Cytokeratin 19 immunoreactivity in the diagnosis of papillary thyroid carcinoma: A note of caution

Sunati Sahoo, Syed A. Hoda, Juan Rosai, Ronald A. DeLellis

Research output: Contribution to journalArticlepeer-review

104 Scopus citations


To evaluate the expression of cytokeratin (CK) 19, we stained sections obtained from formalin-fixed, paraffin tissue blocks of 35 thyroid tumors (follicular adenoma [FA], 20; papillary thyroid carcinoma [PTC], 10 follicular variant [FV] and 5 usual type) and scored the extent of staining as follows: 1+ (<5% positively stained cells), 2+ (5%-25% positively stained cells), 3+ (25%-75% positively stained cells), and 4+ (> 75% positively stained cells). All 15 PTCs (including 10 FV-PTCs) were CK19 positive: 14 were 4+ and 1 (FV-PTC) was 2+. All 20 FAs also were CK19 positive: 15 were 1+, 1 was 2+, 4 were 3+, and none was 4+. In the FAs that were scored 1+, reactivity usually was confined to follicular cells lining cystically dilated atrophic follicles that lacked the typical nuclear features of PTC. The remaining FAs showed more diffuse reactivity, which was, however, less intense than that observed in the PTCs. Thus, immunoreactivity for CK19 is not specific for PTC, although we acknowledge that the extent and intensity of staining are considerably greater in this tumor than in FA. There were no significant differences in staining for CK19 between nonneoplastic follicles adjacent to PTCs and those adjacent to FAs.

Original languageEnglish (US)
Pages (from-to)696-702
Number of pages7
JournalAmerican journal of clinical pathology
Issue number5
StatePublished - 2001


  • Cytokeratin 19
  • Follicular adenoma
  • Immunohistochemistry
  • Papillary thyroid carcinoma

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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