title: Branched-chain in situ hybridization for κ and λ light chains: A powerful ancillary technique for determining B-cell clonality in cytology samples.
abstract: BACKGROUND
  Current immunohistochemical and in situ hybridization (ISH) assays are generally inconclusive for clonality unless plasmacytic differentiation is present. This study examined a series of cytology specimens and explored the ability of a branched-chain RNA (bRNA) ISH assay for immunoglobulin κ constant (IGKC) and immunoglobulin λ constant (IGLC) to detect a clonal population of B lymphocytes.
  
  
  METHODS
  Pathology databases were used to identify fine-needle aspiration biopsies (n = 28) and exfoliative cytology samples (n = 20). Demographic, flow cytometry, and excision biopsy results were recorded. bRNA ISH was performed on the Leica Bond platform with the following probes: IGKC, IGLC, immunoglobulin λ-like polypeptide 5 (IGLL5), and a housekeeping gene (HKG).
  
  
  RESULTS
  The bRNA ISH assay was validated with 30 surgical biopsies. On bRNA ISH, a clonal B-cell population (light-chain ratio > 10:1) was detected in 22 of 28 cases with a final diagnosis of lymphoma. In 2 cases, a κ predominance was present, although the ratio was <10:1. Eleven of the 17 κ-clonal lymphomas also expressed IGLL5, the latter recognized by the presence of an intranuclear signal. Two B-cell lymphomas lacked IGKC and IGLC, whereas 2 cases were negative for the HKG. In 12 of the 20 cases with reactive lymphoid tissue, bRNA ISH identified a polyclonal lymphoid population. No light-chain messenger RNA was detected in 6 cases (typically those associated with very few B cells).
  
  
  CONCLUSIONS
  The automated bRNA ISH platform is a robust technique for detecting a clonal B-cell population in cytology material.
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Kshitij
authors.initials: K
authors.lastname: Arora
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Ivan
authors.initials: I
authors.lastname: Chebib
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Zukerberg
authors.affiliation: Affymetrix, Santa Clara, California.
authors.forename: Manoj
authors.initials: M
authors.lastname: Gandhi
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Miguel
authors.initials: M
authors.lastname: Rivera
authors.affiliation: Division of Oncology, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: David
authors.initials: D
authors.lastname: Ting
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Vikram
authors.initials: V
authors.lastname: Deshpande
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001402:B-Lymphocytes / Q000473:pathology*; D044963:Biopsy, Fine-Needle; D005260:Female; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D007146:Immunoglobulin lambda-Chains / Q000235:genetics*; D017403:In Situ Hybridization / Q000379:methods*; D008197:Lymph Node Excision; D016393:Lymphoma, B-Cell / Q000473:pathology*; D008297:Male; D008875:Middle Aged
chemical_list: D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains
keywords: B-cell lymphoma; immunoglobulin κ constant (IGKC); immunoglobulin λ constant (IGLC); immunoglobulin λ-like polypeptide 5 (IGLL5); in situ hybridization (ISH)