Of the adrenocortical tumors, up to 80% are malignant adenocarcinomas which occur unilaterally and cause adrenal atrophy in the contralateral adrenal due to glucocorticoid suppression. These tumors may or may not be endocrinologically active.
In most dogs, the hormone produced and secreted by these tumors is cortisol. Yet, in some cases adrenocortical tumors produce mineralocorticosteroids, mainly aldosterone, or, very rarely, its active precursor deoxycorticosterone.
Adenocarcinomas of the adrenal are frequently locally invasive and in advanced cases metastasize via localized vein infiltration, with dissemination to the vena cava and liver, particularly if tumors are ≥ 1.5 cm in length (as measured ultrasonographically or grossly on post-mortem.
In rare cases, adrenal adenocarcinoma can be present with concurrent adrenal pheochromocytoma as well as developing as a secondary tumor which develops as a result of metastasis from other primary organ sites such as the lung.
Clinical signs of these tumors are usually related to symptoms of hyperadrenocorticism and diagnosis can be presumptive on ultrasonographic examination of the adrenals.
Definitive diagnosis requires adrenal biopsy and histological examination.
Treatment is usually curative with adrenalectomy, but in advanced cases where metastasis is evident, the prognosis is guarded.
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