Fibrous bodies are associated with lower GH production and decreased expression of E-cadherin in GH-producing pituitary adenomas

OBJECTIVE A retrospective study was conducted in order to elucidate the clinicopathological significance of fibrous bodies, a hallmark of the sparsely granulated variant of GH-producing pituitary adenomas. METHODS A total of 37 acromegalic patients, 14 men and 23 women, with pure GH adenomas were studied. Immunohistochemistry was performed with antibodies specific for cytokeratin 8 and 18 (CAM5.2), GH, prolactin and E-cadherin. The tumour volume was estimated with high-resolution magnetic resonance imaging. RESULTS The percentages of adenoma cells with dot-like immunoreactivity for CAM5.2, fibrous bodies, were variable, ranging continuously from 0 to 100%. An increased percentage was associated with a lower basal GH level per unit tumour volume, a lower GH response to a bromocriptine suppression test, decreased immunoreactivities for GH and prolactin, and a decreased expression of E-cadherin immunoreactivity. CONCLUSION GH adenomas could not be distinctly separated into those with or without fibrous bodies. Decreased expression of E-cadherin may be involved in formation of fibrous bodies and result in lower GH production.