The papillary patterned lesion of thyroid may be challenging with many diagnostic pitfalls. Tumor stromaplays an important part in the determination of the tumor phenotype. CD34 is thought to be involved in themodulation of cell adhesion and signal transduction as CD34(+) fibrocytes are potent antigen-presenting cells.Smooth muscle actin (SMA) positivity could be diagnostic for fibroblast activation during tumorigenesis. Weaimed to examine the expression of CD34 and alphaSMA in the stroma of papillary thyroid hyperplasia, papillarythyroid carcinoma and papillary tumors of uncertain malignant potential in order to elucidate their possibledifferential distribution and roles. A total number of 54 cases with papillary thyroid lesions were studied by routineH&E staining, CD34 and ASMA immunostaining. ASMA was not expressed in benign papillary hyperplasticlesions while it was expressed in papillary carcinoma, indicating that tumors have modulated stroma. Althoughthe stroma was not well developed in papillary lesions with equivocal features of uncertain potentiality, CD34was notable in such cases with higher incidence in malignant cases. So ASMA as well as CD34 could predictneoplastic behavior, pointing to the importance of the stromal role. Differences between groups suggest that thepresence of CD34 + stromal cells is an early event in carcinogensis and is associated with neoplasia, howeverASMA+ cells are more likely to be associated with malignant behavior and metastatic potential adding additionaltools to the light microscopic picture helping in diagnosis of problematic cases with H&E.