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Histiocytoid breast carcinoma: an enigmatic lobular entity
  1. Puay Hoon Tan1,
  2. Oi Harada1,
  3. Aye Aye Thike1,
  4. Gary Man-Kit Tse2
  1. 1Department of Pathology, Singapore General Hospital, Singapore, Singapore
  2. 2Department of Anatomical and Cellular Pathology, Chinese University of Hong Kong, Hong Kong, China
  1. Correspondence to Dr Puay Hoon Tan, Department of Pathology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore; tan.puay.hoon{at}


Histiocytoid breast carcinoma is an uncommon entity that is mostly regarded as a variant of lobular carcinoma. Its occurrence with apocrine lobular carcinoma in situ and consistent expression of gross cystic disease fluid protein 15 suggest apocrine differentiation. Its recognition is often challenging, particularly when histiocytoid tumour cells occur in a metastatic site before the primary diagnosis of breast carcinoma, or in limited core biopsy or cytology material. In the breast, its bland histological appearances can lead to a benign diagnosis. Clues to the correct conclusion include finding tumour cells with more cytological atypia, the presence of cytoplasmic vacuoles and secretions, coexistence with more traditional invasive lobular carcinoma patterns and/or lobular neoplasia, and the use of immuohistochemistry to confirm their epithelial nature. Close clinicoradiological correlation and awareness of histological mimics are needed to achieve an accurate diagnosis of this enigmatic condition that should be appropriately subsumed within the invasive lobular histological subtype.

  • Apocrine
  • benign mimics
  • breast pathology
  • cancer
  • histiocytoid
  • immunohistochemistry
  • lobular

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  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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