Background: The view that breast cancer-related lymphedema (BCRL) is a simple, direct mechanical result of axillary lymphatic obstruction (‘stopcock’ mechanism) appears incomplete, because parts of the swollen limb (e.g., hand) can remain nonswollen. The lymph drainage rate constant (k) falls in the swollen forearm but not in the spared hand, indicating regional differences in lymphatic function. Here the generality of the hypothesis that regional epifascial lymphatic failure underlies regional swelling was tested. To do so, the regional distribution of epifascial swelling along the forearm was compared with that of epifascial (subcutis) k.

Methods and Results: Epifascial k (local lymph flow per unit distribution volume) was measured by quantitative lymphoscintigraphy of subcutaneous radiolabeled human immunoglobulin IgG in regions of maximal and minimal % swelling in the ipsilateral swollen forearm, and at matching sites in the contralateral nonswollen arm, in 11 women with BCRL. Swelling was maximal distally in 5 patients and proximally in 6. Proximal k, −0.085 ± 0.025% min⁻¹ (mean ± SD), was 27% bigger than distal k, −0.067 ± 0.021% min⁻¹, irrespective of swelling (p = 0.02, two-way repeated measures ANOVA). k fell by 11% from −0.080 ± 0.028% min⁻¹ in the nonswollen arm to −0.072 ± 0.021% min⁻¹ in the swollen arm (p = 0.17, t test). Local epifascial k was not significantly lower, however, at sites of maximal swelling than minimal swelling, and k correlated positively with arm circumference.

Conclusions: A systematic difference in lymph drainage along the axis of the forearm was demonstrated for the first time. Local differences in epifascial k did not, however, explain the regionality of swelling, in keeping with previous evidence that epifascial k does not correlate with differences in swelling between arms, whereas subfascial k does. The results lead to the rejection of the hypothesis that epifascial (cf. subfascial) lymph drainage rate constants govern epifascial swelling in human forearm.