ÖZET Giriş: Genç yaşta tespit edilen meme kanseri insidansı artmakta olup bu hastalarda mortalite yüksek seyretmektedir. Çalışmamızın amacı kırk yas altı kadınlarda görülen meme kanseri hastalarının klinik, histopatolojik ve operatif ozelliklerini belirlemek. Materyel ve metod: 2013 ile 2017 tarihleri arasında 40 yaş altında olup meme kanseri tanısı konulmuş hastaların klinikopatolojik ve operatif özellikleri değerlendirildi. Bulgular: 103 hastamız olduğunu tespit ettik. Ortalama yaş 35.4 (3.8) olarak tespit edildi. Hastalarımızın %13.4’ üne evre 1, %57.2’sine evre 2, %22.3’ü evre 3, %6.7’si tanı anında uzak metastazı olduğu için evre 4 olarak tespit edildi. %22.3 T1, %48.5 T2, %23.3 T3, %2.9 T4 olarak tespit edildi. Tümörlerin ortalama çapını 2.1 cm (±1.3) olarak belirledik. %37.8 luminal A, %35.9 luminal B, %20.3 tripple negatif ve HER 2 pozitifliğini %21.3 olarak tespit edildi. %55.3 hastaya modifiye radikal mastektomi, %39.8 hastaya segmenter mastektomi yapıldı. 76 (%73.7) hasta da aksillar lenf nodalarında metastaz saptandı. Sonuç: Genç yaşta tespit edilen meme kanseri hastalarını özellikli hasta grubu olarak değerlendirip tedavi protokollerini buna göre belirlemekte fayda olduğunu düşünüyoruz. Anahtar kelimeler: Genç yaş meme kanseri; Tümör histolojisi; Tedavi ABSTRACT Background: The incidence of breast cancer detected at a young age is increasing in the modern age and mortality is also observed to be high in these types of patients. The aim of this study is to determine the clinical, histopathological and operative characteristics of breast cancer patients under 40 years of age. Materials and Methods: In this study, clinicopathologic and operative characteristics of patients under the age of 40, who were diagnosed with breast cancer between the years of 2013 and 2017, were evaluated. Results: We identified 103 patients for the study. The mean age was determined to be 35.4 (3.8). 13.4% of our patients were observed to be at Stage 1, 57.2% were at stage 2, 22.3% were at stage 3, and 6.7% were found to have Stage 4 Cancer due to distant metastasis at the time of the diagnosis. 22.3% were identified as T1, 48.5% as T2, 23.3% as T3, and 2.9% were identified as T4. The mean diameter of the tumors was 2.1 cm (± 1.3). It was determined that 37.8% were luminal A, 35.9% were luminal B, 20.3% were triple negative and HER 2 positivity was found to be 21.3%. Modified radical mastectomy was performed in 55.3% of the patients and segmental mastectomy was performed in 39.8% of the patients. 76 (73.7%) patients were found to have metastasis in their axillary lymph nodes. Conclusion:We think it is useful to evaluate and treat breast cancer patients diagnosed at young age as a special patient group and thus we recommend determining the treatment protocols accordingly. Keywords: Young women breast cancer; Tumor histology; Treatment