Canis ISSN: 2398-2942

Thymoma

Contributor(s): Vetstream Ltd

Introduction

  • Thymoma is an invasive, slow-growing tumor in anterior mediastinum - distant metastases have not been described in the dog.
  • Often associated with paraneoplastic syndromes : myesthenia gravis Myasthenia gravis , megaesophagus (up to 40% of cases), polymyositis , hypercalcemia Hypercalcemia: overview. May occur with other tumors (lymphoma Lymphoma , osteosarcoma Osteosarcoma: axial skeleton , adenocarcinoma Adenoma / adenocarcinoma ).
  • Diagnosis: radiography, ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), cytology, histopathology, other procedures, eg immunological tests for serum acetylcholine-receptor antibody, electromyography, electrocardiography, may be indicated.
  • Treatment: surgery, may be combined with radiotherapy.
  • Prognosis: guarded to poor.

Pathogenesis

Etiology

  • Tumor of thymic epithelial cells.
  • May be benign or malignant.

Pathophysiology

  • Mass in anterior mediastinum → compression of airway.
  • It is thought that immunological abnormalities induced by the diseased thymus lead to the development of paraneoplastic syndromes.
  • Epithelial cells promote T-cell proliferation and differentiation in benign form.
  • Malignant neoplasia is locally invasive → hemorrhage into mediastinum.

Timecourse

  • Weeks to months.

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.
  • Smith A N et al (2001) Radiation therapy in the treatment of canine and feline thymonas: a retrospective study (1985-1999). J Am Anim Hosp Assoc 37 (5), 489-496 PubMed.
  • Wood S L, Rosenstein D S & Bebchuk T (2001) Myasthenia gravis and thymoma in a dog. Vet Rec 148 (18), 573-574 PubMed.
  • Day M J (1997) Review of thymic pathology in 30 cats and 36 dogs. JSAP 38 (9), 393-403 PubMed.
  • Meleo K A (1997) The role of radiotherapy in the treatment of lymphoma and thymoma. Vet Clin North Am Small Anim Pract 27 (1), 115-129 PubMed.
  • Atwater S W, Powers B E, Park R D, Straw R C Ogilvie G K & Withrow S J (1994) Thymoma in dogs: 23 cases (1989-1991). JAVMA 205 (7), 1007-1013 PubMed.
  • Klebanow E R (1992) Thymoma and acquired myasthenia gravis in the dog - case report and review of 13 additional cases. JAAHA 28 (1), 63-69 VetMedResource.

Other sources of information

  • Ogilvie G K & Moore A S (1995) Thymoma in dogs. In: Managing the veterinary cancer patient - a practice manual. Veterinary Learning Systems, Trenton N J pp 445-448.
  • Withrow S J & MacEwen E G (1996) Thymoma. In: Small animal clinical oncology2nd Ed Saunders W B, Philadelphia pp 530-533.


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