TTF-1-positive primary papillary epithelial tumor of the sella with long-term recurrence after multiple resections

Primary papillary epithelial tumor of the sella is an extremely rare thyroid transcription factor-1 (TTF-1) positive tumor arising from the posterior pituitary and infundibular area and is often mistaken for a nonfunctioning pituitary adenoma. We report a young woman with a recurrent sellar-suprasellar mass over nearly a decade despite multiple transsphenoidal surgeries. The tumor showed progressive enlargement without hormone hypersecretion. Histopathology revealed a papillary epithelial neoplasm composed of bland cuboidal-to-columnar cells with apical snouting and inflammatory fibrovascular cores. Immunohistochemistry showed strong pancytokeratin, cytokeratin 7, and diffuse nuclear TTF-1 positivity, with negative pituitary hormone and transcription factor markers, confirming the diagnosis. The proliferation index was low. Complete excision was not feasible due to anatomical constraints, resulting in persistent residual disease. This case highlights the need to reconsider the diagnosis in long-standing recurrent sellar masses and emphasizes the importance of expert pathological assessment and prolonged follow-up in these rare tumors.