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Metaplastic carcinomas of the breast are uncommon breast tumors with aberrant cellular differentiation, most commonly showing ductal, squamous, and mesenchymal components. A breast carcinoma composed of both epithelial and melanocytic differentiation is rare, with only four previously reported cases in the literature. We present the fifth reported case, where the diagnosis was suggested by fine‐needle aspiration (FNA) and later confirmed after the surgical specimen was excised. Histologically, this neoplasm revealed multidirectional differentiation, consisting primarily of squamous and melanocytic cell types, with focal glandular and osseous metaplasia. Based on the morphologic, immunohistochemical, and ultrastructural findings, we conclude that such tumors fall within the spectrum of metaplastic carcinomas of the breast. We believe that this case will further contribute to the understanding of this enigmatic tumor. Diagn. Cytopathol. 23:46–50, 2000. © 2000 Wiley‐Liss, Inc.

Metaplastic carcinomas of the breast are uncommon breast tumors with aberrant cellular differentiation, most commonly showing ductal, squamous, and mesenchymal components. A breast carcinoma composed of both epithelial and melanocytic differentiation is rare, with only four previously reported cases in the literature. We present the fifth reported case, where the diagnosis was suggested by fine-needle aspiration (FNA) and later confirmed after the surgical specimen was excised. Histologically, this neoplasm revealed multidirectional differentiation, consisting primarily of squamous and melanocytic cell types, with focal glandular and osseous metaplasia. Based on the morphologic, immunohistochemical, and ultrastructural findings, we conclude that such tumors fall within the spectrum of metaplastic carcinomas of the breast. We believe that this case will further contribute to the understanding of this enigmatic tumor.

Invasive ductal carcinoma of the breast with clear cell changes is a very rare pathological entity. There are <150 cases of this breast cancer subtype reported in the literature. Clear cell carcinoma could be easily missed or under-diagnosed in a breast core biopsy specimen due to the fact that this subtype tends to show a papillary pattern with clear cell and pseudo-lactating changes, especially in young female patients. Normal breast tissue may possess clear cells as a consequence of the physiological changes of pregnancy, the clearing of the cytoplasm within myoepithelial cells, or the clearing of the cytoplasm in apocrine metaplasia. Owing to its aggressive clinical course, clear cell carcinoma must be differentiated from other subtypes of breast carcinoma. Special attention given to this rare subtype by pathologists and clinicians could avoid misdiagnosis and delay of treatment.