Answer:
Noninvasive malignancies
DCIS or intraductal carcinoma arises in terminal mammary ducts as a proliferation of malignant epithelium within the basement membrane. Center of lesion often undergoes necrosis and can calcify. A palpable mass can be produced if multiple ducts are involved. The chance of occult invasion increases with tumor size and comedo type. Treatment options include lumpectomy, lumpectomy with radiation or total mastectomy. Depends on presence of occult invasive disease, multicentricity, and disease in other breast.
LCIS (lobular carcinoma in situ) is characterized by abnormal proliferation of cells confined to the lobules and occasionally filling the distal ducts. It is clinically silent, never forms a palpable mass, does not readily produce microcalfications, and is often found incidentally, mainly in premenopausal women. LCIS is multifocal in the breast in which it is found and is present in both breasts in most women. It is a marker for future malignancy, with a 25% risk of developing invasive carcinoma. Half of future cancers will be invasive lobular and half will be invasive ductal cancers. With LCIS in particular, bilateral mastectomy with immediate reconstruction should be considered given the long term risk of invasive disease.
Invasive malignancies
INFILTRATING DUCTAL CARCINOMA: Arises from the duct epithelium; the most common type (70% of invasive breast cancers). Infiltrates into the surrounding stroma. Stromal reaction may be intense. Presents as a mass or density on mammogram.
INVASIVE LOBULAR CARCINOMA: Much less common (3-10%). Occurs primarily in the upper outer quadrant of the breast. Small round cells infiltrate stroma "Indian file" fashion.
LESS COMMON VARIANTS:
Generally have better prognosis because well differentiated.
Medullary - accounts for 5% of invasive breast cancers. Bizarre anaplastic tumor cells with lymphatic infiltration.
Mucinous - Large amount of extracellular mucin, favorable prognosis.
Tubular - An early well-differentiated form of invasive duct cancer in which the malignant cells form regular and orderly tubules but resemble normal ducts. Calcification is common. May represent an early stage in the progression from premalignant to invasive duct carcinoma. Excellent prognosis.
Mixed connective tissue tumors
PHYLLODES TUMOR (CYSTOSARCOMA PHYLLODES): Histologically similar to fibroadenoma with a large component of connective tissue stroma interspersed with layers of benign epithelial cells. The epithelial clefts enlarge into cystic stuctures and spread into leaflike patterns - "phyllodes." Benign in majority. Usually present in 40's with large tumor (4-5cm). Treatment is wide local excision if benign histology or total mastectomy for malignant appearing lesions.
ANGIOSARCOMA: Exceedingly malignant, numerous dilated vascular channels; rarely metastasize to nodes, usually hematogenous spread. Treatment is total mastectomy; survival depends on histologic grade.