Cytokeratin 19 immunolocalization in cell block preparation of thyroid aspirates. An adjunct to fine-needle aspiration diagnosis of papillary thyroid carcinoma.
BACKGROUND
Immunohistochemical staining for cytokeratin 19 (CK-19) is a useful ancillary technique for diagnosing papillary thyroid carcinoma (papillary carcinoma) in histologic specimens. Although similar results have been obtained on aspirate smears, to our knowledge the utility of CK-19 immunolocalization in cell block preparations as an adjunct to fine-needle aspiration diagnosis of papillary carcinoma has not been examined.


OBJECTIVE
The purpose of this study was to determine whether CK-19 immunostaining of cell block preparations of thyroid aspirates is a useful ancillary technique for diagnosing papillary carcinoma.


METHODS
Using a monoclonal antibody to CK-19 and a standard avidin-biotin complex technique, immunostaining was performed on paraffin-embedded cell blocks of 57 cases with the following cytologic diagnoses: (a) papillary carcinoma (20 cases); (b) atypical cytology, cannot exclude papillary carcinoma (19 cases); and (c) nonneoplastic thyroid (18 cases). The staining reaction in each case was graded on the basis of percentage of epithelial cells stained (1+, <10%; 2+, <10%-50%; 3+, >50). Tissue follow-up was available in all cases.


RESULTS
Nineteen (95%) of 20 cases with an unequivocal diagnosis of papillary carcinoma were positive for CK-19 (3+). Tissue follow-up confirmed papillary carcinoma in all 20 cases. Of the 19 cases with a diagnosis of atypical cytology, cannot exclude papillary carcinoma, 7 (37%) cases displayed 3+ immunostaining and subsequent excision confirmed papillary carcinoma in all 7 cases. The remaining 12 cases with 1+ immunostaining included surgically confirmed goiter (6 cases), adenoma (2 cases), lymphocytic thyroiditis (3 cases), and papillary carcinoma (1 case). The follicular cells in 18 cases with a cytologic diagnosis of nonneoplastic thyroid showed 1+ immunostaining. Histologic follow-up of these cases confirmed the nonneoplastic cytologic diagnoses.


CONCLUSIONS
Cytokeratin 19 immunostaining of cell block preparations of thyroid aspirates serves as a useful tool for the diagnosis of papillary carcinoma. Strong immunostaining (3+) for CK-19 aids in accurate diagnosis of malignancy in cytomorphologically equivocal cases of papillary carcinoma.
Khurana
Kamal K
KK
Department of Pathology, State University of New York Upstate Medical University Hospital, Syracuse 13210, USA. Khuranak@upstate.edu
Truong
Luan D
LD
LiVolsi
Virginia A
VA
Baloch
Zubair W
ZW
D001707:Biopsy, Needle; D002291:Carcinoma, Papillary / Q000175:diagnosis*; D003581:Cytodiagnosis / Q000379:methods / Q000706:statistics & numerical data; D004847:Epithelial Cells / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods / Q000706:statistics & numerical data; D007633:Keratins / Q000276:immunology / Q000378:metabolism*; D016612:Paraffin Embedding / Q000379:methods*; D012189:Retrospective Studies; D013194:Staining and Labeling / Q000379:methods; D013964:Thyroid Neoplasms / Q000737:chemistry / Q000175:diagnosis*; D016606:Thyroid Nodule / Q000737:chemistry / Q000473:pathology*; D016707:Tissue Fixation / Q000379:methods*
D007633:Keratins