Poster Presentation ESA-SRB-ANZOS 2025 in conjunction with ENSA

An unusual sella lesion expressing TTF-1  (128707)

Michael Fogarty 1 2 , Melisa Vazquez 3 , Thuy Vu 1 2
  1. Endocrinology and Diabetes, Austin Health, Heidelberg, Victoria, Australia
  2. Endocrinology and Diabetes, Northern Health, Epping, Victoria, Australia
  3. Anatomical Pathology , Austin Health, Heidelberg, Victoria, Australia

Background
Lesions expressing Thyroid-Transcription-Factor-1(TTF-1) are a rare subset of suprasella lesions. TTF-1 is a tissue-specific transcription factor expressed in differentiated cells derived from the foregut endoderm and neuroectoderm including thyroid follicular cells and type-II alveolar epithelial cells. We describe an atypical lesion with strong TTF-1 expression, and atypical morphology.

Case

A 48-year-old woman with minimal past medical history presented following a finding of a pituitary fossa lesion on CT investigation of chronic headaches. MRI demonstrated a 22x21x21mm mixed cystic and solid pituitary lesion with partial enhancement, favouring a cystic pituitary adenoma over a Rathke’s cleft cyst. There were no pituitary axis hormonal deficits on biochemical evaluation, nor suggestive clinical symptoms. During surgery, a heterogenous tumour was found with a large component described as a yellow, waxy, and cheese like in consistency.

Histopathological examination described tumour cells comprising cuboidal and columnar epithelioid cells within cohesive glandular/rosette-like structures, papillary-like structures and solid areas. There were some pleomorphic nuclei, with occasional atypical mitoses. Immunohistochemistry demonstrated TTF-1, cytokeratin 7 and Cam 5.2 positivity. Synaptophysin and all anterior pituitary hormone stains were negative. The Ki67 was estimated at 20%.

Considering the tumour morphology, atypical mitoses and TTF-1 positivity, differential diagnoses of metastatic thyroid carcinoma1 or lung adenocarcinoma2 were considered, however PET/CT and thyroid ultrasound studies did not reveal avid extracranial disease. TTF-1 expression is also strongly found in pituicytes3, raising differentials of rarer sella tumours including pituicytomas, although the morphology was not suggestive. Primary papillary epithelial tumour of the sella4 has been considered, however elevated Ki67 and mitoses and have not been described in these exceedingly rare cases.

Conclusion

Thus far we have described a suprasella mass without a clear histopathological diagnosis. Our patient is well post-operatively, will undergo serial MRI with consideration of repeat PET/CT to continue to investigate the origins of this lesion.

  1. 1. Guan L, Zhao X, Tang L, et al. Thyroid Transcription Factor-1: Structure, Expression, Function and Its Relationship with Disease. Biomed Res Int. 2021;2021:9957209. Published 2021 Sep 28. doi:10.1155/2021/9957209
  2. 2. Cai YC, Banner B, Glickman J, Odze RD. Cytokeratin 7 and 20 and thyroid transcription factor 1 can help distinguish pulmonary from gastrointestinal carcinoid and pancreatic endocrine tumors. Hum Pathol. 2001;32(10):1087-1093. doi:10.1053/hupa.2001.28245
  3. 3. Lee EB, Tihan T, Scheithauer BW, Zhang PJ, Gonatas NK. Thyroid transcription factor 1 expression in sellar tumors: a histogenetic marker?. J Neuropathol Exp Neurol. 2009;68(5):482-488. doi:10.1097/NEN.0b013e3181a13fca
  4. 4. Roncaroli F, Chatterjee D, Giannini C, et al. Primary papillary epithelial tumour of the sella: expanding the spectrum of TTF-1-positive sellar lesions. Neuropathol Appl Neurobiol. 2020;46(5):493-505. doi:10.1111/nan.12622