Excision of cutaneous tumors in the horse using histologic guidance.

A highly successful surgical technique for removing cutaneous tumors in humans was used in seven horses with cutaneous squamous cell carcinoma (n = 3) or sarcoid (n = 4). In humans, the complete underside of the tumor is evaluated histologically by processing horizontal sections from the tumor base, and orientation between the wound surface and the undersurface of the excised tumor is maintained by mapping both surfaces. The technique ensures that small foci of residual tumor can be located accurately and removed. Based on our experience, three modifications of the human technique are suggested for its use in horses. The equine patient should be placed under general anesthesia rather than using local anesthesia if the tumor is in a difficult position for standing surgery or the patient is uncooperative; useful information can be obtained from tissue processed in buffered formalin if frozen sections are not available; and optimal tumor size for this procedure is no larger than 3 x 2 cm.