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thyroid adenolipoma

Thursday 30 December 2021

The adenolipoma of the thyroid gland is considered a rare finding. It consists in a benign, encapsulated neoplasm composed of mature adipose tissue and glandular elements.

Adenolipomas or thyrolipomas are well-circumscribed benign neoplasm characterized by the presence of mature adipose tissue and glandular elements.

Adenolipomas may be associated with nodular goiter.

Histologically adenolipomas are isolated lesions surrounded by a fibrous capsule, composed of mature adipose tissue (from 10 to 90%) and proliferation of follicles without cytologic atypia, capsular or vascular invasion. Small connection with perithyroidal fatty tissue are described (“scoop”-sign).

Differential diagnosis

The differential diagnosis of macroscopic fat-containing thyroid lesions mainly includes thyrolipomatosis and amyloid goiter.

The first one is characterized by diffuse infiltration of the normal parenchyma by mature adipose tissue between follicles and no evidence of a capsule. Stromal fibrosis and lymphocytic aggregates are occasionally observed.

Amyloid goiter is associated with systemic disease and histologic evidence of amyloid deposition (confirmed with special stains, e.g. Congo red) both in the thyroid parenchyma and in other organs.

The expression of thyroglobulin and absence of parathormone (PTH) and cytoplasmic glycogen differentiate thyroid adenolipomas from ectopic parathyroid tissue or ectopic parathyroid lipoma.

Other pathologic conditions associated with the presence of adipose tissue are lymphocytic thyroiditis, Grave disease, encapsulated papillary carcinoma and liposarcoma.

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