Pheochromocytoma Masked by Mutation in the TH Gene

Catecholamine and metanephrine concentrations in multiple blood and urine samples were consistently within the reference interval and not compatible with the diagnosis of a pheochromocytoma (Table 1). Because the adrenal mass was not hormonally active, its surgical resection was performed without preoperative care. Unfortunately, blood samples obtained before surgery were collected on heparin-coated tubes precluding serum chromogranin A assay. Because the unusual presentation of a "non- catecholamine-secreting pheochromocytoma" was in complete contradiction with the biochemical feature expected for these tumors, we studied the intratumoral protein expression of the main enzymes involved in catecholamine synthesis by means of immunohistochemistry on paraffin-embedded sections of the tumor biopsy.