title: Performance characteristics of mucinous (colloid) carcinoma of the breast in fine-needle aspirates: observations from the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytopathology.
abstract: BACKGROUND
  Mucinous breast carcinoma has characteristic cytologic features, but few studies exist that analyze the reproducibility of this diagnosis.
  
  
  OBJECTIVE
  To analyze participants' diagnosis of mucinous carcinoma in breast fine-needle aspiration (FNA) slides distributed in an educational interlaboratory peer comparison program.
  
  
  METHODS
  Participant responses for FNA slides with a reference diagnosis of mucinous carcinoma, distributed between 2001-2008 in the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytopathology, were evaluated for concordance with the general category and reference diagnosis of mucinous carcinoma.
  
  
  RESULTS
  Of 8061 responses, 6353 (78.8%) were categorized as malignant; 775 (9.6%) as suspicious; and 933 (11.6%) as negative. The most frequent incorrect responses for the benign category included fibroadenoma (51.7%), nonspecified benign lesion (12%), fibrocystic changes (7.8%), and fat necrosis/granulomatosis/foreign body reaction (6.9%). Conventional Papanicolaou-stained preparations were reviewed for 58.7% (4732) of responses; of these, 39.4% (3177) were from modified Giemsa-stained smears and 1.9% (152) from ThinPrep slides. Papanicolaou-stained conventional smears had the lowest concordance (86.5%) when compared to modified Giemsa-stained smears (91.2%) and ThinPrep challenges (92.1%) (P < .001). Participants specifically diagnosed mucinous carcinoma 37.3% of the time, and modified Giemsa-stained challenges performed best (43.1%, P < .001). There was no significant difference between cytotechnologists' and pathologists' responses (87.9% versus 88.2%; P  =  .69).
  
  
  CONCLUSIONS
  Mucinous carcinoma in FNA was not accurately identified in a glass slide interlaboratory comparison program. We observed better performance with modified Giemsa-stained and ThinPrep slides than with Papanicolaou-stained preparations. The most common response for the benign category of mucinous carcinoma was fibroadenoma. Increased awareness of the cytologic features of mucinous carcinoma may improve accuracy in breast FNA.
authors: Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA. rodolfol@bcm.edu
authors: Rodolfo
authors: R
authors: Laucirica
authors: Joel S
authors: JS
authors: Bentz
authors: Walid E
authors: WE
authors: Khalbuss
authors: Amy C
authors: AC
authors: Clayton
authors: Rhona J
authors: RJ
authors: Souers
authors: Ann T
authors: AT
authors: Moriarty
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000175:diagnosis*; D044963:Biopsy, Fine-Needle; D001943:Breast Neoplasms / Q000175:diagnosis*; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D015588:Observer Variation; D010338:Pathology, Clinical; D010380:Peer Review; D015203:Reproducibility of Results; D012955:Societies, Medical; D013194:Staining and Labeling; D014481:United States