Lymphangiosarcoma was diagnosed from biopsy material obtained from an
8-week-old puppy with a progressively enlarging subcutaneous inguinal
swelling. Histologically, the tumor was composed of endothelial cells
immediately adjacent to large collagen bundles. Tumor cells formed irr
egular vascular channels which extended along the connective tissue in
vestments of small vessels and nerves of the subcutis and deep dermis.
Similar neoplastic tissue extensively infiltrated an inguinal lymph n
ode. Neoplastic cells were immunohistochemically stained for factor 8-
related antigen and were weakly positive when compared with several he
mangiomas and hemangiosarcomas. Transmission electron microscopy revea
led numerous micropinocytotic vesicles and a continuous basal lamina.
The puppy was euthanatized at 8 months of age due to severe septic pol
yarthritis. Lymphangiosarcoma was documented at the site of the origin
al tumor as well as in the axillary lymph node at necropsy.