High BMI adversely influences successful mapping of SLNs. Patient age did not alter SLN localisation in the ALMANAC trial (11), though it has been reported in several other studies which have shown that accurate identification of the SLN decreases with increasing age as well as weight (31, 68, 69). The specific causes for mapping failure in overweight patients are unclear. Sentinel node identification may be difficult in obese women because of the higher content of subcutaneous and axillary adipose tissue. Furthermore, the increased fatty tissue may impede the flow of the tracer through the lymphatics in the breasts of these patients. Additionally, the lymph nodes in obese patients may have undergone fatty degeneration reducing their capacity to concentrate the tracer.
Older women (>50 years) are more likely to have failure of SLN visualisation on preoperative lymphoscintigraphy (23). There is a decrease in tissue turgor in older women, with a resultant decrease in the hydrostatic intralymphatic pressure that drives the mapping agent into the node. Even if the agent is delivered successfully to the node, it may not be concentrated because of the limited sinusoidal space that remains in a fat-replaced node, another feature found more commonly in older patients.
These findings, however, do not contraindicate SLNB in these individuals as the rate of successful localisation remains high and unsuccessful mapping does not adversely affect their prognosis or treatment.
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