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TTF-1 positive breast cancer: a cautionary tale
  1. Peter Ellery1,
  2. Nicholas Archard1,
  3. Ally Saetta2,
  4. Michael Gandy3,
  5. Mary Falzon1
  1. 1Department of Cellular Pathology, University College London Hospitals NHS Foundation Trust, London, UK
  2. 2Bart's and The London School of Medicine and Dentistry, London, UK
  3. 3UCL Advanced Diagnostics, University College London, London, UK
  1. Correspondence to Dr Peter M Ellery, Department of Cellular Pathology, 3rd Floor, Rockefeller Building, 21, University Street, London WC1E 6DE, UK; p.ellery{at}

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Expression of thyroid transcription factor-1 (TTF-1) by primary breast carcinoma and ductal carcinoma in situ (DCIS) is extremely rare and can potentially lead to diagnostic confusion. Here, we present an instructive case, including the first report of mutation analysis on such a tumour, and discuss the ways in which diagnostic pitfalls can be avoided in this situation.

Case report

A 69-year-old female non-smoker with a past medical history of hypertension presented to the emergency department with cough and a right breast lump. Examination of the right breast revealed a 60 mm mass at the 12 o'clock position, with no skin tethering or fixation to deep structures. Mammography and ultrasound showed a well-defined lobulated mass measuring 30.5 mm in the upper half of the right breast, consistent with malignancy. In addition, chest radiography showed a right paramediastinal swelling of uncertain significance. Core biopsy of the right breast mass showed a grade 3 invasive ductal carcinoma with high-grade DCIS. Immunohistochemistry showed the tumour cells to be negative for oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) (figure 1). In view of the unexplained lung lesion on radiology, TTF-1 …

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  • Contributors We confirm that all authors fulfil the criteria for authorship.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.