Invasive carcinoma of the breast
About 90 % of breast carcinomas arise from tumor proliferation of the ductal epithelium. The rest have the origin in lobules. The term "in situ" refers to those tumors in which the tumor cells did not penetrate the basement membrane into the surrounding tissue.
At gross examination, the invasive carcinoma of the breast is a solid tumor, gray-whitish, usually with irregular borders infiltrating the adjacent adipose tissue. The consistency is firm to hard, due to the marked desmoplastic reaction sometimes with calcifications. Rarely, the tumor can be well circumscribed and have a softer consistency. The dimensions of the tumor range from 2 cm to 5 cm.
In advanced stages, one may observe the nipple retraction (due to the tumor infiltration of the lactiferous ducts), the "orange peel" aspect of the skin (due to lymphedema induced by tumor emboli in the lymphatics) and the immobility (fixation) of the tumor to the skin and / or profound structures (due to tumor infiltration of the pectoral muscles or deep fascia). When the tumor infiltrates the skin, ulceration may be present.
Invasive (infiltrating) carcinoma, NST (No Specific Type) of the breast is a malignant epithelial tumor resulted from proliferation of ductal epithelium of breast. It is the most common type of breast cancer (70 - 80 %). Atypical tumor cells form ribbons, tubules or nests, penetrate the basement membrane of the duct and infiltrate the surrounding tissue (fat tissue - Photo, skeletal muscle and/or skin), lymphatics, perineurial space. Frequently, tumor necrosis is seen. Tumor cells induce desmoplastic reaction in stroma (abundant fibrosis, collagen). (H&E, ob. x20)
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