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WHO Classification of Tumours
Undifferentiated carcinoma


Undifferentiated carcinoma is a usually aggressive, malignant epithelial neoplasm composed of atypical cells which do not display evidence of glandular, squamous, or urothelial cell differentiation.

Undifferentiated carcinoma of the esophagus lacks definite microscopic features of squamous differentiation. The tumour cells form nestsand sheet-like arrangements. Immunohistochemically, tumours express squamous epithelial markers. Such neoplasms must be distinguished from neuroendocrine/small cell neuroendocrine carcinoma (NEC). Undifferentiated carcinoma is negative for neuroendocrine

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Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010