title: Histiocytoid breast carcinoma: an enigmatic lobular entity.
abstract: 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.
authors.affiliation: Department of Pathology, Singapore General Hospital, Singapore, Singapore. tan.puay.hoon@sgh.com.sg
authors.forename: Puay Hoon
authors.initials: PH
authors.lastname: Tan
authors.forename: Oi
authors.initials: O
authors.lastname: Harada
authors.forename: Aye Aye
authors.initials: AA
authors.lastname: Thike
authors.forename: Gary Man-Kit
authors.initials: GM
authors.lastname: Tse
mesh_terms: D001050:Apocrine Glands; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000473:pathology* / Q000556:secondary; D018275:Carcinoma, Lobular / Q000473:pathology*; D002352:Carrier Proteins / Q000378:metabolism; D003937:Diagnosis, Differential; D005218:Fat Necrosis / Q000473:pathology; D005260:Female; D006023:Glycoproteins / Q000378:metabolism; D016586:Granular Cell Tumor / Q000473:pathology; D015620:Histiocytic Disorders, Malignant / Q000473:pathology*; D015618:Histiocytosis, Sinus / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D026901:Membrane Transport Proteins; D008853:Microscopy / Q000379:methods; D025202:Molecular Diagnostic Techniques / Q000379:methods; D013544:Sweat Gland Neoplasms / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D002352:Carrier Proteins; D006023:Glycoproteins; D026901:Membrane Transport Proteins; C488892:PIP protein, human