• Cause: mastocytomas, or mast cell tumors, are neoplasms arising from cutaneous mast cells. They are localized to the skin and benign, unlike in other species, where this is commonly a systemic disease.
• Signs: mastocytomas present as small, round, slightly raised skin masses.
• Diagnosis: fine needle aspiration and cytological examination, or biopsy and histopathological examination.
• Treatment: surgical excision.
• Prognosis: variable, often guarded.
• Mast cell tumors are rare in reptiles:
  • A single report of a poorly differentiated skin tumor which was locally aggressive with neoplastic lymphatic emboli and metastasis to multiple organs in an Eastern kingsnake (the snake died after the start of radiation therapy).
  • A report of multiple cutaneous mast cell tumors in a Boa constrictor (the snake was euthanized after diagnosis).
  • There are reports of well-differentiated multicentric skin and mucosal mast cell tumors, sometimes with peripheral blood mastocytosis in Green iguanas.
  • There are two reports in tortoises – a Desert tortoise and a Galapagos tortoise. The latter had a cutaneous mass on the neck, which was removed and identified as a cutaneous mast cell tumor. No recurrence was noted after 11 months.
  • However, despite their apparent rarity, mast cell tumors should be considered as a potential differential diagnosis for cutaneous masses in reptiles.

• Worldwide.

• Diagnosis will require fine needle aspiration for cytology Cytology: fine needle aspirate and/or biopsy Biopsy overview for histopathology.
• Treatment is generally surgical excision.
• The owner should be counselled regarding the costs of diagnostic testing plus anesthesia and surgical excision.

• Increased anesthetic risk if concurrent illness, eg systemic disease.

• Mastocytomas, or mast cell tumors, are a type of round cell tumor consisting of mast cells.

• Variable.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Kleinschmidt L M, Reavill D R, Kiupel M et al (2022) Mast cell neoplasia in the Green Iguana, Iguana Iguana. J Zoo Wildl Med 53 (4), 864-869 PubMed.
• Onkels A, Stadler C, Hetzel U et al (2020) Multiple cutaneous mast cell tumours in a Boa imperator. Vet Rec Case Rep 8 (1) VetMedResource.
• Santoro M, Stacy B A, Morales J A et al (2008) Mast cell tumour in a giant Galapagos tortoise (Geochelone nigra vicina). J Compara Pathol 138 (2/3), 156-159 PubMed.
• Reavill D R, Fassler S A & Schmidt & R E (2000) Mast cell tumour in a common green iguana (Iguana iguana). Proceedings of the Association of Reptile and Amphibian Veterinarians, Reno, Nevada ResGate.
• Schumacher J, Bennett R A, Fox L E et al (1998) Mast Cell Tumor in an Eastern Kingsnake (Lampropeltis Getulus Getulus). J Vet Diag Invest 10 (1), 101-104 PubMed.
• Frye F L (1994) Diagnosis and surgical treatment of reptilian neoplasms with a compilation of cases 1966-1993. In Vivo 8 (5), 885-892 PubMed.

Other sources of information

• Reavill D R (2019) Neoplasia. In: BSAVA Manual of Reptiles. 3rd edn. Eds: Girling S J & Raiti P. BSAVA, UK. pp 397-410.