1. ¹Pathology Division, Shizuoka Cancer Center Hospital and Research Institute, Nagaizumi-cho, Sunto-gun, Shizuoka, Japan
2. ²Cancer Diagnostics Research Division, Shizuoka Cancer Center Hospital and Research Institute, Nagaizumi-cho, Sunto-gun, Shizuoka, Japan
3. ³Division of Pathology, Yaizu City Hospital, Yaizu, Shizuoka, Japan
4. ⁴Institute for Molecular Science of Medicine, Aichi Medical University, Nagakute-cho, Aichi-gun, Aichi, Japan
5. ⁵Department of Molecular Interaction and Tissue Engineering, Institute for Frontier Sciences, Sakyo-ku, Kyoto, Japan

Correspondence: Dr K Kusafuka, DDS, PhD, Pathology Division, Shizuoka Cancer Center Hospital and Research Institute, 1007 Shimonagakubo, Nagaizumi-cho, Suto-gun, Shizuoka 411-8777, Japan. E-mail: k.kusafuka@scchr.jp

Received 21 May 2008; Revised 28 May 2008; Accepted 29 May 2008; Published online 11 July 2008.

Abstract

Matrix-producing carcinoma of the breast is a well-established entity in the group of metaplastic carcinoma, which is histologically characterized by myxochondroid matrix formation and is extremely rare. We describe here four additional cases of matrix-producing carcinoma of the breast. All cases of matrix-producing carcinoma show nest-like, sheet-like, and cord-like growth of tumor cells with cellular atypia, in addition to scattered cancer cells within myxoid or myxohyalinous stroma. Three of four cases showed an acellular or oligocellular matrix-rich zone in the center of the tumor. Immunohistochemically, cancer cells of all cases were positive for cytokeratins and epithelial membrane antigens and partially positive for sox9 and p63. Aggrecan and type II collagen, which are cartilage-specific matrix molecules, were deposited in the stroma of all cases. Type I and type IV collagens were also deposited on the stroma of all cases. These findings suggest that, although cancer cells of matrix-producing carcinoma of the breast are epithelial, they transdifferentiate to chondrocyte-like cells and produce cartilage-specific matrix molecules, which are useful markers for diagnosing matrix-producing carcinoma.