Medulla

Phaeochromocytoma: induces all its clinical manifestations through the production of catecholamines, which may be intermittent and life-threatening. Known as the 10% tumour (approximately 10% are bilateral, 10% are extra-adrenal, up to 10% are malignant), there is a strong association with multiple endocrine neoplasia (MEN) type 2A, von Hippel-Lindau disease and neurofibromatosis type 1. Extra-adrenal phaeochromocytomas, or paragangliomas, are morphologically identical and are most commonly found in the retroperitoneum, mediastinum, carotid body and urinary bladder. These have a higher incidence of malignant behaviour. Phaeochromocytomas average 3-5 cm in diameter and 75-150 g in weight and are therefore usually easily seen on radiographic imaging with CT or MRI. They are soft, pale-to-tan-coloured often with mottled areas of congestion, haemorrhage or necrosis, focal cystic degeneration and a fibrous pseudocapsule. Histology characteristically shows well-defined nests of cells ("Zellballen") separated by a delicate fibrovascular stroma. Nuclear enlargement and pleomor-phism are common and are not an indication of malignancy, which is notoriously difficult to predict histologically. In fact, the presence of distant metastases is the only reliable criterion. Favoured metastatic sites include ribs and spine. Treatment is primarily surgical excision of the tumour, sometimes solely as a debulking procedure in the presence of advanced malignant disease. The overall five-year survival rate for phaeochromocytomas is under 50%. Background medullary hyperplasia is an indicator of familial disease.

Neuroblastoma: a paediatric tumour (80% occur < 4 years of age) of the sympathetic nervous system belonging to the family of "small, round, blue cell" tumours. Most present with an intraabdominal mass. Forty per cent arise in the adrenal glands, most of the remainder being retroperitoneal or intrathoracic. Ganglioneuroblastoma and ganglioneuroma represent better-differentiated counterparts which are seen in an older age group and less commonly involve the adrenal gland. The clinical and laboratory aspects of these highly specialised paediatric tumours will not be discussed further.

Miscellaneous conditions: chronic adrenalitis is usually secondary to inflammation in adjacent organs, e.g., chronic pyelonephritis; adrenal haemorrhage (secondary to sepsis, shock, coagulopathy), cysts, myelolipoma (composed of fat and heamatopoietic tissue), lipoma, angioma, schwannoma and adenomatoid tumour (of mesothelial origin) are all occasionally encountered in surgical pathology practice.

Other malignant neoplasms: sarcomas (most commonly leiomyosarcoma) are very rare in the adrenal gland; malignant melanoma and malignant lymphoma/leukaemia usually secondarily involve the adrenals but may rarely be primary; metastatic carcinoma is the commonest pathological lesion and can closely mimic primary adrenal carcinoma (lung, breast and kidney most common primary sites).

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