AbstractBackground: Leptin is a multifunctional adipose regulatorypeptide that has various actions in carcinogenesis. Mammarycarcinoma is one of the leading cancers in the world withtempted aspects to explore new prognostic factors.Aim of Study: We attempted to leptin expression in mam-mary carcinoma and its clinicopathological correlation.Material and Methods: Thirty-five cases of breast carci-nomas were studied for correlating leptin immunohistochemicalexpression with other available parameters.Results: The included cases' mean age is 57 years ±SD11.7. The majority of cases were invasive duct carcinoma. Asregards clinical pathological stages, stage IA (48.6%), stage IB (14.3%), stage IIA (14.3%), stage IIIA (2.9%), stage IIIB (14.3%), and finally stage IIIC (5.7%). Leptin immunostain was positive in 60% of studied mammary carcinoma cases and negative in 40%. Five cases of peri-tumoral fibrocystic disease were studied; all showed leptin positivity in ductal cells. Correlating leptin immunohistochemistry results with other findings, we found that significant relationship was found between leptin staining and mammary carcinoma histopathological type. Most invasive duct carcinoma (NST) showed positive leptin immunostaining (67.9%). On the other hand, most cases of the other types (lobular and mixed carcinomas) showed negative staining (71.4%) (p-value 0.027). Leptin immunostaing had insignificant correlation to T stage, grade, tumor lymphovascular emboli and perineural infiltration. As regarding tumor lymph nodal metastasis, most of cases without nodal metastasis (N0) were leptin-positive (76.5%) with significant p-value of 0.025. A significant relationship was detected between leptin immunostaining and clinicopathologic staging as well as molecular subtype. Estrogen-positive cases significantly correlate with leptin, with p-value of 0.0001. This also was observed with progesterone positivity, with p-value of 0.002. No significant relationship was found between leptin and Her-2 as well as Ki-67.Conclusion: Leptin immunostain can be of an extremehelp in mammary carcinoma prognosis.