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WHO Classification of Tumours
Ductal adenocarcinoma


Infiltrating ductal carcinoma, not otherwise specified (ductal NOS) accounts for the majority of invasive breast carcinomas. It arises from the mammary epithelium, most commonly from the epithelial cells of the terminal duct lobular unit (TDLU). Tumours can appear irregular and stellate or nodular. They typically lack sharp circumscription. On palpation, they are firm to hard. Tumour sizes range from <10mm to >10cm. Histologically, ductal NOS has no clear distinguishing characteristics. The neoplastic cells may form cords, clusters and trabeculae. Some tumours show a solid or syncytial infiltrative pattern with little associated stroma. Glandular differentiation is occasionally observed. The morphology of the tumour cells is also variable. They often contain abundant and eosinophilic cytoplasm. Nuclei may be regular or highly pleomorphic; mitoses may be virtually absent or extensive. The stromal component may consist of a scanty connective tissue element or a highly cellular fibroblastic proliferation. Marked hyalinisation may also be observed, as well as foci of elastosis or necrosis.
The incidence of ductal NOS tumours rises steeply with age. Women <40 years are rarely affected. Cases in men are exceptional. The highest incidence is observed in the affluent countries of North America, Europe and Australia, indicating an influence of environmental/lifestyle factors on breast cancer development. Risk factors include a diet high in calories and fat, alcohol consumption, early menarche, nulliparity, advanced age at first delivery, late menopause, sex steroids, exogenous hormones, and genetic susceptibility. Invasive breast carcinomas show a marked tendency to metastasize to distant sites. When they are detected at an early stage, the prognosis is very good

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Tavassoli FA, Devilee P (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Breast and Female Genital Organs.
3rd Edition
IARC Press: Lyon 2003