AbstractTo study the morphometric features of insular carcinoma (IC) of thyroid and follicular carcinoma (FC) in fine needle aspiration cytology (FNAC) smear to evaluate the role of the morphometric features to distinguish these two groups. We performed image morphometry in Hematoxyline and Eosin stained FNAC smears of eight each histopathology proven cases of IC and FC of thyroid. Nuclear area, diameter, perimeter, and standard deviation of nuclear area (SDNA) of these two groups were studied and compared. Nuclear area, diameter, perimeter, and SDNA of IC and FC were 30.43 μ2, 7.31 μ, 23.01 μ, 8.81 and 38.43 μ2, 7.66 μ, 25.63 μ, 10.83, respectively. Student's t‐test analysis did not show any significant difference (P > 0.05) in these two groups. Nuclear morphometry data indicate that the nuclear size and shape of IC and FC are essentially similar and it is not possible to differentiate these two entities with the help of image morphometric data. Diagn. Cytopathol. 2012. © 2011 Wiley Periodicals, Inc.