الفهرس 
ANATOMY OF BREASTOnly 14 pages are availabe for public view
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Abstract
B
reast cancer is the most commonly diagnosed cancer and the leading cause of cancer death in women. The incidence is increasing and a woman now has a 1 in 8 chance of developing breast cancer in her lifetime.
Mortality for patients with breast cancer decreased significantly, largely because of early detection or screening for breast cancer and advances in medical care and treatments.
Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) is a functional imaging technique that has demonstrated advantages over anatomically based imaging modalities in oncology in the detection of malignant lesions.
The main drawback of PET in tumor imaging is the virtually complete absence of anatomic landmarks, which impedes precise localization of lesions. Furthermore, there are some issues regarding specificity because FDG is not only taken up by many malignant tumors but also by sites of active inflammation.
The recent introduction of PET /CT systems allows the co-registration of functional PET and anatomical CT images. A novel combined PET/CT system has been built that improves the capacity to correctly localize and interpret FDG uptake.
The principal applications of [18F]FDG-PET are in disease re-staging and treatment monitoring . However, other possible indications are preoperative staging and primary diagnosis.
The ability of PET to detect breast cancer greatly depends on tumor size. Sensitivity for tumors less than 1 cm was only 25%.
The restricted sensitivity of FDG-PET does not allow the screening of asymptomatic women for breast cancer.
The major limitation of PET or PET/CT for breast imaging is its poor detection rate for small breast carcinomas and non-invasive breast cancers However, PET/CT has a role to play in a selected group of patients, such as those with dense breasts or with implants, for determining tumor multiplicity, for localizing the primary tumor in those patients with metastases of a breast origin when the mammography is indeterminate, and for those patients whom biopsy is not a desirable option.
Advances in technology such as the development of dedicated breast imaging devices (eg, positron emission mammography) may improve the detection of primary tumors with PET in the future.
High uptake of 18F-FDG would be predictive of poor prognosis in patients with primary breast cancer, and aggressive features of cancer cells in patients with early breast cancer. 18F-FDG PET/CT could be a useful tool to pre-therapeutically predict biological characteristics and baseline risk of breast cancer.
Among patients who have larger tumors, sentinel biopsy can be avoided in those who have positive FDG-PET, in whom complete axillary lymph node dissection should be the primary procedure.
Small axillary metastases are frequently missed at FDG PET and it cannot demonstrate the number of lymph nodes involved. In addition, FDG uptake in lymph nodes is not specific for malignancy; a generalized inflammatory response of regional lymph nodes to infection or recent biopsy or surgery is also a common source of increased FDG uptake.
In patients who have locally advanced disease and who are undergoing primary chemotherapy, however, FDG-PET seems to be a reliable method to determine the extent of disease.
Despite the limitation in detection of small tumor deposits, FDG-PET is currently the most sensitive imaging modality to detect lymph node metastases, including parasternal and mediastinal nodes .
The metastasis to the internal mammary or mediastinal lymph nodes in breast cancer patients is often clinically occult. PET/CT is more useful than CT for evaluating the internal mammary and mediastinal lymph nodes .
One advantage of whole-body PET imaging over conventional imaging modalities is its ability to detect metastasis at different sites and organs during a single examination.
Several studies have shown that FDG PET is superior to bone scintigraphy in detecting osteolytic and intramedullary metastases. However, FDG PET frequently fails to demonstrate osteoblastic lesions, which are readily detected with bone scintigraphy .
Yet PET/CT can overcome this limitation, and osteoblastic bone lesions, even if negative on PET scans, can be identified on CT images.
In clinical practice, the combination of bone scintigraphy and CT remains the standard imaging combination for staging breast cancer, and FDG PET is most helpful in clarifying difficult or equivocal cases.
The tumour uptake of [18F] FDG after one or two cycles of chemotherapy is predictive of therapy response, as evaluated by CT at the end of treatment. PET imaging is highly useful for monitoring therapeutic effects at an earlier stage than is possible with other currently available imaging procedures.
While bone scanning, MR imaging, and CT are effective in detecting bone metastases, it can be difficult to discern changes in response to therapy with these modalities.
Serial FDG PET can be helpful in measuring bone metastasis response and that changes in FDG uptake correlate with clinical response and changes in breast cancer tumor markers.
PET is considered to be highly effective for evaluating patients with suspected recurrent breast cancer, and it surpasses the other conventional imaging modalities in terms of whole-body evaluation. The CT data from a PET/CT examination allows the appropriate anatomical localization of foci of FDG uptake.
FDG PET is particularly useful for discrimin-ating between viable tumor and post-therapy changes such as necrosis or fibrotic scarring in patients with equivocal results of anatomic imaging.
FDG PET and FDG PET/CT may be useful for evaluating asymptomatic treated breast cancer patients with rising levels of tumor markers without clinical symptoms.
The current data suggest that 18F-FES- PET is sensitive to detect ER-positive tumor sites, and complements the information provided by 18F-FDG to assess or predict response to therapy and also might be useful to predict the response to second-line hormonal therapy in recurrent or metastatic breast cancer.
In conclusion:
The principal applications of PET/CT in breast cancer are in disease re-staging and treatment monitoring and in clarifying difficult or equivocal cases.