ISSN 2398-2985      

Neoplasia overview

6guinea pig

Synonym(s): Tumors, Cancer


  • Cause: neoplasias of many kinds have been documented in guinea pigs. The most common tumors of guinea pigs are pulmonary adenoma (bronchogenic papillary adenoma), followed by cutaneous tumors.
  • Signs: cutaneous neoplasias present with masses or lumps. Lethargy, anorexia, weight loss, poor hair coat, signs of pain, dyspnea.
  • Diagnosis: complete blood counts, serum chemistries, urinalysis. Radiography, ultrasonography, CT, MRI. Fine needle aspiration of masses with cytology. Surgery: excision, biopsy with histopathology.
  • Treatment: for leukemia/lymphoma chemotherapy is used. For most cutaneous masses surgical excision. For reproductive tract tumors surgical removal of reproductive organs.
  • Prognosis: if the mass can be fully excised, prognosis may be good. Mammary gland adenocarcinomas may be difficult to fully excise as they invade surrounding tissues.
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  • Although it is considered that true neoplastic processes are rare in guinea pigs as compared to other mammals, pet guinea pigs that are living longer than those used in research or for food present more frequently to practitioners with tumors. Many types have been described.
  • The most common tumors of guinea pigs are pulmonary adenoma Pulmonary neoplasia (bronchogenic papillary adenoma), followed by cutaneous tumors.
  • Pulmonary adenoma (bronchogenic papillary adenoma Pulmonary neoplasia. Pulmonary adenomas are estimated to affect at least 35% of guinea pigs over 3 years of age. Usually they are not associated with clinical signs until they become large severe and impede respiration. Many are found incidentally at necropsy.
  • Mammary gland adenocarcinoma Mammary gland adenocarcinoma.
  • Cavian leukemia Leukemia/lymphosarcoma Lymphosarcoma. A type C retrovirus has been linked with cavian leukemia.
  • Cutaneous neoplasia Cutaneous neoplasia. Cutaneous tumors are estimated to affect up to 15% of aged guinea pigs:
    • Trichofolliculomas are the most common cutaneous tumor.
    • These develop from hair follicles where there are abortive follicular adnexal structures in the walls of cysts.
    • Lipomas are benign and the second most common cutaneous tumor.
    • Trichoepitheliomas Trichoepithelioma.
    • Sebaceous adenoma Sebaceous adenoma.
    • Soft tissue sarcoma.
    • Fibrosarcoma.
    • Fibrolipoma.
    • Fibropapilloma (ear canal).
    • Mammary gland adenoma/cystadenoma, fibroadenoma.
    • Carcinoma (exact cutaneous cell line not determined).
    • Squamous cell carcinoma.
    • Malignant melanoma.
    • Liposarcoma .
    • Cutaneous hemangiosarcoma.
    • Epitheliotropic lymphoma.
  • Reproductive tract tumors:
    • Ovarian teratoma : teratomas that can contain tissues of organ types form the three germ layers, including nervous, endocrine, skin and muscle tissue. It is usually unilateral, benign and unlikely to metastasize. This may resemble non-neoplastic embryonal structures within the ovary and like placentomas may be transitory and replaced by fibrosis. These may grow large, up to 10 cm in diameter.
    • Ovarian adenocarcinoma.
    • Granulosa cell tumors may be associated with cystic rete ovarii.
    • Uterine leiomyoma, leiomyosarcoma. Uterine leiomyoma is the most common, and is usually associated with cystic rete ovarii. Leiomyomas are the most common reproductive tract tumors in guinea pigs usually over 4 years of age.
    • Testicular tumors.
    • Penile papillomas.
  • Adrenocortical adenomas.
  • Mesenchymal tumors.
  • Islet cell tumors (insulinoma).
  • Thyroid tumors Hyperthyroidism:
    • Macrofollicular thyroid adenoma.
    • Thyroid cystadenoma.
    • Papillary thyroid adenoma.
    • Follicular thyroid carcinoma.
    • Follicular-compact thyroid carcinoma.
    • Small-cell thyroid carcinoma.
  • Osteosarcomas .
  • Gliomas.
  • Amelioblastomas.
  • Gastric leiomyoma, adenocarcinoma.
  • Cecal adenocarcinoma.
  • Bile duct tumors.
  • Mixed tumors (myxomas, benign) are the most commonly reported tumors of the cardiovascular system.

