title: Invasive lobular carcinoma with extracellular mucin production and HER-2 overexpression: a case report and further case studies.
abstract: Invasive lobular carcinomas (ILC) of breast typically demonstrate intracytoplasmic mucin. We present a unique case of classical type ILC with abundant extracellular mucin and strong ERBB2 (HER2/neu) expression confirmed by immunohistochemistry and fluorescent in situ hybridization. Dual E-cadherin/p120 immunohistochemical stain demonstrated complete loss of membranous E-cadherin and the presence of diffuse cytoplasmic p120 staining, confirming the lobular phenotype. The tumor cells showed ductal-like cytoplasmic MUC1 staining, but were negative for MUC2 and other mucin gene markers. In addition, studies of tissue microarrays of 80 breast carcinomas with mucinous differentiation revealed 4 pure mucinous carcinomas showing significantly reduced E-cadherin staining without redistribution of p120 into cytoplasm. The findings suggest that the presence of extracellular mucin does not exclude a diagnosis of lobular carcinoma, and the morphologic and molecular characteristics of lobular and ductal carcinomas are more complex than previously appreciated.
authors.affiliation: Department of Pathology, Magee-Womens Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, USA. yuj@upmc.edu
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.forename: Rohit
authors.initials: R
authors.lastname: Bhargava
authors.forename: David J
authors.initials: DJ
authors.lastname: Dabbs
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000737:chemistry* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D000368:Aged; D015703:Antigens, CD; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics; D001706:Biopsy; D001943:Breast Neoplasms / Q000737:chemistry* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D015820:Cadherins / Q000032:analysis; D018275:Carcinoma, Lobular / Q000737:chemistry* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D051177:Catenins / Q000032:analysis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D015412:Mastectomy, Segmental; D018396:Mucin-1 / Q000032:analysis*; D009361:Neoplasm Invasiveness; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis* / Q000235:genetics; D046888:Tissue Array Analysis; D015854:Up-Regulation; D000095002:Delta Catenin
chemical_list: D015703:Antigens, CD; D014408:Biomarkers, Tumor; D015820:Cadherins; D051177:Catenins; D018396:Mucin-1; D018719:Erb-b2 Receptor Tyrosine Kinases; D000095002:Delta Catenin; C513384:CDH1 protein, human; C060192:MUC1 protein, human; C508053:ERBB2 protein, human