Genetic aspects of pheochromocytoma

Pheochromocytomas are derived from chromaffin cells of the adrenal medulla which synthesize and secrete catecholamines, thus affecting the cardiovascular system and metabolic processes. Pheochromocytoma is a tumor of the following multicarcinoma hereditary syndromes: type 2 multiple endocrine neoplasia, von Hippel-Lindau disease, type 1 neurofibromatosis and the pheochromocytomas/paragangliomas syndrome. Pheochromocytomas are relatively rare, and because of non-specific manifestation of these tumors and the possible lack of signs and symptoms for extended periods of time, the diagnosis may be delayed, which may, in turn, lead to death. Pheochromocytomas may occur sporadically. However, due to the frequent incidence of hereditary forms of these cancers, the presymptomatic genetic testing of family members with a positive family history is indicated, thus allowing for selecting people with higher risk of cancer. Early detection of the syndrome and the coexisting tumors (which may be malignant) may lead to a correct diagnosis, regular surveillance, preventive examinations and implementation of appropriate early treatment. Recent examinations have shown significant involvement of RET, VHL, NF1, SDHB and SDHD as well as the newly discovered KIF1Bβ, TMEM127 and MAX genes in pathogenesis of these tumors. The microarray-gene expression studies, based on the analysis of cellular pathways, have revealed two distinct clusters indicating two different routes of tumorgenesis. The genotype-phenotype correlations are still being studied and future research can give us clearer information about the function of these genes, which may prove crucial from the clinical point of view.