Objective  The aim of this study was to summarize the etiology and clinical characteristics ofpatients with indistinguishable sellar lesions, and to explore the clinical value and safety of biopsy by endoscopic trans-sphenoidal approach.

  Methods  The clinical data were retrospectively collected and analyzed in patients with indistinguishable sellar lesions who underwent biopsy by the endoscopic trans-sphenoidal approach (ETA) or endoscopic extended trans-sphenoidal approach (EETA) in Peking Union Medical College Hospital from July 1, 2011 to July 1, 2019, including the etiology, clinical manifestations, laboratory examinations, radiological features, and postoperative complications.

  Results  A total of 142 patients who met the inclusive criteria were enrolled in this study. ETA biopsy was performed in 115 patients (81.0%, 115/142) and EETA in 27 patients (19.0%, 27/142). The etiology included:cystic lesions in 12 patients (8.5%, 12/142), inflammatory/infectious diseases in 30 patients (21.1%, 30/142), and tumors in 100 patients (70.4%, 100/142). The most common diseases were germ cell tumors (79 patients), Langerhans cell histiocytosis (8 patients), Rathke's cysts (8 patients), and lymphocytic hypophysitis (7 patients). The clinical manifestations of patients with this type of disease frequently lacked specificity. Among the 142 patients, the most common manifestations were those related to central diabetes insipidus. There were no patients with elevated alpha-fetoprotein in the cerebrospinal fluid and 29 patients with elevated beta-human chorionic gonadotropin in the cerebrospinal fluid. Among these 29 patients, 27 (93.1%) were germ cell tumors and 2 (6.9%) were craniopharyngiomas. Tumors and inflammatory/infectious diseases most often involved both the sella and pituitary stalk (25.0%, 33.3%), followed by the sella or protruding from the sella (21.0%, 30.0%). Cystic lesions most often involved the sella or protruding from the sella (75.0%). The disappearance of bright spots in the posterior pituitary was discovered in 97.0% of patients. Within 1 month after the biopsy, 7 patients (4.9%, 7/142) had central nervous system infection; 3 patients (2.1%, 3/142) had cerebrospinal fluid leakage with 2 of them recovered after surgical repair. Three patients (2.1%, 3/142) had worsened eye movement; 2 (1.4%, 2/142) had worsened visual acuity; 2 (1.4%, 2/142) had a decreased visual field, who have recovered basically after treatment.

  Conclusions  The clinical characteristics of lesions in the sellar area frequently lack specificity. Histopathological examination is the gold standard of diagnosis. Endoscopic trans-sphenoidal biopsy in the sellar area is safe and reliable.