Prognostic implications of folliculo-stellate cells in pituitary adenomas: relationship with tumoral behavior

Introduction. Despite progress in understanding its pathogenesis, there has not yet been found any independent predictive marker of aggressive behavior of pituitary adenomas, to facilitate the treatment and monitoring of patients. Aim. To analyze the expression of folliculo-stellate cells by immunostaining with S-100 protein, in a series of patients with pituitary adenomas followed for at least seven years. Patients and methods. A retrospective study of 51 patients diagnosed with a pituitary adenoma between 2006 and 2008 was performed, according to current criteria established by the World Health Organization. The S-100 expression in folliculo-stellate cells was immunohistochemically evaluated, correlating it with clinico-radiological and histopathological tumor parameters and post-operative progression/recurrence. Results. Of 51 tumors, 40 were classified as typical and 11 as atypical pituitary adenomas. Most typical pituitary adenomas showed positive folliculo-stellate cells for S-100 (mean: 3.93%); atypical had little/no cell S-100 positive (mean: 0.83%). There were no significant differences in the expression of S-100 with respect to age or sex of the patient, size, invasiveness or post-operative tumor recurrence. Conclusions. In our study group, with the exception of non-functioning adenomas immunopositive for prolactin, with the lowest and highest average of all subtypes in both groups (typical 0.25% vs atypical 9.24%; p = 0.0028), the predictive factor of tumor aggressiveness for pituitary adenomas, is not represented by a low value of S-100 in folliculo-stellate cells, not allowing select patients for intensive post-operative treatment.