title: Metaplastic carcinoma with extensive chondroid differentiation in the breast (chondroid carcinoma).
abstract: Metaplastic breast carcinoma is very rare, and metaplastic carcinoma with chondroid differentiation is even rarer. Here, we report a case of metaplastic carcinoma with extensive chondroid differentiation mimicking chondrosarcoma that was challenging to diagnose. The tumor was characterized by an abundant chondromyxoid matrix. The definitive area of classic invasive ductal carcinoma was minimal. The peripheral portion of the tumor showed increased cellularity with pleomorphism and definitive invasive growth. Tumor cells in the chondrosarcomatous areas were diffusely immunoreactive for S-100 protein, patchy positive for cytokeratin, but negative for epithelial membrane antigen (EMA). Tumor cells in carcinomatous areas were diffusely positive for cytokeratin, S-100 protein, and patchy positive for EMA. In both areas, tumor cells were negative for smooth muscle actin (SMA) and CD34, while oncoprotein p53 was overexpressed. When pathologists encounter breast tumors with chondroid differentiation, careful sampling and immunohistochemistry for cytokeratin and SMA are most helpful to differentiate metaplastic carcinoma from malignant phyllodes tumor and malignant adenomyoepithelioma.
authors.affiliation: Department of Pathology, Yongdong Severance Hospital, Yonsei University College of Medicine, 146-92 Dogok-dong, Gangnam-gu, Seoul 135-720, Korea.
authors.forename: Yee-Jeong
authors.initials: YJ
authors.lastname: Kim
authors.forename: Hyo-Seob
authors.initials: HS
authors.lastname: Shim
authors.forename: Hyde
authors.initials: H
authors.lastname: Lee
authors.forename: Woo-Hee
authors.initials: WH
authors.lastname: Jung
mesh_terms: D000199:Actins / Q000378:metabolism; D018952:Antigens, CD34 / Q000096:biosynthesis; D001943:Breast Neoplasms / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D002277:Carcinoma / Q000150:complications* / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000378:metabolism; D008679:Metaplasia; D008875:Middle Aged; D018396:Mucin-1 / Q000378:metabolism; D009130:Muscle, Smooth / Q000473:pathology; D009362:Neoplasm Metastasis; D009418:S100 Proteins / Q000737:chemistry
chemical_list: D000199:Actins; D018952:Antigens, CD34; D018396:Mucin-1; D009418:S100 Proteins; D007633:Keratins