Equis ISSN 2398-2977

Teratoma

Contributor(s): Terry Blanchard, Cody Coyne, Prof Derek Knottenbelt, Graham Munroe, Katrin Schmallenbach, Elaine Watson

Introduction

  • Testicular neoplasms of the horse occur infrequently, probably because most horses are castrated at an early age.
  • Much higher incidence in retained testicles.
  • Cause: comprised of cells derived from all three germ layers (endoderm, mesoderm, ectoderm)   →   mixed tumor.
  • Signs: unilateral testicular enlargement, pendulous scrotum.
  • Diagnosis: inguinal palpation, rectal palpation, ultrasonography. Confirmed by gross examination of testis.
  • Treatment: surgical removal.
  • Prognosis: good.

Pathogenesis

Etiology

  • The origin of tumors is unknown.
  • It is postulated that the higher ambient temperature to which inguinal and abdominal testicles are exposed is a factor in the development of teratomas in these structures.
  • It has been postulated that teratomatous testicles may be congenital.

Predisposing factors

General
  • In contrast to humans and dogs, for horses, a relationship between cryptorchidism   Testis: cryptorchidism  and formation of testicular neoplasia has not been established.
  • It is thought that teratoma development might prevent testicular descent, rather than cryptorchidism predisposing the animal to the development of teratomas.

Pathophysiology

  • Most frequently located in the gonads in horses.
  • Benign.
  • Classified as germinal tumor, as they derive from pluripotential germ cells.
  • Complex tumor, composed of a disorderly arrangement of recognizable tissues not native to the testis (bone, cartilage, skin).
  • Only contain mature elements.
  • Neoplastic tissue may be present in late fetal life, impeding normal testicular descent into the scrotum.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Arensburg L, Olivier S, Boussawu B & De Cock H (2012)An abdominal teratoma in a yearling Irish Cob with a strangulating obstruction of the small intestine.Equine Vet Educ24(9), 433-436 VetMedResource.
  • Valentine B A (2009)Equine testicular tumours.Equine Vet Educ21(4), 177-178 VetMedResource.
  • Pollock P J, Prendergast M, Callanan J J & Skelly C (2002)Testicular teratoma in a three-year-old thoroughbred foal.Vet Rec150(11), 348-350 PubMed.
  • May K A, Moll D, Duncan R S, Pleasant R S & Purswell B J (1999)Unilateral Leydig cell tumour resulting in acute colic and scrotal swelling in a stallion with descended testes.Equine Vet J31(4), 343-345 PubMed.
  • Schumacher J (1999)Testicular neoplasia of horses - an underreported condition.Equine Vet J31(4), 270-272 PubMed.
  • Arighi Met al(1987)Histology of the normal and retained equine testis.Acta Anat (Basal)129(2), 127-130 PubMed.
  • Stick J A (1980)Teratoma and cyst formation of the equine cryptorchid testicle.JAVMA176(3), 211-214 PubMed.
  • Smyth G B (1979)Testicular teratoma in an equine cryptorchid.Equine Vet J11(1), 21-23 PubMed.


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