The vast majority of breast cancers arise from epithelial cells lining the terminal duct lobular unit (Figures 7.1,7.2,7.3,7.4,7.5). Some tumours do show distinct patterns of growth and cellular morphology, and on this basis certain types of breast cancer can be identified. Those with specific features are called invasive carcinomas of special type, while the remainder are con sidered to be of no special type. This classification has clinical relevance in that certain special type tumours have a much better prognosis than tumours that are of no special type.
Invasive breast carcinoma of no special type. Infiltrating nests of carcinoma cells. Note two small stromal microcalcifications (arrows). These are often detected on mammograms.
Invasive classical pattern lobular carcinoma. Note single files of tumour cells, some of which show cytoplasmic vacuolation (arrows). H&E, original magnification x20.
Invasive mucinous carcinoma. One of the 'special types' of carcinoma. Note islands of tumour cells set in a background of mucoid material which stains a pale bluishpink with H&E. These tumours have a better prognosis than no special type and lobular carcinomas. H&E, original magnification x10 and x40 (insert).
Invasive lobular carcinoma. A: Note stromal infiltration by cords of small carcinoma cells showing a single file pattern. E-cadherin staining. B: A number of small normal ducts show strong positive staining of epithelial cells, while the invasive carcinoma cells are completely negative.
Tubular carcinoma (A). Infiltration of stroma by well-differentiated carcinoma. By definition, a tubular carcinoma must show >90% tubules when assessing its architecture. CK 5/6 staining of the same case (B). Note occasional normal ducts showing an intact myoepithelial layer with strong positive immunostaining. The invasive carcinoma lacks a myoepithelial layer and shows no staining.
Approximately 80% of breast cancers are of no special type. Lobular cancers account for around 10% of all invasive cancers. These are often more difficult to diagnose and their size is often underestimated ...