Molecular profiling has led to classification of breast cancer into the following five distinct subtypes:[17,18]
- Luminal A.
- Luminal B.
The use of molecular profiling in breast cancer includes the following:[17,18]
- ER and PR status testing.
- HER2/neu receptor status testing.
- Gene profile testing by microarray assay or reverse transcription-polymerase chain reaction (e.g., MammaPrint, Onco type DX).
Although certain rare inherited mutations, such as those of BRCA1 and BRCA2, predispose women to develop breast cancer, prognostic data on BRCA1 /BRCA2 mutation carriers who have developed breast cancer are conflicting; these women are at greater risk of developing contralateral breast cancer. Since criteria for menopausal status vary widely, some studies have substituted age older than 50 years as a surrogate for the postmenopausal state. Breast cancer is classified into a variety of histologic types, some of which have prognostic importance. For example, favorable histologic types include mucinous, medullary, and tubular carcinoma.[19,20,21]
Pathologically, breast cancer can be a multicentric and bilateral disease. Bilateral disease is somewhat more common in patients with infiltrating lobular carcinoma. Patients who have breast cancer should have bilateral mammography at the time of diagnosis to rule out synchronous disease. The role of magnetic resonance imaging (MRI) in screening and follow-up continues to evolve. Having demonstrated an increased detection rate of mammographically occult disease, the selective use of MRI for additional screening is being used with increased frequency despite the absence of randomized, controlled data. Because only 25% of MRI-positive findings represent malignancy, pathologic confirmation prior to treatment action is recommended. Whether this increased detection rate will translate into improved treatment outcome is unknown.[22,23,24] When BRCA1 /BRCA2 mutation carriers were diagnosed at a young age, the risk of a contralateral breast cancer reached nearly 50% in the ensuing 25 years.[25,26]
Patients should continue to have regular breast physical examinations and mammography to detect either recurrence in the ipsilateral breast in those patients treated with breast-conserving surgery or a second primary cancer in the contralateral breast. The risk of a primary breast cancer in the contralateral breast is approximately 1% per year.[28,29] Patient age younger than 55 years at the time of diagnosis or lobular tumor histology appear to increase this risk to 1.5%. The development of a contralateral breast cancer is associated with an increased risk of distant recurrence.[31,32]
Hormone Replacement Therapy
The use of hormone replacement therapy (HRT) poses a dilemma for the rising numbers of breast cancer survivors, many of whom enter menopause prematurely as a result of therapy. HRT has generally not been used for women with a history of breast cancer because estrogen is a growth factor for most breast cancer cells in the laboratory; however, empiric data on the safety of HRT after breast cancer are limited.[33,34]