title: Immunohistochemical analysis based Ep-ICD subcellular localization index (ESLI) is a novel marker for metastatic papillary thyroid microcarcinoma.
abstract: BACKGROUND
  Thyroid cancer is among the fastest growing malignancies; almost fifty-percent of these rapidly increasing incidence tumors are less than or equal to 1cm in size, termed papillary thyroid microcarcinoma (PTMC). The management of PTMC remains a controversy due to differing natural history of these patients. Epithelial cell adhesion molecule (EpCAM) is comprised of an extracellular domain (EpEx), a single transmembrane domain and an intracellular domain (Ep-ICD). Our group reported nuclear Ep-ICD correlated with poor prognosis in thyroid cancer (Ralhan et al., BMC Cancer 2010,10:331). Here in, we hypothesized nuclear and cytoplasmic accumulation of Ep-ICD and loss of membranous EpEx may aid in distinguishing metastatic from non-metastatic PTMC, which is an important current clinical challenge. To test our hypothesis, Ep-ICD and EpEx expression levels were analyzed in PTMC and the staining was correlated with metastatic potential of these carcinomas.
  
  
  METHODS
  Thirty-six PTMC patients (tumor size 0.5 - 1cm; metastatic 8 cases and non-metastatic 28 cases) who underwent total thyroidectomy were selected. The metastatic group consisted of patients who developed lymph node or distant metastasis at diagnosis or during follow up. The patients' tissues were stained for Ep-ICD and EpEx using domain specific antibodies by immunohistochemistry and evaluated.
  
  
  RESULTS
  PTMC patients with metastasis had higher scores for nuclear and cytoplasmic Ep-ICD immunostaining than the patients without metastasis (1.96 ± 0.86 vs. 1.22 ± 0.45; p = 0.007 and 5.37 ± 0.33 vs. 4.72 ± 1.07; p = 0.016, respectively). Concomitantly, the former had lower scores for membrane EpEx than the non-metastatic group (4.64 ± 1.08 vs. 5.64 ± 1.51; p = 0.026). An index of aggressiveness, Ep-ICD subcellular localization index (ESLI), was defined as sum of the IHC scores for accumulation of nuclear and cytoplasmic Ep-ICD and loss of membranous EpEx; ESLI = [Ep - ICDnuc + Ep - ICDcyt + loss of membranous EpEx]. Notably, ESLI correlated significantly with lymph node metastasis in PTMC (p = 0.008).
  
  
  CONCLUSIONS
  Nuclear and cytoplasmic Ep-ICD expression and loss of membranous EpEx were found to correlate positively with metastasis in PTMC patients. In addition, ESLI had the potential to identify metastatic behavior in PTMC which could serve as a valuable tool for solving a current dilemma in clinical practice.
authors.affiliation: Alex and Simona Shnaider Laboratory in Molecular Oncology, Department of Pathology & Laboratory Medicine, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 60 Murray Street, Suite L6-304, Toronto, ON, M5T 3L9, Canada.
authors.forename: Tada
authors.initials: T
authors.lastname: Kunavisarut
authors.forename: Ipshita
authors.initials: I
authors.lastname: Kak
authors.forename: Christina
authors.initials: C
authors.lastname: Macmillan
authors.forename: Ranju
authors.initials: R
authors.lastname: Ralhan
authors.forename: Paul G
authors.initials: PG
authors.lastname: Walfish
mesh_terms: D000328:Adult; D000368:Aged; D000951:Antigens, Neoplasm / Q000378:metabolism*; D001665:Binding Sites; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002291:Carcinoma, Papillary / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003937:Diagnosis, Differential; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D011379:Prognosis; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000378:metabolism / Q000473:pathology; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule