Felis ISSN 2398-2950

Thymus: neoplasia

Contributor(s): Laura Garrett


  • Old cat - tumor is most likely to be thymoma Thymoma (rare); paraneoplastic syndromes Feline cutaneous paraneoplastic syndromes may be present.
  • Young cat - most likely to be anterior mediastinal (thymic) lymphosarcoma Mediastinal lymphoma, although thymoma may occur.
  • Other thymic masses: thymic hyperplasia, thymic branchial cyst formation, thymic hemorrhage, thymic amyloidosis, other very rare neoplasms.
  • Signs: tachypnea, dyspnea due to pleural effusion Pleural effusion and mediastinal mass, paraneoplastic syndromes (rare).
  • Diagnosis: radiography, ultrasonography, cytology, histopathology.
  • Treatment: surgery, may be combined with radiotherapy Radiotherapy.
  • Prognosis: good, particularly if tumor is encapsulated; metastases very rare.




  • Mass in anterior mediastinum  →  pleural effusion, respiratory compromise.
  • It is thought that immunological abnormalities induced by the diseased thymus lead to the development of paraneoplastic syndromes.


  • Weeks although may present acutely.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kaser-Hotz B, Rohrer C R, Fidel J L et al (2001) Radiotherapy in three suspect cases of feline thymoma. J Am Anim Hosp Assoc 37 (5), 483-488 PubMed.
  • Smith A N, Wright J C, Brawner W R Jr. et al (2001) Radiation therapy in the treatment of canine and feline thymomas: a retrospective study (1985-1999). J Am Anim Hosp Assoc 37 (5), 489-496 PubMed.
  • Reichle J K, Wisner E R (2000) Non-cardiac thoracic ultrasound in 75 feline and canine patients. Vet Radiol 41 (2), 154-162 PubMed
  • Shelton G D, Ho M, Kass P H (2000) Risk factors for acquired myasthenia gravis in cats: 105 cases (1986-1998). J Am Vet Med Assoc 216 (1), 55-57 PubMed.
  • Swainson S W, Nelson O L, Niyo Y et al (2000) Radiographic diagnosis: mediastinal parathyroid cyst in a cat. Vet Radiol Ultrasound 41 (1), 41-43 PubMed.
  • Day M J (1997) Review of thymic pathology in 30 cats and 36 dogs. J Sm Anim Pract 38 (9), 393-403 PubMed.
  • Forster-van-Hijfte M A, Curtis C F & White R N (1997) Resolution of exfoliative dermatitis and Malassezia pachydermatis overgrowth in a cat after thymoma resection. JSAP 38 (10),  451-454 PubMed.
  • Galloway P E, Barr F J, Holt P E et al (1997) Cystic thymoma in a cat with cholesterol-rich fluid and an unusual ultrasonographic appearance. JSAP 38 (5), 220-224 PubMed.
  • Malik R, Gabor L, Hunt G B et al (1997) Benign cranial mediastinal lesions in three cats. Aust Vet J 75 (3), 183-187 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.
  • Anilkimar T V, Voigt R P, Quigley P J et al (1994) Squamous cell carcinoma of the feline thymus with widespread apoptosis. Res Vet Sci 56 (2), 208-215 PubMed.
  • Ellison G W, Garner M M, Ackerman N (1994) Idiopathic mediastinal cyst in a cat. Vet Radiol 35 (5), 347-349 VetMedResource.
  • Gores B R, Berg J, Carpenter J L et al (1994) Surgical treatment of thymoma in cats: 12 cases (1987-1992). J Am Vet Assoc 204 (11), 1782-1785 PubMed.
  • Scott-Moncrieff J C, Cook J R Jr., Lantz G C (1990) Acquired myasthenia gravis in a cat with thymoma. J Am Vet Med Assoc 196 (8), 1291-1293 PubMed.

Other sources of information

  • Ogilvie G K and Moore A S (1995) Thymoma in cats. In: Managing the veterinary cancer patient: a practice manual. Veterinary Learning Systems, Trenton N J,  pp 448-450.