Introduction & Objective: Thyroid cancer affects individuals of any gender and age. Also, its various pathologies have different prognoses and responses to different treatments in addition to age and gender-specific distribution. Therefore, this study was conducted with the aim of investigating the frequency of histopathology of surgically operated malignant thyroid masses and its relationship with age and gender. Materials & Methods: This cross-sectional study was conducted on patients with malignant thyroid masses who underwent surgery at Imam Khomeini Hospital in Tehran between 1991 and 1996. Patients who were diagnosed with malignant thyroid lesions according to the pathology report were included in the study. Also, patients with a history of surgery, previous thyroid malignancy, and incomplete medical information were excluded from the study. Finally, the clinical symptoms, age, and gender of the patients were collected and recorded along with the frequency of the type of thyroid histopathology. Results: In this study, 75 patients (46 women and 29 men) were included in the study. Most of the patients (26%) were 60 years and older and only two patients were under 20 years old. The most common symptoms were neck mass, dysphagia, dysphonia, shortness of breath, and weight loss, respectively. Papillary carcinoma was the most common (55%) and metastasis was the least (7%) histopathology of malignant thyroid masses. Conclusions: The present study showed that in line with previous studies, the prevalence of thyroid cancer is higher in women and the elderly. Also, papillary carcinoma is the most common pathology of malignant thyroid masses.