Clonal analysis of human adrenocortical carcinomas and secreting adenomas

Adrenocortical tumours in man are characterized mainly on biochemical, anatomical and histological grounds which establish their secretory pattern and, with some uncertainty, their benign or malignant nature. To study further these tumours and eventually to shed some light on their pathogenesis, we determined their clonal composition.

Clonal composition was determined by X-chromosome inactivation analysis on tumour and leucocyte DNA using three markers: M27 beta, phospho-glycero-kinase (PGK) and hypoxanthine-phosphoribosyl transferase (HPRT) with 88, 33 and 27% heterozygosity rates respectively.

Clonal analysis was performed on 25 tumours from 19 heterozygous female patients: four had a carcinoma, 14 had a single secreting adenoma, and one had autonomous bilateral macronodular hyperplasia with Cushing's syndrome (seven adenomas examined).

The malignant tumours had patterns indicative of monoclonality. The single adenomas displayed contrasting results with patterns indicative of monoclonality in eight cases, and patterns indicative of polyclonality in six cases; monoclonal adenomas were larger and had a higher prevalence of nuclear pleomorphism than the apparently polyclonal adenomas. In the patient with bilateral macronodular hyperplasia, different clonal patterns were present in different adenomas: whereas a clear monoclonal pattern was observed in the three adenomas of the right gland, in which the active X-allele was not always the same, in two interpretable adenomas of the left gland, a moderately skewed pattern suggested a partial monoclonal component.

These data show that adrenocortical carcinomas are monoclonal and suggest that adenomas may arise from a single cell or from more than one cell under the putative action of local growth factors. In adenomas, which until now had appeared homogeneous, this genetic heterogeneity may reflect different pathophysiological mechanisms or it may represent different stages of a common multistep process exceptionally occurring in a single patient with bilateral macronodular hyperplasia.