An In-Depth Evaluation of CD15 Expression in Thyroid Carcinoma: A Comprehensive Systematic Review

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Cluster of differentiation 15 (CD15) is a carbohydrate epitope involved in cell adhesion, migration, and tumor progression.
• CD15 expression varies across thyroid carcinoma (TC) subtypes, with uncertain diagnostic and prognostic implications due to inconsistent findings and methodological differences.

Purpose of the Study:

• To systematically review the prevalence, clinicopathologic associations, and diagnostic utility of CD15 expression in various thyroid carcinoma subtypes.
• Evaluate CD15's role in differentiating between different types of thyroid cancer.

Main Methods:

• A systematic literature search was conducted in May 2025 across major databases (PubMed, Scopus, Web of Science) following PRISMA guidelines.
• Sixteen observational studies encompassing 1665 thyroid carcinoma cases were included, with risk of bias assessed using the ROBINS-I tool.

Main Results:

• CD15 expression prevalence varied significantly across TC subtypes: highest in tall-cell papillary thyroid carcinoma (TCPTC) (71%-100%), moderate in classic papillary thyroid carcinoma (CPTC) (0%-100%), and lower in follicular variant papillary thyroid carcinoma (FVPTC) (17.6%-80%).
• Follicular thyroid carcinoma (FTC), medullary thyroid carcinoma (MTC), and anaplastic thyroid carcinoma (ATC) showed modest to low CD15 positivity.
• CD15 demonstrated high specificity (90%-100%) for papillary thyroid carcinoma (PTC), but sensitivity was inconsistent, especially in follicular-patterned variants.

Conclusions:

• CD15 is a highly specific marker for papillary thyroid carcinoma (PTC).
• Its variable sensitivity and expression patterns in follicular lesions limit its prognostic value as a standalone marker.
• CD15 may enhance diagnostic accuracy for thyroid cancer when incorporated into multiparametric immunohistochemical panels alongside other markers.