Clonal patterns in phaeochromocytomas and MEN-2A adrenal medullary hyperplasias: histological and kinetic correlates

The relationship among histological features, cell kinetics, and clonality has not been studied in adrenal medullary hyperplasias (AMHs) and phaeochromocytomas (PCCs). Thirty-four PCCs (23 sporadic and 11 MEN-2A (multiple endocrine neoplasia type 2A)-related tumours, the latter associated with AMH) from females were included in this study. Representative samples were histologically evaluated and microdissected to extract DNA and evaluate the methylation pattern of the androgen receptor alleles. At least two tissue samples (from the peripheral and internal zones in each tumour) were analysed with appropriate tissue controls run in every case. The same areas were selected for MIB-1 staining and in situ end labelling (ISEL). Malignant PCCs were defined by histologically confirmed distant metastases. All monoclonal AMH nodules from the same patient showed the same X-chromosome inactivated. Six sporadic PCCs revealed liver metastases (malignant PCC) and eight additional sporadic PCCs showed periadrenal infiltration (locally invasive PCC). All informative PCCs were monoclonal, except for five locally invasive PCCs and one benign PCC that revealed polyclonal patterns. Those cases also showed a fibroblastic stromal reaction with prominent blood vessels, focal smooth muscle differentiation, and significantly higher MIB-1 (126.8+/-29.9) and ISEL (50.9+/-12.8) indices. Concordant X-chromosome inactivation in nodules from a given patient suggests that MEN-2A AMH is a multifocal monoclonal condition. A subgroup of PCCs characterized by balanced methylation of androgen receptor alleles, high cellular turnover, and stromal proliferation also shows locally invasive features.