Adenoma granulation pattern correlates with clinical variables and effect of somatostatin analogue treatment in a large series of patients with acromegaly.

CONTEXT

Somatotroph adenomas have been classified into densely granulated (DG) and sparsely granulated (SG) tumours with a transitional, intermediate group. Gsp oncogenes are activating mutations in the Gsα subunit gene, found in approximately 40% of somatotroph adenomas.

OBJECTIVES

To explore granulation pattern and presence of gsp oncogene in acromegaly with correlations to clinical and biochemical variables and to the effect of treatment with somatostatin analogues (SA), as well as to describe granulation pattern in adenomas with and without SA pretreatment.

DESIGN/SETTINGS/PATIENTS: Seventy-eight patients with active acromegaly were included. Long-term SA efficacy was evaluated in 29 patients treated preoperatively and in ten treated postoperatively. Granulation pattern was examined, as were immunohistochemical analyses for E-cadherin and SSTR2a. Protein levels of E-cadherin and SSTR2a were measured (Western blot). Gsp mutation analysis was available for 74 adenomas.

RESULTS

DG adenomas and the transitional group had higher serum levels of IGF-1 per tumour volume than SG (P = 0·009; P = 0·005). Acute and long-term SA responses were lower in SG (P = 0·001; P = 0·043). No correlation between gsp mutation and granulation was found, and no difference in granulation pattern according to preoperative SA treatment was demonstrated. A significant correlation between granulation and E-cadherin was found, where SG had lowest immunohistochemical expression, substantiated by protein levels, and a highly significant gradient was observed from DG, through the transitional group, to SG.

CONCLUSIONS

Densely granulated adenomas were highly responsive to somatostatin analogues in contrast to SG adenomas. The transitional group behaved clinically more like DG adenomas. However, based on E-cadherin, a marker of dedifferentiation, the transitional group seemed to be a true intermediate.