 months before in her left breast. On examination, a single 5×3 cm lump was palpable in the left breast in the upper outer quadrant. The lump was nontender, firm, and mobile, with skin involvement present. Axillary lymph nodes were not palpable. Systemic examination results were within normal limits, with no clinical evidence of distant metastasis. Results of hematological investigations, biochemistry profiles, and metastatic workup were normal.

FNAC of the lump was positive for malignant cells. The patient was staged as T4 N0 M0 as per the TNM classification system. The patient underwent modified radical mastectomy with axillary clearance. The histopathological report showed matrix-producing carcinoma with infiltrating duct carcinoma. The tumor was positive for the immunohistochemical markers keratin, EMA (Epithelial Membrane Antigen), and S100, thus confirming it to be matrix-producing breast carcinoma. Axillary lymph nodes were negative for malignant cells. After surgery, the patient recovered uneventfully.

Discussion

Matrix-producing breast carcinoma is a rare type of metaplastic carcinoma, characterized by a ductal carcinomatous element with direct extension to areas showing cartilaginous or osseous differentiation, and lacking an interspersed spindle cell component. It has better prognosis than metaplastic carcinoma [2].

Matrix-producing carcinoma accounts for less than 1% of all neoplastic breast lesions. Their presentation and mammographic appearance is similar to invasive mammary carcinomas. They are firm-to-hard, nodular, and circumscribed. Immunohistochemically, they are positive for keratin, EMA (epithelial membrane antigen), and S100. Matrix-producing tumors are S100 reactive and nonreactive for cytokeratin [1]. They are usually ER- and PR-negative [2].

Approximately 70–80% of metaplastic breast carcinomas over-express the epidermal growth factor receptor (EGFR), about 28% harbor EGFR amplification, and they lack estrogen receptor. Therefore, some patients might benefit from novel therapies targeting EGFR, such as EGFR tyrosine kinase inhibitors [3].

The average patient age is 58 years. Surgery remains the mainstay of therapy, either mastectomy or local excision [4]. Axillary lymph node metastasis varies from 6% to 25%. The 5-year survival rate for patients following mastectomy is 70% and for local excision it is 50% [4]. The overall 5-year survival rate for metaplastic breast carcinoma is 38% to 65%. Radiotherapy and chemotherapy are of limited effectiveness [4]. They a have better 5-year survival rate and less frequent nodal metastasis [2].

Conclusions

Poor prognostic factors include large tumors, nodal metastasis, poorly differentiated tumors, diffuse cellularity of the stromal matrix, and atypical cartilaginous metaplasia [1,4]. The prognosis of metaplastic breast carcinoma is worse than the same stage no special type (NST) breast carcinoma [5].