title: Penile and preputial tumours in the horse: a retrospective study of 114 affected horses.
abstract: BACKGROUND
  Preputial and penile tumours are more common in horses than in other domestic animals, but no large surveys of male horses with tumours of the external genitalia are available.
  
  
  OBJECTIVE
  To present a retrospective analysis of male horses with neoplasms of the external genitalia.
  
  
  METHODS
  The penile and preputial tumours of 114 horses were evaluated. Data recorded included age, gelding or stallion and breed; type and site of lesion; involvement of regional lymph nodes; histopathology (including grading of squamous cell carcinoma); and results of radiographic examination of the thorax.
  
  
  RESULTS
  Mean age of horses was 19.5 years with no apparent breed predilection. Common presenting clinical signs were irregularities (e.g. the presence of a mass and/or ulceration) on the integument of the penis and prepuce, and purulent or sanguineous discharge from preputial orifice. Squamous cell carcinoma (SCC) was the most prevalent neoplasm followed by papillomas and melanomas. A basal cell carcinoma, neurofibrosarcoma, adenocarcinoma or fibrosarcoma were each found on single horses. Squamous cell carcinomas with poor differentiation had a higher tendency to metastasise than did more differentiated tumours.
  
  
  CONCLUSIONS
  Squamous cell carcinoma is the most common urogenital tumour of the male horse and occurs primarily in old horses. Horses with poorly differentiated SCCs tend to have a higher incidence of regional metastases. Pathology of lymph nodes, even when not palpably enlarged, is a valuable diagnostic exercise. Radiology of the thorax to detect lung metastases is of little value.
authors.affiliation: Department of Equine Sciences, Utrecht University, Yalelaan 114, 3584 CM, Utrecht, The Netherlands.
authors.forename: J G B
authors.initials: JG
authors.lastname: van den Top
authors.forename: N
authors.initials: N
authors.lastname: de Heer
authors.forename: W R
authors.initials: WR
authors.lastname: Klein
authors.forename: J M
authors.initials: JM
authors.lastname: Ensink
mesh_terms: D000367:Age Factors; D000818:Animals; D001947:Breeding; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D006734:Horse Diseases / Q000453:epidemiology / Q000473:pathology* / Q000601:surgery; D006736:Horses; D008198:Lymph Nodes / Q000473:pathology / Q000601:surgery; D008207:Lymphatic Metastasis / Q000175:diagnosis; D008297:Male; D009362:Neoplasm Metastasis / Q000175:diagnosis; D009367:Neoplasm Staging / Q000662:veterinary; D009919:Orchiectomy / Q000662:veterinary; D010212:Papilloma / Q000453:epidemiology / Q000473:pathology / Q000601:surgery / Q000662:veterinary; D010375:Pedigree; D010412:Penile Neoplasms / Q000453:epidemiology / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D010413:Penis / Q000473:pathology / Q000601:surgery; D012189:Retrospective Studies; D014521:Urethra / Q000473:pathology / Q000601:surgery