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microglandular adenosis

Sunday 29 November 2015

Definition: Microglandular adenosis has small round glands with eosinophilic secretions. It is an important mimic of mammary carcinomas because it can infiltrate surrounding tissue, and may not have a myoepithelial cell layer. It is benign, however, and the glands do have a basement membrane.

Images

- Microglandular adenosis: S100 positive, no myoepithelial layer p63- (mimics tubular carcinoma)

Microglandular adenosis shows round glands with eosinophilic PAS positive secretions and a layer of flat epithelial cells that stain positive for S100.

S100 can be useful in diagnosing microglandular adenosis, which is also positive for cytokeratins, CAM 5.2 and p63.

Microglandular adenosis is composed of a layer of flat epithelial cells that stain positive for S100 and characteristically have eosinophilic secretions that are PAS positive. They are frequently positive for cytokeratins as well.

These lesions should be excised, since they have been associated with nearby malignancy in up to 30% of cases.

Microscopy

- Small, regular glandular profiles occur within adipose tissue.
- Dilated ducts in the periphery contain microcalcifications.
- Glands maintain regular, smooth, round configuration and are surrounded by delicate fibrous tissue.

IHC

- Microglandular adenosis shows a layer of flat epithelial cells that stain positive for S100.

- S100 can be useful in diagnosing microglandular adenosis, which is also positive for cytokeratins / CKs , CAM 5.2 and p63.

- Microglandular adenosis is negative for GCDFP-1

- Microglandular adenosis is triple negative (- ER, PR, Her-2).

Differential diagnosis

- mammary small glandular proliferations

  • invasive mammary tubular carcinoma
    • In the case of invasive tubular carcinoma, the neoplastic glands are more irregular in shape and in direct contact with adipocytes.

See also

- adenosis

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