[Diagnosis of the follicular variant of papillary thyroid carcinoma. Significance of immunohistochemistry].
OBJECTIVE
To study the expression of cytokeratin 19 (CK-19), HBME-1 and Ret in follicular-patterned thyroid tumors, and their significance for the diagnosis of the follicular variant of papillary thyroid carcinoma.


METHODS
111 well-differentiated follicular tumors were examined by immunohistochemistry: 59 papillary carcinomas (43 of the follicular variant), 40 follicular adenomas (among which 11 atypical adenomas), 10 oxyphil cell tumors and 2 follicular carcinomas.


RESULTS
CK-19 was diffusely expressed in all the papillary carcinomas, and was also expressed in 2/4 oxyphil cell carcinomas and 4/11 atypical adenomas. 90% of the follicular adenomas (26/29), the six oxyphil cell adenomas and the two follicular carcinomas showed at best a focal staining of dystrophic areas. 78% of the papillary carcinomas and 3/11 atypical adenomas were stained with HBME-1, whereas 26/29 adenomas (90%) and the 10 oxyphil cell tumors were negative. 34% of the papillary carcinomas expressed Ret (most of them were of the usual type (14/20)). The staining was often weak and focal (13/20). The other tumors were all negative for Ret.


CONCLUSIONS
CK-19 is a sensitive (100%) and specific (82.5%) marker of papillary carcinomas, which can be helpful in the diagnosis of its follicular variant. HBME-1 can improve this specificity when associated with CK-19. The Ret protein expression is of limited practical interest.
Guyétant
Serge
S
Service d'Anatomie Pathologique, Hôpital Trousseau, CHU, 37044 Tours Cedex 1. guyetant@med.univ-tours.fr
Michalak
Sophie
S
Valo
Isabelle
I
Saint-André
Jean-Paul
JP
D000236:Adenoma / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology; D018249:Adenoma, Oxyphilic / Q000175:diagnosis; D014408:Biomarkers, Tumor / Q000032:analysis*; D002291:Carcinoma, Papillary / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology; D018265:Carcinoma, Papillary, Follicular / Q000737:chemistry / Q000175:diagnosis* / Q000473:pathology; D003937:Diagnosis, Differential; D029721:Drosophila Proteins; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000032:analysis; D024862:Oxyphil Cells / Q000737:chemistry; D011518:Proto-Oncogene Proteins / Q000032:analysis; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis; D013964:Thyroid Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000473:pathology; D000951:Antigens, Neoplasm
D014408:Biomarkers, Tumor; D029721:Drosophila Proteins; D007633:Keratins; D011518:Proto-Oncogene Proteins; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C432845:HBME-1 antigen; D000951:Antigens, Neoplasm; C416649:Ret protein, Drosophila