Lymphatic anatomy

Introduction: The introduction of lymphoscintigraphy and sentinel node biopsy (SNB) has revealed previously unrecorded and unexpected pathways of lymphatic drainage of the integument. This has demanded a reappraisal of the anatomy of the lymphatic network since current knowledge is based on the works of Sappey performed in the 1870s before radiology and microphotography. Our studies have focused on this problem: 1. To re-evaluate the lymphatic anatomy of the integument and thereby: 2. Validate or refute the technique of sentinel node biopsy. 3. Define previously unrecorded lymphatic pathways detected by SNB. 4. Compare the lymphatic and venous anatomy. 5. Help explain some unusual clinical findings of melanoma metastasis. 6. Provide new methods to treat lymphoedema. Methods: 1. Human cadaver lymphatic vessel detection with hydrogen peroxide, injection with a radiopaquelead oxide mixture, antegrade dissection of lymphatic pathways – recorded by photography and radiology; retrograde tracing from sentinel nodes to define lymphatic territories and venous injections with radiolucent dye or air for comparison. 2. Similar animal cadaver studies. 3. Immunohistochemistry of the lymphatic network in the mouse. Results: 1. Avalvular lymphatic capillaries connect the valved pre collecting and collecting lymphatics of adjacent lymphatic territories. 2. Collecting lymphatics have uniform diameter whereas veins enlarge as they drain proximally. 3. Collectors concentrate near major subcutaneous veins. 4. Sentinel node territories well defined in upper limb and chest, supporting SNB in these regions. Branching of collectors within territories is common but is rare between territories. 5. Head and neck territories variable with some regions draining to multiple sentinel nodes. 6. Breast drainage sometimes to single node other times to multiple sentinel nodes. The same pattern is found between the sexes. 7. Large axillary node often drained both upper limb and chest. 8. Retrograde pathways, via dermal capillaries, detected between obstructed and patent collectors in cadaver with previous axillary dissection – helps explain dermal seeding in melanoma metastases. 9. Occasional lymphatic-venous connections detected. 10. Collecting lymphatics detected accompanying perforating blood vessels to reach deep sentinel nodes that bypass the axilla and the groin. Conclusion: Our preliminary studies support validity of SNB technique in upper limb and chest.