Breast nonmalignant
Atypical hyperplasia
Atypical lobular hyperplasia

Topic Completed: 1 October 2014

Revised: 9 September 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Atypical lobular hyperplasia [title]

Jaya Ruth Asirvatham, M.B.B.S.
Julie M. Jorns, M.D.
Page views in 2018: 4,939
Page views in 2019 to date: 5,101
Cite this page: Asirvatham JR, Jorns JM. Atypical lobular hyperplasia. website. Accessed November 17th, 2019.
Definition / general
  • Also called lobular intraepithelial neoplasia 1 (LIN1)
Clinical features
  • Usually not associated with specific mammographic findings
    • Frequently associated with columnar cell lesions and flat epithelial atypia; less commonly associated with low grade invasive carcinomas which may have mammographically detectable calcifications, density or mass targeted on biopsy (Am J Surg Pathol 1998;22:1521, Am J Surg Pathol 2007;31:417)
  • Does not form a palpable mass
  • 19% develop invasive cancer at mean 15 years after diagnosis (4 - 5x usual risk), 42% are special subtypes with good prognosis (Cancer 2006;107:1227)
Radiology description
  • Incidental finding on core biopsy with no reliable radiological features
Prognostic factors
  • Lifelong followup is recommended
Gross description
  • Usually an incidental finding, not a palpable mass
Microscopic (histologic) description
  • Criteria of Page et al. (Schnitt: Biopsy Interpretation of the Breast, Second Edition, 2012):
    • Distends 50% or more acini within a lobule (so resembles LCIS) but not uniformly present throughout entire lobule OR
    • Involves all acini in a TDLU (so resembles LCIS) but does not distend the acini (i.e. caliber of the involved acini is similar to that of uninvolved acini)
  • May be no / minimal inflammatory response
  • Can involve ducts: alteration occurs around the duct as outpouchings producing a cloverleaf pattern
  • Lacks intracytoplasmic mucin
Microscopic (histologic) images

Scroll to see all images:

Contributed by Julie M. Jorns, M.D.

Absent E-cadherin
staining in

 Contributed by Dr. Mark R. Wick

Simple type

Atypical lobular hyperplasia

AFIP images

Loss of cell cohesion, disorderly
spread and pagetoid involvement
into normal acini (but < 50%
of acini involved)

Haphazardly dispersed
atypical cells (arrows)
have partially replaced
normal lobular cells

Cloverleaf pattern of
proliferation around terminal
duct with preservation of
normal epithelium centrally

Focal preservation of luminal spaces

Neoplastic cells occupy < 50% of acini

Expansion of acini on left side


Tumor cells with
loss of cohesion
have almost entirely
filled lumina


Ill defined
glandular proliferation
around terminal duct

Images hosted on other servers:

Atypical cells with focal preservation of luminal spaces

Involving sclerosing adenosis

Low power

Less regularly spaced cells

Pagetoid ductal involvement and cloverleaf pattern

Not all the lumen are obliterated (arrow)

Pleomorphic and cohesive cells

No surrounding inflammatory response

Variable appearance to cells

Involving a terminal duct lobular unit

Increase in glandular units

Monotonous cell population

Unusual clear cells and secretory features

ALH in fibroadenoma


Microglandular adenosis with adjacent ALH

Tubular adenoma with ALH

E-cadherin is focally negative

Cytology description
  • Loosely cohesive cell clusters composed of uniform cells with occasional intracytoplasmic lumina, minimal nuclear atypia but frequent eccentric nuclei
Positive stains
Negative stains
Electron microscopy description
  • Intracytoplasmic lumina, microvilli with secretory droplets; basement membrane and myoepithelial cells are present
Molecular / cytogenetics description
  • Diploid
Differential diagnosis
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