title: Hamartoma of the breast: a clinicopathological review.
abstract: OBJECTIVE
  To review 25 cases of breast hamartoma and discuss the pathological criteria, and the usefulness of imaging modalities, fine needle aspiration cytology (FNAC), and needle core biopsy in the diagnosis.
  
  
  METHODS
  The hamartomas were assessed for interlobular fibrotic stroma, stromal adipose tissue content, pseudo-angiomatous stromal hyperplasia, and epithelial changes (hyperplasia, adenosis or apocrine metaplasia, and cyst formation). All imagings, previous FNACs, and biopsies were also reviewed.
  
  
  RESULTS
  Imaging (mammography, ultrasound, and magnetic resonance imaging) was performed in 18 cases, and mostly showed encapsulated masses with a heterogeneous appearance. Microscopically, all hamartomas demonstrated good demarcation with fibrous tissue condensation. Adipose tissue was noted in all cases (5-90%; mean, 31%), and interlobular fibrosis in 21 cases. Benign epithelial hyperplasia occurred in 10 cases, and pseudo-angiomatous stromal hyperplasia or cystic ducts in eight cases each. Apocrine metaplasia, calcification, stromal giant cells, and adenosis occurred in four cases or less. Two cases showed coexisting ductal carcinoma in situ limited to within the hamartoma. Needle core biopsies (four cases) and FNAC (14 cases) were largely insufficient, inconclusive, or non-specific.
  
  
  CONCLUSIONS
  Hamartomas do not possess specific diagnostic histological features. The role of FNAC and needle core biopsy in making the diagnosis is limited, and requires clinical and radiological correlation to avoid underdiagnosis.
authors.affiliation: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong SAR, China. garytse@cuhk.edu.hk
authors.forename: G M K
authors.initials: GM
authors.lastname: Tse
authors.forename: B K B
authors.initials: BK
authors.lastname: Law
authors.forename: T K F
authors.initials: TK
authors.lastname: Ma
authors.forename: A B W
authors.initials: AB
authors.lastname: Chan
authors.forename: L-M
authors.initials: LM
authors.lastname: Pang
authors.forename: W C W
authors.initials: WC
authors.lastname: Chu
authors.forename: H S
authors.initials: HS
authors.lastname: Cheung
mesh_terms: D000328:Adult; D000368:Aged; D001707:Biopsy, Needle / Q000379:methods; D001941:Breast Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006222:Hamartoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D008327:Mammography; D008875:Middle Aged; D012189:Retrospective Studies; D016217:Ultrasonography, Mammary