Investigation of lipid composition of dissected sentinel lymph nodes of breast cancer patients by 7T proton MR spectroscopy.

ABSTRACT

PURPOSE: To determine lipid composition of excised healthy and metastatic sentinel lymph nodes of breast cancer patients, as lipids are a potential discriminatory marker for malignancy. MATERIALS AND METHODS: Ten breast cancer patients undergoing surgical nodal staging were included. (1)H-magnetic resonance spectroscopic images (MRSI) were acquired without water and lipid suppression (resolution 3.0 × 3.0 × 5.0 mm(3)). MRSI was compared to histopathology. Six groups of lipid resonances (5.4-5.2, 4.3-4.1, 2.8, 2.3-2.0, 1.6-1.3, 0.9 ppm) were identified. The intensity ratios of the total of these resonances to this total including the water resonance and of each lipid resonance to the total of all lipid resonances were determined. For statistical analysis, a mixed model was applied after logistic transformation. The results were expressed as ratios of the median values of these lipid compositions in metastatic to benign nodes. RESULTS: In all, 6/32 (19%) of the excised nodes contained metastases. The ratios of the lipid resonances 5.4-5.2, 4.3-4.1, 2.8, 2.3-2.0, 1.6-1.3, 0.9 ppm between metastatic vs. benign were 0.3, 1.2, 0.2, 0.2, 1.2, and 0.9, respectively. Only the ratios of signals from unsaturated fatty acids to the total lipid signal differed significantly. CONCLUSION: Metastatic axillary lymph nodes contained fewer unsaturated fatty acids than benign nodes. 7T (1)H-MRS may be useful for detecting axillary breast cancer metastases.