Cytokeratin 19 by IHC-12376 - Technical only, 12379 - Technical & interpretation

Test info

Cytokeratin 19 by IHC
12376 - Technical only, 12379 - Technical & interpretation
CK 19

All IHC stains will include a positive control tissue

  • CK 19 is useful in distinguishing papillary carcinoma (including follicular variant papillary carcinoma) from follicular adenoma, follicular carcinoma, and benign hyperplastic nodules
  • CK 19 usually stains papillary carcinomas in a strong, diffuse pattern
  • Normal thyroid parenchyma immediately adjacent to papillary carcinoma may also show strong to moderate reactivity
  • Normal thyroid farther from papillary carcinomas will show no reactivity or rarely focal, weak staining
  • One study3 reports CK 19 staining in follicular adenomas; in this study, 75% of follicular adenomas showed only scattered positive cells (usually confined to flattened cells lining cystic follicles)
  • Focal CK 19 staining has also been reported in areas of degeneration, usually at the site a previous FNA
  • Always correlate the immunohistochemical staining pattern with the histologic assessment including nuclear features
  • CK 19 also stains biliary epithelium including biliary carcinomas
  • CK19 is often co-expressed with CK7, and positive staining is often seen in lung carcinomas



Submit a formalin-fixed, paraffin-embedded tissue


Formalin-fixed, paraffin-embedded (FFPE) tissue block


FFPE tissue section mounted on a charged, unstained slide


Ambient (preferred)

  • Unlabeled/mislabeled block
  • Insufficient tissue
  • Slides broken beyond repair


AHL - Immunohistochemistry
Mo - Fr
1 - 2 days

Immunohistochemical staining and microscopic examination

Clinical and Interpretive info


If requested, an interpretive report will be provided



  • CK 19 is a low-molecular-weight keratin present in simple epithelial cells
  • CK 19 has been found to be present in papillary thyroid carcinoma, including follicular variants of papillary carcinoma
  • It is absent or only rarely focally present in normal thyroid

Staining pattern

  • Cytoplasmic


  1. Zubair WB et al: Differential expression of cytokeratins in follicular variant to papillary carcinoma: an immunohistochemical study and its diagnostic utility. Hum Pathol 30:1166-1171, 1999.
  2. Cheung CC et al: Immunohistochemical diagnosis of papillary thyroid carcinoma. Mod Pathol 2001;14(4):338-342.
  3. Sahoo S et al: Cytokeratin 19 immunoreactivity in the diagnosis of papillary thyroid carcinoma; a note of caution. Am J Clin Pathol 2001;116:696-702.


88342 - 1st stain
88341 - each additional stain