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Table 1 World Health Organization histologic classification of metaplastic breast cancer

From: Metaplastic breast cancer: histologic characteristics, prognostic factors and systemic treatment strategies

Epithelial type metaplastic breast cancer Histologic features
Squamous cell carcinoma Infiltrating squamous carcinoma with polygonal cells, eosinophilic cytoplasm and possible keratin pearl formation.
Adenocarcinoma with spindle cell differentiation Poorly cohesive sheets of predominant spindle cell morphology; resembles a low grade sarcoma.
Adenosquamous carcinoma Glands display varying degrees of squamous differentiation, characterized by pavement-like architecture, prominent intercellular bridges and, to a lesser extent, keratin formation.
Mixed-type metaplastic breast cancer Histologic features
Carcinoma with chondroid metaplasia Immunoreactive for S-100, patchy for cytokeratin while being negative for smooth muscle antigen.
Carcinoma with osseous metaplasia Infiltrating carcinoma with osseous differentiation of the mesenchymal component.
Carcinosarcoma Infiltrating carcinoma with a malignant mesenchymal component.
  1. Adapted from Tavassoli FA, Devilee P: World Health Organization classification of tumors: tumors of the breast and female genital organs. Pathology and genetics of tumors of the digestive system. In World Health Organization Classification of Tumors. Lyon, France: IARC Press; 2003:37-41 [33].