Angiokeratoma with lysosomal dilatation in keratinocytes in a dog: a case report

Herein, we report the histopathology of angiokeratoma characterised by non-invasive, proliferative, ectatic vascular malformations accompanying lysosomal dilation in the canine skin. Two cutaneous angiokeratomas were diagnosed in a six-year-old spayed female Pekinese dog. Physical examination of the skin revealed two small erythematous papules on the axillary and abdominal regions. The masses were approximately 2-3 mm in diameter, well-circumscribed, purple to red in colour, and slightly elevated above the skin surface. The two small masses had similar histopathological features, characterised by exophytic proliferation of a mixture of multiple vascular channels resembling a cavernous haemangioma on the superficial dermis. The entire lesion was well circumscribed and the overlying epidermal hyperplasia formed a collarette. Ultrastructural analysis with transmission electron microscopy revealed electron-lucent lysosomal dilatation in the keratinocytes of the irregular hyperplastic epithelial trabeculae like rete pegs.