Year : 2008 | Volume
: 51 | Issue : 2 | Page : 263--264
Matrix-producing mammary carcinoma: A rare breast tumor
Kavita Mardi, Jaishree Sharma
Department of Pathology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India
12-A, Type V Quarters, GAD Colony, Kasumpti, Shimla, H.P
Matrix-producing carcinoma of the breast is a unique subclass of metaplastic carcinoma which is characterized by the existence of a ductal carcinomatous component with direct transition to areas showing cartilagenous or osseous differentiation, lacking an interspersed spindle cell component. This article reports one such rare case in a 50-year-old woman who had a right breast mass. f0 ine needle aspiration (FNA) smears showed abundant chondromyxoid extracellular matrix to which were variably admixed carcinomatous cells. Histological examination revealed a neoplasm composed of invave ductal carcinoma with a direct transition to chondrosarcomatous areas. The case is reported not only for its peculiar microscopic characteristics but also to highlight its better prognostic features and hence, the need for its recognition.
|How to cite this article:|
Mardi K, Sharma J. Matrix-producing mammary carcinoma: A rare breast tumor.Indian J Pathol Microbiol 2008;51:263-264
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Mardi K, Sharma J. Matrix-producing mammary carcinoma: A rare breast tumor. Indian J Pathol Microbiol [serial online] 2008 [cited 2020 Jul 5 ];51:263-264
Available from: http://www.ijpmonline.org/text.asp?2008/51/2/263/41682
Metaplastic carcinomas of the breast encompass a histologically diverse spectrum. Among these, matrix-producing carcinoma (MPC) represents a rare and distinctive entity. The identification of this entity is important to pathologists as well as surgeons, considering its superior prognosis to other metaplastic carcinomas. This report highlights one such case with cytomorphological and histopathological correlation, along with a review of pertinent literature and differential diagnosis.
A 50-year-old woman presented with a breast lump of 1-year duration, with a history of rapid increase in its size since 2 months. On examination, a firm, non-tender, mobile lump 2°cm × 2 cm was present in the upper outer quadrant of right breast. f0 ine needle aspiration (FNA) smears of the lump were characterized by an abundant chondroid extracellular matrix to which were variably admixed carcinomatous and chondroid type cells [Figure 1]. Duct cell carcinoma component was also seen in the form of irregular angulated clusters of highly pleomorphic cells with high N/C ratio, hyperchromatic nuclei with prominent nucleoli and irregular nuclear membrane. Isolated plasmacytoid tumor cells were also seen in the background. Cytodiagnosis of metaplastic carcinoma of the breast was rendered. The patient underwent modified radical mastectomy. On serial sectioning of the specimen, a 2 cm × 2 cm gray white infiltrative growth was identified. On microscopic examination, a poorly differentiated infiltrating duct carcinoma was seen, comprising nests and trabaculae of cells with a moderate amount of cytoplasm, a high N/C ratio, anisokaryosis and prominent nucleoli (Modified Bloom-Richardson grade 3). There was direct transition of these areas into chondromyxoid matrix in which were embedded highly pleomorphic tumor cells (grade III chondrosarcoma). An intervening spindle cell component was absent [Figure 2] and [Figure 3]. With the above features, a diagnosis of MPC of the breast was made. The tumor was ER and PR negative.
Matrix-producing carcinoma is a very rare breast neoplasm accounting for less than 0.1% of all breast malignancies.  MPC is a unique subtype of metaplastic carcinoma, characterized by the existence of an overt ductal carcinomatous component with a direct transition to areas showing cartilagenous or osseous differentiation, lacking an interspersed spindle cell component.  Wargotz and Norris  first described this entity in their study of 26 cases of metaplastic carcinomas. They found that the carcinomatous component was moderately-to-poorly differentiated with a frequent association of intraductal component. The nature of matrix was variable, ranging from bland cartilage to a typical chondroid to osteoid to overt bone formation. The matrix was made up of acid mucopolysaccharides that stained metachromatically with alcian blue and aldehyde fuschin and was resistant to hyaluronidase and diastase.
Pathogenesis of such diverse elements within obviously infiltrating carcinoma has been the subject of controversy. Ultra-structural analysis of MPC supports the evidence that the tumor cells are of epithelial and myoepithelial derivation.  Myoepithelial cells differentiate along mesenchymal lines and produce a gamut of matricial appearances. After the advent of immunohistochemistry, it is now generally accepted that metaplasia of the epithelial elements of carcinoma gives these lesions their pseudosarcomatous appearance. 
Matrix-producing mammary carcinomas may have a varied presentation on fine needle aspiration samples. Characteristic cytomorphological features include an abundant chondroid extracellular matrix to which were variably admixed carcinomatous and chondroid type cells with variable degree of atypia. Giemsa-stained smears demonstrate the extracellular metachromatic stromal elements more clearly than Papanicolau-stained smears. Use of Diff quik stain can also be very useful in the identification of stroma in this neoplasm.  The spectrum of differential diagnosis to be considered encompasses a number of benign and malignant entities like malignant fibroepithelial lesions with myxochondroid stroma and true sarcomas of the breast with cartilagenous metaplasia.  However, only 57% of cases show both ductal carcinoma and metaplastic component. Thus, in almost one-half of the cases, the diagnosis is not possible by FNA. 
The heterologous chondroid component of MPC can be present in two patterns. One displays a typical structure of low-grade hyaline cartilage and the second pattern shows epithelial tumor cells embedded in homogenous eosinophilic extracellular matrix giving an appearance of chondroid aura.  Cartilagenous metaplasia may be uncommonly noted in other mammary tumors such as fibroadenoma, phyllodes tumor and even pleomorphic adenoma. The unequivocal presence of carcinoma is a helpful distinguishing feature in such cases. These tumors are usually estrogen and progesterone receptor negative. 
The identification of this entity is important to pathologists and surgeons alike, considering its superior prognosis to other metaplastic carcinomas. The peculiarity of these tumors is that though they are composed of a mixture of high-grade infiltrating duct carcinoma and areas of heterologous stroma, each of which is known to behave aggressively, these composite tumors have a better 5-year survival rate and less frequent nodal metastasis. 
In conclusion, matrix-producing mammary carcinoma, because of its distinctive histological and cytomorphological features, peculiar clinical behavior and spectrum of differential diagnosis warrants clear knowledge about this unique entity. As a rare entity, MPC of the breast deserves a separate position in tumor classification.
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