Endocrine Abstracts

Introduction: Folliculo-stellate cells (FSCs), non-endocrine star-like shaped population of cells located in the anterior pituitary, have very heterogenous function and phenotype. Located between the secretory cells, their first atributed role was connected to a supporting network. In literature, they were mentioned to be involved in the pathogenesis and evolution of pituitary neuroendocrine tumors (PitNETs).

Objectives: Analyse FSCs characteristics and distribution in a series of nonfunctioning PitNETs.

Materials and methods: Twenty-six nonfunctioning PitNETs obtained using transsphenoidal surgery were included. The diagnosis of ‘nonfunctioning tumor’ was based on the preoperative biochemistry. The histopathological diagnosis was performed using hematoxylin eosin morphological staining. Immunohistochemical (IHC) evaluation for anterior pituitary hormones was assesed for a proper classification of the tumors. FSCs were evaluated using glial fibrillary acidic protein (GFAP).

Results: Histopathologicaly, most PitNETs presented a papillary/ alveolar growth pattern, with acidophilic tinctoriality. Immunohistochemical hormonal profile revealed two silent somatotropinomas, three silent corticotropinomas, 14 silent gonadotropinomas (with IHC positivity for FSH/ LH/ both). Two cases were considered PitNETs with unusual immunohistochemical combinations, expressing both GH and ACTH. Five cases were negative for all anterior pituitary hormones. FSCs were described using GFAP. They presented stellate shape, with cytoplasmic prolongations among the tumoral cells. Also, these cells formed networks inside the tumors, with a tendency to locate near blood vessels. Nine out of twenty-six tumors showed IHC reaction for FSCs. Eight were silent gonadotropinomas and the ninth was considered silent corticotropinoma.

Conclusion: Although there are many studies regarding FSCs, their entire function remains poorly understood, both in normal and pathological pituitary gland. In this study, 57% of silent gonadotroph PitNETs contained FSCs among the tumoral cells. The PitNETs with negative expression for all anterior pituitary hormones didn’t express IHC positivity for FCSs. Further studies are needed in order to establish the link between these cells and PitNETs.