Surgical Treatment of External Genital Tumors in Horses

Horses with extensive or invasive tumors of the external genitalia may require surgical intervention for successful treatment. Solitary tumors may be removed completely by local excision, laser ablation, cryotherapy, or circumferential posthectomy (i.e., reefing). Horses with advanced lesions involving the glans or body of the penis warrant phallectomy, whereas horses with infiltrative lesions of the penis and prepuce with suspected or confirmed metastasis to lymph nodes require en bloc resection and penile retroversion. This article describes the indications, procedures, aftercare, and potential complications for each surgical technique. Anticancer drugs administered perioperatively may improve outcome in select cases, and indications for their use are discussed as well. Although many horses with external urogenital tumors can be treated successfully with radiotherapy, immunotherapy, or chemotherapy, surgical intervention may be required to achieve a successful outcome in horses with advanced tumors. Current methods of radiotherapy and intratumoral or topical chemotherapy are restricted to the treatment of horses with superficial tumors. Extension of a tumor into deep structures, such as the penile tunics, warrants aggressive surgical intervention for local control. Primary factors that influence the choice of surgical procedure include tumor location, histologic type, and extent of tumor growth. Surgical procedures include local tumor excision, laser ablation, cryosurgery, circumferential posthectomy, phallectomy, and en bloc penile resection and retroversion. Although the importance of eliminating the tumors should outweigh cosmesis, some clients may consider cosmetic outcome important in the selection of treatment. The decision to perform radical procedures, such as phallectomy or en bloc resection of the distal penis, is more easily made in male horses not used for breeding. Horses whose breed registry requires natural cover (e.g., ThoroughCE 570 Vol. 24, No. 7 July 2002 n Local excision is usually successful treatment of horses with solitary, focal tumors of the external genitalia that have not invaded deeper tissues. n Cryotherapy or carbon dioxide lasers can be used to excise tumors or ablate precancerous