title: Invasive Duct Carcinoma of the Breast With Dominant Signet-Ring Cell Differentiation: A Microsatellite Stable Tumor With Aggressive Behavior.
abstract: OBJECTIVE
  Invasive duct carcinoma, no special type (IDC, NST), of the breast with signet-ring cell differentiation is uncommon. This study was undertaken to describe the clinicopathologic characteristics of IDC, NST, with dominant signet-ring cell differentiation, and look for microsatellite instability in these tumors.
  
  
  METHODS
  Cases of IDC, NST, with dominant signet-ring cell differentiation, diagnosed over the past 2 years, were retrieved. Detailed clinical and pathologic analyses were performed. Immunohistochemistry was performed for estrogen receptor, progesterone receptors, Her-2 neu, Ki-67, E-cadherin, CK7, and CK20. Microsatellite instability was examined using immunohistochemistry for the 4 mismatch repair proteins: MLH1, MSH2, MSH6, and PMS2.
  
  
  RESULTS
  Of the total 1646 cases of IDC, NST, only 5 cases showed dominant signet-ring cells (ranging from 70% to 100%) and strong E-cadherin positivity and were diagnosed as IDC, NST, with dominant signet-ring cell differentiation. The age ranged from 32 to 65 years. Two cases were of histologic grade 3 and the remaining cases were grade 2 tumors. Four patients had T2 tumor and 1 had T3 tumor. All cases had axillary lymph node metastasis and distant metastasis was present in 1 case. All cases were microsatellite stable.
  
  
  CONCLUSIONS
  Signet-ring cell differentiation in IDC, NST, is rare and associated with a high histologic grade. Lymph node metastasis and distant metastasis are common, indicating an aggressive clinical behavior. Thus, they should be recognized separately as they may warrant aggressive management. However, these are microsatellite-stable tumors in contrast to signet-ring cell tumors of other organs.
authors.affiliation: Departments of *Histopathology †General Surgery ‡Nuclear Medicine, Post Graduate Institute of Medical Education & Research (PGIMER), Chandigarh, India.
authors.forename: Debajyoti
authors.initials: D
authors.lastname: Chatterjee
authors.forename: Amanjit
authors.initials: A
authors.lastname: Bal
authors.forename: Ashim
authors.initials: A
authors.lastname: Das
authors.forename: Pavneet S
authors.initials: PS
authors.lastname: Kohli
authors.forename: Gurpreet
authors.initials: G
authors.lastname: Singh
authors.forename: Bhagwant Rai
authors.initials: BR
authors.lastname: Mittal
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis*; D018270:Carcinoma, Ductal, Breast / Q000175:diagnosis*; D018279:Carcinoma, Signet Ring Cell / Q000175:diagnosis* / Q000473:pathology; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D051718:MutS Homolog 2 Protein / Q000235:genetics; D011379:Prognosis
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein