It is a prospective study done between 2010 to till date on 1123 thyroid lesions to estimate the incidence of medullary carcinoma of thyroid. Fine-needle aspiration (FNAC) was the initial diagnostic procedure to evaluate thyroid lesions. This study correlates FNAC cytology results with clinical, radiological and histopathological findings. Repeat FNAC and Ultrasound guided FNAC was done for inadequate samples and for difficult to palpate lesions. Medullary thyroid carcinoma is a hormone-producing malignant tumor that synthesizes calcitonin. MTC can be Sporadic or Familial. MTC is suspected after physical examination by measuring plasma calcitonin. For a positive diagnosis, histopathological confirmation is required. The extent of the tumor and the presence of metastatic spread are determined by using ultrasonography (USG), Computed tomography (CT) and Magnetic resonance imaging (MRI). A ims and objectives: To study the Incidence, cytological, histopathological and clinical correlation of medullary carcinoma of thyroid and to confirm the previous findings mentioned in the literature and to find any other additional findings from the histological and cytological view. To show the unique nature, rarity, and associations of medullary carcinoma. Marterials and methods: This study was conducted in the department of pathology in Mamata Academy of medical sciences Hyderabad and Mamata medical college. The material comprises of FNACs and thyroid specimens from Mamata General Hospital, Khammam and Mamata Academy of medical sciences from January 2010 to January 2020. Data was obtained from the surgical and pathology departments of Mamata General Hospital Khammam and Mamata Academy of Medical Sciences, Hyderabad Telangana. Routine Hematoxylin and Eosin, Pap stains were used to stain the smears and slides. For confirmation Congo red and calcitonin special stains were used and by checking baseline Calcitonin levels.