Equis ISSN 2398-2977

Testis: neoplasia - seminoma

Contributor(s): Terry Blanchard, Graham Munroe, Elaine Watson, Anna Hollis

Introduction

  • Seminomas are the most commonly reported equine testicular tumors (0.5% intact male horses). May affect cryptorchid or descended testicles.
  • Cause: arise from cells of the spermatogenic series.
  • Signs: enlarged testicle, pendulous scrotum.
  • Diagnosis: ultrasonography, biopsy, histopathology.
  • Treatment: surgical removal by castration.
  • Prognosis: good if no metastasis.

Pathogenesis

Etiology

  • The origin of tumors is poorly understood but seminomas are thought to arise from cells of the spermatogenic series lining the seminiferous tubules.
  • Malignant tumors can be produced by certain chronic irritants.
  • It is likely that the higher ambient temperature to which inguinal and abdominal testicles are exposed is a factor in the development of tumors in these structures.
  • In the case of spontaneous tumors, a predisposition to neoplastic disease may be heritable, but this is unproven.

Pathophysiology

  • All seminomas should be considered potentially malignant: although benign forms are more common.
  • Arises from the germinal epithelium of the seminiferous tubules.
  • Locally invasive.
  • Spreading by intratubular and extratubular pathways.
  • Tunica albuginea generally restricts the tumor's expansion, but occasionally the tumor breaches the testicular capsule and spreads to adjacent tissue.
  • Metastasis of seminomas to the thoracic and abdominal cavities are possible, often to regional lymph nodes.
  • Hormonal changes in horses caused by seminomas have not been reported.

Timecourse

  • Progressive testicular enlargement occurs - sheets of neoplastic cells gradually replace normal testicular tissue.

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.
  • Weiermayer P & Richter B (2009) Simultaneous presence of a seminoma and a leiomyoma in the testes of a horse. Equine Vet Educ 21 (4), 172-176 VetMedResource.
  • Valentine B A (2009) Equine testicular tumours. Equine Vet Educ 21 (4), 177-178 VetMedResource.
  • Henson F M D & Dobson J M (2004) Use of radiation therapy in the treatment of equine neoplasia. Equine Vet Educ 16 (6), 315-318 VetMedResource.
  • Fukuda T, Kikuchi M, Kurotaki T et al (2001) Age-related changes in the testes of horses. Equine Vet J 33 (1), 20-25 PubMed.
  • Veeramachaneni D N & Sawyer H R (1998) Carcinoma in situ and seminoma in equine testis. APMIS 106 (1), 183-185 PubMed.
  • Trigo F J, Miller R A & Torbeck R L (1984) Metastatic equine seminoma - report of two cases. Vet Pathol 21 (2), 259-260 PubMed.


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