Lymph node micro-architecture can be imaged using optical coherence tomography.

Abstract

Abstract Abstract #804 Background: Histological assessment is the gold standard technique for identification of lymph node involvement in breast cancer. However, this may only be performed ex vivo and will often result in the unnecessary excision of healthy lymph nodes. In axillary clearance, this will result in lymphedema in approximately 26% of patients. Optical Coherence Tomography (OCT) is a real-time imaging modality with the potential to perform in vivo optical biopsy of lymph nodes. We undertook ex vivo imaging of excised lymph nodes to identify which aspects of the lymph node micro-architecture could be imaged using OCT, and to identify differences between cancerous and normal nodes.
 Materials and Methods: 18 lymph nodes were taken from 13 patients undergoing axillary clearance or sentinel lymph node biopsy. Fresh excised lymph tissue was dissected into 2mm slices. A 3D-OCT scan was acquired, with a resolution of ∼11μm in both axial and lateral dimensions. Each sample underwent subsequent histological analysis using Haematoxylin and Eosin (H&E) staining and matched against the 3D-OCT data sets.
 Results: OCT images demonstrated differentiation of the three major tissue types found in the lymph node: adipose, lymph cortex and lymph capsule. Adipocytes demonstrated a characteristic honeycomb structure that was also visible in H&E stained histology. The cortex, containing a high concentration of lymphocytes, was found to give a strong level of optical backscatter in the OCT image. The capsule, consisting of less dense stroma tissue, could generally be differentiated from the cortex. Small blood vessels in the stroma and cortex presented as areas of low backscatter. Sinuses were identified as contributing to variation in intensity within the cortex. Germinal centers could be distinguished from resting lymphoid tissue by a characteristic circular structure apparent in both OCT and histology. Cancerous regions were found to be devoid of these characteristic micro-architectural structures, as the malignant cells replaced normal lymph tissue. Figure 1 shows the H&E histology image and corresponding OCT scan of a normal lymph node. Adipose, cortex, stroma and small blood vessels are all apparent in this sample.
 Discussion: These results demonstrate that OCT is able to differentiate relevant structures within lymph nodes. Our findings suggest that lymph node metastasis is evident by the lack of these structures. This corresponds well with histological findings. This work forms a basis for future in vivo studies aimed at assessing lymph node involvement prior to excision.
 
 Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 804.