For example, testicular germ cell tumors (TGCT) and neuroblastoma (NB) exhibit greater inclusion of TCF3-exon 18a than exon 18b, and pheochromocytoma and paragangliomas (PCPG) and adrenocortical carcinomas (ACC) exhibit the greater inclusion of TCF3-exon 18b than exon 18a. The gene discussed is TCF3; the disease is hereditary pheochromocytoma-paraganglioma.