Background and Context:Occult primary breast cancer remains a diagnostic and therapeutic challenge in clinical practice.
Aim:To compare the diagnostic value of breast MRI and 18F-FDG PET/CT in patients with axillary lymph node metastases with no palpable mass in the breast.
Strategy/Tactics:From July 2007 to October 2013, 20 women with axillary lymph node metastases with no palpable mass in the breast were evaluated by MRI and 18F-FDG PET/CT. The MR imaging findings were reviewed, including tumor size on mass, as well as distribution pattern on non-mass lesions. Twelve of the 20 women were underwent MRI–guided second-look ultrasonography.
Programme/Policy Process: 20 lesions in 18 women (2 women had a bilateral breast carcinoma) were found and 2 women were negative with no surgery on MRI. Only five lesions were detected by 18F-FDG PET/CT. In the 18 of 20 lesions confirmed histologically, 16 lesions were primary breast carcinomas and no corresponding carcinoma was found histologically in remaining 2 breasts. On MRI, 16 lesions included 9 masses and 7 non-mass lesions with ductual and segmental enhancement. Size of masses ranged from 8 to 15 mm (mean 12 mm). Of the 5 masses detected by 18F-FDG PET/CT, size of 4 masses was all greater than 10 mm. Of the 11 carcinomas not detected by 18F-FDG PET/CT, 7 lesions showed ductual and segmental enhancement. 10 lesions were carcinomas by second-look ultrasonography-guided biopsy.
Outcomes/What was learned:Mass lesions with small size and non-mass lesions are common MRI features in patients with axillary lymph node metastases, while 18F-FDG PET/CT has limited value, especially for lesions with ductal or segmental enhancement on MRI.