Figure 2. Histopathology of Experimental Lymphedema in the Murine Tail.

Lymphedema was characterized by the presence of marked acute inflammatory changes, both adjacent to the surgical site and within distal regions of the tail, remote from the site of surgical ablation.

(A) Normal tail skin harvested 16 mm from the base of the tail is characterized by the presence of a thin dermis and epidermis, with a normal epidermal/dermal junction. Surgical sham controls were indistinguishable from normals, with no increased cellularity in dermis or epidermis, and no enlarged nuclei or hyperkeratosis.

(B) Lymphedematous skin harvested immediately distal to the site of prior surgical lymphatic ablation is characterized by the presence of marked acute inflammatory changes, absent in the tissue derived from the normal tails. There is a notable increase in cellularity, with an increase in the number of observed fibroblasts and histiocytes, as well as a large infiltration of neutrophils. There is hyperkeratosis and spongiosis and edema of the epidermis, with irregularity of the epidermal/dermal junction, elongation of the dermal papillae, and a 2- to 3-fold expansion of tissue between the bone and the epidermis. There are numerous dilated lymphatic microvessels in the dermis and subdermis (black arrows). In contrast, normal tail sections were devoid of these dilated structures.

(C) Normal skin derived from the distal tail. No inflammation, hypercellularity, or lymphatic dilatation is observed.

(D) Distal skin in lymphedema. Spongiosis and lymphatic microvascular dilatation (black arrows) are once again detectable.