Cutaneous metastatic tumors (ie, thespread of a primary neoplasm to the skin) are unusual in domestic animals, being occasionally identified in dogs, less common in cats, and rare in horses, cows, sheep, goats, and pigs. Although all malignant neoplasms are capable of secondary cutaneous involvement, metastatic potential is greatest in mammary gland adenocarcinomas, squamous cell carcinomas, transitional cell carcinomas, transmissible venereal tumors, pulmonary adenocarcinomas, and angiosarcomas.
Although appearance is variable, the lesions most commonly are multiple, ulcerated papulonodules. Early cutaneous metastasis is characterized by aggregates of neoplastic cells within superficial and deep dermal vessels. As these lesions evolve, they extend into the dermis and are associated with effacement of adnexa. Generally, it is difficult to distinguish the primary neoplasm based on the morphologic features of a metastatic site. This is because only a small population of cells in the primary tumor have the potential for metastasis, and these cells may have different microscopic features.
In cats, pulmonary adenocarcinomas appear to preferentially metastasize to the distal extremities (lung-digit syndrome), and when carcinomas are diagnosed on multiple feet, radiographic examination for a primary lung tumor should be performed.
Cutaneous metastasis is usually a feature of aggressive tumors and is associated with a guarded to poor prognosis.
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Also see pet health content regarding tumors of the skin in dogs Tumors of the Skin in Dogs Tumors are abnormal growths of cells. Tumors affecting the skin or the tissue just under the skin are the most commonly seen tumors in dogs. Skin tumors are diagnosed more frequently than other... read more , cats Tumors of the Skin in Cats Tumors are abnormal growths of cells. Tumors affecting the skin or the tissue just under the skin are the most commonly seen tumors in cats. This is partly because they are the most easily seen... read more , and horses Tumors of the Skin in Horses Tumors are abnormal new growths of cells, also called neoplasms. Neoplasms affecting the skin or the tissue just under the skin are the most commonly seen tumors in horses. Skin tumors are diagnosed... read more .