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WHO Classification of Tumours
Undifferentiated carcinoma
Region of the ampulla of Vater


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 / poorly differentiated carcinoma of the ampulla of Vater
There are two types of undifferentiated carcinoma of the ampulla:

(1) The first is composed of small (non-neuroendocrine) cells while in the second type spindle cells predominate and resemble a sarcoma (sarcomatoid carcinoma). The first type is highly cellular with minimal stroma and is composed of relatively small cells with scant cytoplasm, vesicular nuclei and prominent nucleoli arranged in solid sheets or nests

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Albores-Saavedra J, Henson DE, and Klimstra DS eds.
Tumors of the Gallbladder, Extrahepatic Bile Ducts, and Ampulla of Vater
Armed Forces Institute of Pathology: Washington, DC 2000

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Molberg KH, Heffess C, Delgado R, Albores-Saavedra J (1998)
Undifferentiated carcinoma with osteoclast-like giant cells of the pancreas and periampullary region.
Cancer 82: 1279-87

. There are no glands or signet-ring cells. Numerous mitotic figures and necrosis of variable extent are common. Immunohistochemical stains for neuroendocrine markers are negative.

(2) The second type of undifferentiated carcinoma consists predominantly of fascicles of spindle cells, some of which are keratinpositive, supporting their epithelial phenotype. When extensively sampled, these tumours often contain glandular structures or nests of frank epithelial cells. Considerable cytological atypia including the presence of pleomorphic and anaplastic giant cells may be present in the spindle cell component. When heterologous elements such as cartilage, bone and skeletal muscle are present, the term “carcinosarcoma” is justified

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Kijima H, Takeshita T, Suzuki H, Tanahashi T, Suto A, Izumika H, Miki H, Terasaki Y, Nakamura M, Watanabe H, Tamaoki N, Omiya H (1999)
Carcinosarcoma of the ampulla of Vater: a case report with immunohistochemical and ultrastructural studies.
Am J Gastroenterol 94: 3055-9

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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