Predisposing factors


  • Aging.


  • Spontaneous neoplasia is relatively uncommon in guinea pigs:
    • Usually occurs over 3 years of age, but has been seen as early as 4 months of age.
    • There are some anatomy/physiology features that are thought to decrease neoplasias.
    • A serum factor thought to be asparaginase has anti-tumor activity.
    • Kurloff cells functioning as NK cells have anti-tumor activity.  
  • Uterine Uterine neoplasia and ovarian tumors Cystic ovarian disease can be induced by exposure to estradiol, diethylstilbestrol or testosterone.
  • Cutaneous tumors Cutaneous neoplasia may ulcerate and become secondarily infected which results in exudation. There may be alopecia over the tumor.


  • Many are slow growing.
  • A tumor that ulcerates may become infected within a few days.


  • Leukemia Leukemia due to a type-c retrovirus is contagious, although neonates and stressed guinea pigs are most at risk.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Gardhouse S M, Guzman D S-M, Sadar M J et al (2016) Partial gastrectomy for resection of a gastric leiomyoma in a guinea pig (Cavia porcellus). JAVMA 249 (12), 1415-1420 PubMed.
  • Gibbons P M, Garner M M & Kiupel M (2012) Morphological and immunohistochemical characterization of spontaneous thyroid gland neoplasms in guinea pigs (Cavia porcellus). Vet Pathol 50 (2), 334-342 PubMed.
  • Schuetzenhofer G, Goericke-Pesch S & Wehrend A (2011) Effects of deslorelin implants on ovarian cysts in guinea pigs. Schweiz Arch Tierheilkd 153 (9), 416-417 PubMed.
  • Greenacre C B (2004) Spontaneous tumors of small mammals. Vet Clin Exot Anim 7 (3), 627-651.
  • Silva E G, Tornos C, Deavers M et al (1998) Induction of epithelial neoplasms in the ovaries of guinea pigs by estrogenic stimulation. Gynecol Oncol 71 (2), 240-246 PubMed.
  • Silva E G, Tornos C, Fritsche H A Jr et al (1997) The induction of benign epithelial neoplasms of the ovaries of guinea pigs by testosterone stimulation: a potential animal model. Mod Pathol 10 (9), 879-883 PubMed.
  • Porter K B, Tsibris J C, Nicosia S V et al (1995) Estrogen-induced guinea pig model for uterine leiomyomas: do the ovaries protect? Biol Reprod 52 (4), 824-932 PubMed.

Other sources of information

  • Brabb T, Newsome D, Burich A et al (2012) Infectious Diseases (Guinea Pig Section III). In: The Laboratory Rabbit, Guinea Pig, Hamster and other Rodents. Eds: Suckow M A, Stevens K A & Wilson R P. Academic Press. pp 637-684.
  • Hawkins M G & Bishop C R (2012) Disease Problems of Guinea Pigs. In: Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. 3rd edn. Eds: Quesenberry K E & Carpenter J W. Elsevier. pp 295-310.
  • Harkness J E, Turner P V, Vandewoude S & Wheler C L (2010) Harkness and Wagner’s Biology and Medicine of Rabbits and Rodents. 5th edn. Wiley-Blackwell. pp 342-343.
  • Percy D H & Barthold S W (2007) Guinea Pigs. In: Pathology of Laboratory Rodents and Rabbits. 3rd edn. Eds: Percy D H & Barthold S W. Blackwell Publishing. pp 217-251.
  • Harkness J E, Murray K A, Wagner J E (2002) Biology and Diseases of Guinea Pigs. In: Laboratory Animal Medicine. 2nd edn. Eds: Fox J G, Anderson L C, Loew F M & Quimby F W. Academic Press. pp 203-246.

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