There are several rare invasive breast cancers known as special type cancers. In some, cancer cells are characteristic and can be described as tubular, medullary (on the inside of the tissue), mucinous (starting in mucus cells), or cribriform (a distinctive pattern of holes).⁹

Another special type are angiosarcomas, soft-tissue cancers starting in cells in the walls of blood or lymph vessels. Although very rare, they can grow quickly and are difficult to treat. Primary angiosarcomas of the breast start in the breast, most often in women in their 30s and 40s. Secondary angiosarcomas of the breast, usually in older women, tend to stem from radiotherapy for previous breast cancer.^7,9

Other special type breast cancers include:^7,10

• adenoid cystic cancer – a slow growing cribriform cancer more usually diagnosed in salivary glands, but it can occur in breast tissue, and is less likely to spread
• metaplastic cancer – often an aggressive form, this is when ductal cells change into cells resembling soft tissue and connective tissue in the breast
• Non-Hodgkin lymphoma (NHL) of the breast – usually B-cell or T-cell lymphomas but sometimes associated with breast implants
• basal type cancers – producing high levels of some cytokeratins, proteins which normally help cells withstand mechanical stress
• papillary breast cancer – usually a ductal-type carcinoma in older women, which can be in situ or invasive, although many papillary tumours are benign.