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Int J Clin Exp Pathol 2010;3(6):629-633

Case Report
Primary small cell carcinoma of the breast with TTF-1 and neuroendocrine marker
expressing carcinoma in situ

Michael Christie, Laura Chin-Lenn, Monique M. Watts, Alpha E. Tsui, Malcolm R. Buchanan

Departments of Anatomical Pathology, Surgery and 3Medical Oncology, Royal Melbourne Hospital, Victoria, Australia

Received April 21, 2010, accepted April, 2010, available April, 2010

Abstract: Primary small cell carcinoma (SmCC) of the breast is very rare and may be difficult to distinguish from metastatic small cell
carcinoma. Confident histopathological diagnosis of a primary breast SmCC requires the demonstration of an in situ component. We report a
case of primary small cell carcinoma of the breast with coexisting carcinoma in situ in which the invasive carcinoma and in situ component
both expressed neuroendocrine markers and Thyroid transcription factor-1 (TTF-1) by immunohistochemistry. Expression of neuroendocrine
markers and TTF-1 in the in situ component allowed a highly confident diagnosis of primary small cell carcinoma of the breast. To our
knowledge there is only one previous report of TTF-1 expressing in situ carcinoma associated with a primary SmCC of the

Key words: Small cell carcinoma, breast, thyroid transcription factor-1, neuroendocrine, carcinoma in situ

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Address all correspondence to:
Michael Christie, MD
Department of Anatomical Pathology
Royal Melbourne Hospital
Grattan Street, Parkville
Victoria, 3050, Australia.
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