cDNA microarray analysis assists in diagnosis of malignant intrarenal pheochromocytoma originally masquerading as a renal cell carcinoma.

Intrarenal pheochromocytoma (paraganglioma) is a very rare tumour. Its diagnosis is often difficult to establish because of its rarity and its histological similarity to renal cell carcinoma (RCC). Recently, we examined the molecular signatures of different subtypes of kidney tumours by using cDNA microarray. The signature pattern for one tumour, which was originally diagnosed as granular cell RCC, was clearly distinct from that of any other subtype of kidney tumour, and led us to re-evaluate the case. Haematoxylin and eosin staining revealed histological features suggestive of pheochromocytoma, and immunohistochemical studies showed positive staining for neuroendocrine markers but not for keratin. A germline missense mutation, D119E, in the familial paraganglioma related gene succinate dehydrogenase subunit D (SDHD), was subsequently identified. The treatment modality was revised and radiotherapy was given, to which the patient responded, leading to a reduction in tumour size of 25% within the first month. To our knowledge, this is the first report of an intrarenal pheochromocytoma that was diagnosed with the assistance of cDNA microarray analysis.