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TTF-1 positive small cell cancers: Don't think they're always primary pulmonary!
Laurine Verset1, Marianna Arvanitakis, Patricia Loi
1Laurine Verset, Myriam Remmelink, Pieter Demetter, Departments of Pathology, Erasme University Hospital, Université Libre de Bruxelles, 1070 Brussels, Belgium.
Abstract:
Thyroid transcription factor 1 (TTF-1) plays a key role in morphogenesis of the lungs and is expressed in up to 90% of pulmonary small cell carcinomas. This explains why this marker is frequently used in the search for the primary origin of metastatic endocrine tumours. Here we report on a TTF-1 expressing mixed endocrine-exocrine carcinoma of the common bile duct in a patient with pulmonary nodules that did not appear to be neoplastic. TTF-1 positivity in pulmonary and extrapulmonary neuroendocrine tumours is reviewed, and we conclude that TTF-1 expression in neuroendocrine tumours of the small-cell type are not uncommon at extrapulmonary locations. Therefore, immunohistochemistry for TTF-1 in such tumours should be interpreted with caution.
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