Adrenal Gland - Accessory Adrenocortical Nodule
comment:Accessory adrenocortical nodules ( Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , and Figure 6 ) are fairly common in rats and mice. Also known by many other terms (e.g., ectopic adrenal tissue, accessory cortical tissue, hamartoma, accessory adrenal gland, supernumary adrenal, and adrenocortical rest), accessory adrenocortical nodules are minor developmental anomalies arising from partly or completely detached rests of the coelomic epithelial primordia from which the adrenal cortex is derived. They are most frequently located in contact with the capsule at one pole of the adrenal gland ( Figure 1 , Figure 2 , Figure 3 , and Figure 4 ) but can occur completely separated from the adrenal gland in the retroperitoneal fat ( Figure 5 and Figure 6 ), attached to the kidney capsule, or anywhere in the peritoneal cavity. In and of themselves, accessory adrenocortical nodules are almost always innocuous incidental findings without clinical or toxicologic relevance. However, they can develop the same degenerative, hyperplastic, and even neoplastic changes as the adrenal cortex proper.
Most nodules are spherical to ovoid structures surrounded by a usually delicate fibrous capsule and composed of well-differentiated zonae glomerulosa-type and fasciculata-type cells ( Figure 1 and Figure 2 ), sometimes admixed and sometimes arranged in typical layers. Some adrenocortical accessory tissue consists of less densely packed nests of more primitive-appearing cortical cells ( Figure 3 and Figure 4 ). The typical surrounding fibrous capsule distinguishes accessory adrenocortical nodules from focal cortical hyperplasia and from extracapsular protrusions of cortical tissue. Accessory nodules must also be distinguished from cortical adenomas and carcinomas, which exhibit cellular pleomorphism and atypia and loss of cortical layering but are not commonly encapsulated.
recommendation:Adrenal gland - Accessory adrenocortical nodule should be diagnosed whenever present, but a severity grade is not necessary. If a nodule is located in the periadrenal fat (separated from the adrenal gland), the tissue should be listed as periadrenal fat. If a nodule is associated with another organ (e.g., kidney), ectopic tissue of that organ is a more appropriate diagnosis (e.g., Kidney - Ectopic tissue, Adrenal gland).
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