Identification of the internal mammary lymph node metastasis by FDG-PET/CT in breast cancer

Objectives The presence of internal mammary (IM) lymph node metastases in breast cancer predicts outcome and may alter treatment. We performed a retrospective review of women who underwent FDG-PET/CT prior to treatment to determine the benefit of PET for imaging IM metastasis.

Methods The records of 9 consecutive patients with abnormal IM uptake on FDG-PET/CT were reviewed. IM uptake on-FDG PET/CT was compared with the result of IM biopsy.

Results The pathologic stage was IIIc in all patients. IM metastasis was confirmed in all patients by histopathological studies. PET identified lymph node metastasis in all patients. The number of biopsy proven IM metastasis was 25 and the number of IM uptake was 13. One patient has 11 IM metastatic nodes but lymph nodes with FDG uptake was 2. One IM node with FDG uptake was no metastasis. The overall sensitivity and specificity, positive predictive value, and negative predictive value of PET/CT in the diagnosis of IM lymph node metastasis were 20%, 88%, 92%, and 35%. The SUV max and the size of IM lymph node with FDG uptake on PET/CT was 3.8±2.1 and 5.6± 2.0mm. IM uptake on PET was not associated with size of the lymph node (P>0.05).

Conclusions FDG PET/CT may identify nodal metastasis not identified by other diagnostic methods. The high PPV suggested that IM uptake on PET meaned IM metastasis of breast cancer even though IM lymph node was small or low FDG uptake