Benign Sclerosing Lesions of the Breast

The 3 entities are sclerosing adenosis, radial scar (complex sclerosing lesion) and microglandular adenosis.

Sclerosis adenosis:

A lobulocentric lesion (arise in association with the terminal duct lobular unit) with distorted obliterated glands with a myoepithelial layer in a fibrotic or sclerotic stroma. May show pseudoperineural invasion. May show apocrine metaplasia and atypia which is often seen with apocrine change. May be assoc with DCis, LCis and ADH! Myoepithelial markers p63 and SMM helpful to distinguish difficult cases that may look like carcinoma. May form a mass lesion (nodular sclerosing adenosis). Can sometimes be difficult to distinguish from tubular carcinoma. Tubular carcinoma tends to have more angulated glands compared to the lobulocentric architecture of SA and the stroma more desmoplastic than fibrous/sclerotic, also look for myoepithelial cells.

Radial scar

A central zone of fibroelastosis from which ducts and lobules radiate which  appear to dilate and expand centrifugally. Has a myoepithelial layer assess with p63 and SMM. Assoc with other benign alterations such as microcysts, apocrine metaplasia, UEH. May be assoc with ADH, LCis, Dcis. On mammography may show a stellate/spiculated mass with a radiolucent centre. x2 general risk of breast ca. If assoc with atypia, other lesions an increased risk of breast ca therefore some centres will excise fully if there is atypia.

Microglandular adenosis

A rare entity showing small round tubules infiltrating haphazardly within hypocellular stroma or fat. Lacks a myoepithelial layer but has a basement membrane (p63, SMM neg, laminin & collagenIV & reticulin positive around the glands).  Epithelial cells s100 pos and Er, PR neg. The glands are lined by a single layer of flat or cuboidal epithelium with a round nucleus and inconspicuous nucleolus. Has a open lumen which may contain eosinophilic PAS or mucicarmine positive material. Other entities – atypical MGA and carcinoma arising in MCA.


Breast Pathology. O’Malley, Pinder & Mulligan




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