title: Immunohistochemistry differentiates papillary thyroid carcinoma arising in ectopic thyroid tissue from secondary lymph node metastases.
abstract: OBJECTIVE
  To verify whether immunohistochemistry might be useful in the distinction between a true laterocervical metastasis of an undetected thyroid carcinoma and a primary tumor outside the gland.
  
  
  METHODS
  Galectin-3, cytokeratin 19, and HBME-1 were assessed in six cases (group A) of laterocervical masses harboring papillary thyroid carcinoma (PTC) but without a thyroid tumor, and in eight cases (group B) showing PTC both in the thyroid and in the laterocervical masses. In both groups, normal-looking follicles adjacent to the laterocervical neoplasia were present.
  
  
  RESULTS
  We found that the apparently normal follicles in group A were negative for all the antibodies, while group B showed strong and diffuse positive immunostaining. The neoplastic areas were always positive for all the antibodies in both groups.
  
  
  CONCLUSIONS
  Even if immunohistochemical patterns of residual follicles of group B are very well differentiated that they resemble normal thyroid parenchyma, they may well be metastatic carcinomas. On the contrary, the presence of morphologically and immunohistochemically normal-looking follicles in group A, with no intrathyroid tumor, suggests that the primary PTC might possibly develop in the ectopic thyroid tissue. In cases showing morphologically and immunohistochemically normal-looking follicles in laterocervical masses, these findings might lead to a reduction of the overdiagnosis of metastatic disease of an undetected carcinoma.
authors: Human Pathology Department, University School of Medicine, Via del Vespro, Palermo, Italy. cabibidaniela@virgilio.it
authors: Daniela
authors: D
authors: Cabibi
authors: Matilde
authors: M
authors: Cacciatore
authors: Carla
authors: C
authors: Guarnotta
authors: Federico
authors: F
authors: Aragona
mesh_terms: D000368:Aged; D002291:Carcinoma, Papillary / Q000473:pathology* / Q000601:surgery; D002828:Choristoma / Q000473:pathology / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D006042:Goiter / Q000473:pathology; D050031:Hashimoto Disease / Q000473:pathology; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D013961:Thyroid Gland / Q000473:pathology; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000556:secondary / Q000601:surgery; D013965:Thyroidectomy; D013966:Thyroiditis / Q000473:pathology