Breast - nonmalignant
Adenosis of breast - general

Author: Jaya Ruth Asirvatham, M.B.B.S., M.D. (see Authors page)
Editor: Julie M. Jorns, M.D.

Revised: 17 August 2018, last major update February 2015

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Adenosis [title] breast [title]

Cite this page: Asirvatham, J.R. Adenosis of breast - general. website. Accessed October 19th, 2018.
Definition / general
  • Any hyperplastic process (see subtypes below) primarily involving glands (i.e. an increased number of glandular components)
  • Common, benign, often accompanied by fibrosis
  • Premenopausal: lesions with predominant epithelial component (proliferation of acini and ducts); nodular adenosis
  • Postmenopausal: lesions with more sclerosis (sclerosing adenosis)
  • Not specific
  • Part of fibrocystic changes
Clinical features
  • Can present as a mass (as nodular adenosis or adenosis tumor) or as calcifications on imaging
Prognostic factors
  • With some types (sclerosing adenosis), the risk of subsequent breast cancer is 1.5 - 2x higher
  • Does not require treatment if there is no cytologic atypia
Microscopic (histologic) description
  • See also separate topics for each subtype
  • Apocrine adenosis: adenosis with predominant apocrine cytology
  • Microglandular adenosis: nonlobulocentric proliferation of mammary glands with an infiltrative pattern, lined by a single epithelial layer with a basement membrane
  • Sclerosing adenosis: lobulocentric proliferation of glands (2 layers) with glandular compression and distortion due to stromal proliferation
  • Simple adenosis: loosely structured proliferation of acinar or tubular structures, with epithelial and myoepithelial layers, surrounded by basement membrane, without distortion of lobular architecture
  • Tubular adenosis: haphazard proliferation of branching tubules (2 layers)
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Dr. Mark R. Wick:

Blunt ductal

Columnar cell change

Nodular / sclerosing


AFIP images:

Reticulin stain,
continuous basement
around glands

Images hosted on other servers:

Low power, somewhat lobular architecture

Enlarged lobules

Epithelial and myoepithelial cells

Adenosis with columnar cell change

Differential diagnosis
  • Invasive carcinoma: mainly an issue in cases of sclerosing, tubular and microglandular adenosis