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Abstract: Thyroid cancer is the most common neoplasm of endocrine system. In Iraq thyroid cancer ranks the eighth among ten cancers in females.Therefore, it is a growing health problem.The present study was conducted to evaluate whether or not parvovirus B19 play a role in thyroid tumors and the correlation between the existence of virus and activation of NF - κB p65. Also this study extended to determine relevant cytokines (IL - 6, IL - 8, IL - 10 and IFN - α) in the microenvironment of thyroid tumors by using immunohistochemical technique.This study designed as a retrospective study. A total number of 94 formalin - fixed paraffine - embeded thyroid tumors tissue collected from archive of Histopathology Department of the Teaching Laboratories, Medical/ City, Al - Shaheed Ghazi Hospital Lab, Al - Kindy Hospital Lab, Alkarama Hospital Lab and Central Public Health Lab during the period July 2013 - November 2013. All samples are referred to the period between 2010 - 2013. Tissue blocks were divided into three groups. First group included 53 tissue block of malignant thyroid whereas second group included 41 tissue blocks of benign thyroid tumors and third group included 21 tissue blocks as control group were selected from the same benign cases which have normal tissue. From each block, seven sections of 4μm thickness were taken, one section was stained with Hematoxylin and Eosin (H&E) and the other six sections were immunohistochemically stained for human parvovirus B19, NF - κB p65, IL - 6, IL - 8, IL - 10 and IFN - α.The overall results of this study are described as follows : - The age of patients presented with malignant thyroid tumors ranged from 20 - 70 year with mean age 40±11.63 year while in benign tumors, the mean age was 37.6±11.19 year, ranged from (16 - 59) year.The papillary thyroid carcinoma was the most common type among malignant histopathological types 61%. In benign tumors the most common was follicular adenoma 29.3%.Human parvovirus B19 expression was higher in malignant tumors than in benign with no significant difference P=0.09 while it was significantly higher in malignant 66% and benign tumors 48.8% compared with their counterparts of control group 4.8%, p˂0.001.NF - κB p65 was positively expressed in all cases of malignant tumors 100% and 97.6% in cases of benign tumors compared with control group 23.8% with significant difference p˂0.001.IL - 6 expression was higher in benign than in malignant tumors with no significant difference p=0.22 while it was significantly higher in benign 90.2% and malignant tumors 81.1% compared with control group 52.4%, p=0.01 and p=0.03 respectively.Immunostaining reaction for IL - 8 was significantly higher in malignant tumors than that in benign 69.8% versus 31.7%, p˂0.001, while positive reaction was not detected in any tissue of control group.IL - 10 was expressed in 83% of malignant tumors, in 95.1% of benign tumors and 71.4% control group. The percentage of IFN - α positive was 83% in malignant tumors compared with 63% in benign tumors and normal tissue 52%. The difference was significant between malignant and benign tumors p=0.04 and between malignant and control group p=0.007.There was a significant correlation between human parvovirus B19 score category and IFN - α score r=0.296, p=0.031. But no significant correlation was noticed between B19 and the other cytokines.