Mammography and breast ultrasound are the modalities primarily used to screen for breast cancer. Mammography is highly sensitive and can identify 80-90% of patients with breast cancer.
Unfortunately, a positive mammographic finding does not always equate with malignancy. Only between 2 to 4 of 10 patients with abnormal mammograms are found to have breast cancer at histologic analysis. Additionally, about 10% of breast cancers cannot be identified mammographically even when they are palpable. Invasive lobular carcinoma can be difficult to identify mammographically because of its diffuse growth pattern and tendency to have an opacity equal to or less than the surrounding parenchyma. Ultrasound can permit rapid differentiation of cystic and solid lesions, but accurate differentiation between benign and malignant solid lesions is sometimes difficult.
Invasive ductal carcinoma is the most common type of breast cancer (70-80% of cases), while invasive lobular carcinoma is relatively uncommon (5-10% of cases). Breast cancers display a considerable variation in FDG uptake. Invasive ductal carcinoma exhibits significantly higher FDG uptake compared to invasive lobular carcinoma. Focal nodular lesions also show higher accumulation when compared to infiltrative/diffuse lesions. Additionally, the greater the degree of tumor proliferation and the greater the degree of tumor dedifferentiation, the greater the FDG accumulation. The estrogen and progesterone status of a lesion do not appear to influence FDG uptake. Multiple other factors influence uptake of FDG in breast cancer cells including the microvasculature for delivering nutrients, Glut-1 surface receptors for transport of FDG into the cell, hexokinase levels for entering FDG into glycolysis, the proliferation rate of the tumor, and the level of hypoxia-inducible factor-1-alfa for up-regulating Glut-1 receptors.
Triple-negative breast cancer accounts for 15% of invasive breast cancers and is characterized by the lack of estrogen and progesterone receptors and the absence of HER2 over expression (it is therefore unresponsive to the usual endocrine therapies). It has a more aggressive clinical course than other forms of breast cancer and patients with triple negative breast cancer have a relatively poor outcome with a higher relapse rate. Patients with triple-negative breast cancer also have a high early incidence of brain metastases. However, patients that have a complete pathologic response to neoadjuvant therapy have a good prognosis with a 3 year overall survival of 94% (compared to 68% for patients with residual tumor at the time of surgery). Premenopausal African American women have a higher risk of developing triple receptor negative breast cancer. Also- women with the BRCA1 mutation are reported to develop breast cancer at an early age with a high prevalence of triple receptor negative cancers.
Inflammatory breast cancer is a rare (1-2% of primary breast cancers), but aggressive, rapidly proliferating form of breast cancer. The criteria for the clinical diagnosis includes erythema, edema involving more than 2/3s of the breast, peau d orange changes, breast enlargement, warmth, tenderness, and breast induration on palpation. About 20% of patients with IBC have distant metastases at the time of diagnosis. The standard treatment is neoadjuvant chemotherapy followed by modified radical mastectomy and subsequent radiation therapy. The mean 5 year survival following multidisciplinary therapy is 20-40%, with a median survival of 12-36 months.