Breast nonmalignant
Benign tumors / changes
Hamartoma of breast

Author: Monika Roychowdhury, M.D. (see Authors page)
Editorial Board Member Review: Emily S. Reisenbichler, M.D.

Revised: 30 October 2017, last major update October 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Hamartoma [title] breast [title]

Cite this page: Roychowdhury, M. Hamartoma of breast. PathologyOutlines.com website. http://pathologyoutlines.com/topic/breasthamartoma.html. Accessed December 14th, 2017.
Definition / general
  • Well circumscribed, often encapsulated mass composed of all components of breast tissue
Essential features
  • Uncommon breast tumor that contains normal breast parenchyma including fibrous, fibrocystic and adipose tissue
  • Clinically presents as painless, soft to firm lump or asymmetry
  • Excision with negative margins is curative
  • Microscopy shows well circumscribed mass with normal breast components (eg. terminal ductal lobular unit, adipose tissue and hyalinized stroma)
Terminology
  • Initially defined as mastoma (Beitr Pathol Anat 1928;81:1)
  • Arrigoni et al. first used the term hamartoma in 1971 (Surg Gynecol Obstet 1971;133:577)
  • Also called fibroadenolipoma, adenolipoma
Epidemiology
  • Uncommon, ~5% of all benign breast masses
  • Mean age 45 years
  • Rare in teenagers (Breast J 2009;15:515)
Etiology
  • May be a malformation, not a neoplasm
Clinical features
  • Presents as painless, soft to firm breast lump or asymmetry
Radiology description
  • Xray: clearly demarcated lesion on mammography
  • Ultrasound: heterogeneous appearance with varying internal echotexture and absent retrotumor acoustic phenomenon
Radiology images

Images hosted on PathOut server:

Images contributed by Dr. Mark R. Wick

Mammogram shows
asymmetrical lesion

Prognostic factors
  • Same malignant potential as normal breast tissue, although may have coexisting DCIS (J Clin Path 2002;55:541) or invasive ductal carcinoma, which is likely coincidental
Case reports
Treatment
  • Excision; does not recur if negative margins
Gross description
  • Well circumscribed mass of firm, rubbery, white tissue, 1 - 8 cm, more distinctive grossly than microscopically
Gross images

Images hosted on PathOut server:

Ovoid yellow white mass



Images hosted on other servers:

Various images

Fat, glandular elements and stroma in pregnant patient

Smooth and glistening mass

Microscopic (histologic) description
  • Sharply circumscribed mass of disordered breast ducts and lobules
  • Ducts often dilated, accompanied by fibrosis
  • May have smooth muscle, adipose tissue, hyaline cartilage, pseudoangiomatous hyperplasia
  • May resemble gynecomastia due to lack of ducts
  • Myoid hamartoma: also has smooth muscle stroma; may contain epithelioid cells (Arch Pathol Lab Med 1996;120:676, Hum Pathol 1985;16:212)
Microscopic (histologic) images

Images hosted on PathOut server:

With ductal hyperplasia resembling gynecomastia

Smooth muscle bundles (arrows) and fibrous tissue

Hyaline cartilage and adipose tissue

Well defined fibrous tumor,
ducts separated by
connective tissue

Adipose tissue and ducts resembling gynecomastia

Disordered ducts and
lobules, contributed
by Dr. Mark Wick



Images hosted on other servers:
Missing Image

Mass with normal terminal ductal lobuler unit

Missing Image

Myoid Hamartoma

Missing Image

Fig 3 - Adipose tissue and lobules without atypia


Dilated ducts and fibrous stroma

Breast ducts and adipose tissue (adenolipoma)

Epithelial and mesenchymal components

Rounded border and fibrous capsule

Adipose normal lobules, cystically dilated ducts


Various images

With LCIS and invasive lobular carcinoma


Myoid hamartoma: H&E and smooth muscle actin+

Cytology description
  • Moderately cellular, sheets of bland ductal cells and lobular units, bipolar stromal nuclei, varying amounts of adipose tissue, less prominent stromal fragments, occasional apocrine and foamy cells, no atypia
  • Findings are not specific (Cancer 2003;99:255, Cytopathology 2003;14:195)
Differential diagnosis
Board review question #1
    A 45 year old woman presents with an irregular symmetry in her right breast. Ultrasound guided core biopsy showed normal breast tissue components. The radiologist was sure that the lesion was biopsied. What is the most likely possibility?

  1. Breast hamartoma
  2. Breast lipoma
  3. Edge of a fibroadenoma
  4. Radiologist missed the lesion
Board review answer #1
A. Breast hamartoma

The asymmetric lesion by imaging and the histologic finding of normal breast components supports this diagnosis. Also, since the radiologist was sure the lesion was biopsied, the possibility that the lesion was missed is excluded.