• Cause: malignant neoplasia of the pigment cells in the epidermis, dermis and other sites
• Signs: pigmented, flat or raised, expanding lesion(s) on the skin or mucosa. Evidence of peripheral lymphadenopathy may be present.
• Diagnosis: tissue biopsy for cytological or histopathological examination. Regional lymph node(s) should also be aspirated for cytological examination to rule out metastasis.
• Treatment: surgical excision with wide margins can be curative. Radiation therapy has been described as an adjuvant treatment for local tumor control if complete excision is not possible.
• Prognosis: undetermined due to the low number of published cases. Complete excision of a single, primary cutaneous lesion is generally associated with a fair to guarded prognosis.

• Dark, expanding lesion on the skin or mucosa, may be raised or flat.
• May arise from a pigmented area on the skin or mucosa that had been present and unchanged for a long period of time.

• Acute presentations uncommon.

• None specifically reported for melanoma in the ferret.
• Although broadly speaking, neoplasia occurs more frequently in older animals.

• Tissue biopsy for cytological or histopathological examination for definitive diagnosis is usually readily accessible and relatively inexpensive.
• However, additional diagnostic investigations are usually required to build an adequate database to determine appropriate oncological treatments. These investigations may include hematology, serum biochemistry, urinalysis, diagnostic imaging (radiography, ultrasonography, or CT), and local lymph node aspiration for cytology. Costs can therefore accumulate.
• Radiation therapy and chemotherapy can be costly, and may only be available at tertiary veterinary centers.

• Common sites for metastasis include the regional lymph nodes, lungs, and other visceral organs.
• Pulmonary function can be compromised with lung metastases.

• Malignant neoplasia of the pigment cells in the epidermis, dermis and other sites.
• In mammals, melanocytes are the sole type of pigment cell.
• Exact etiology of melanomas in exotic animals is currently undetermined.
• Proposed mechanisms of oncogenesis include:
  • Ultraviolet (UV) radiation exposure: UVA and UVB:
    • Primarily through environmental sunlight.
    • Initiates DNA damage, stimulates cell-signaling pathways, and induces immune alterations.
  • Genetics: breed and familial clustering of melanoma diagnoses in some domestic animals suggest that genetics may influence the increased frequency of spontaneous mutation in melanocytes in some animals.
  • Environmental carcinogen exposure.

General

• Intense and prolonged exposure to UV radiation.

• Normal melanocytes are dendritic cells derived from neuroectodermal melanoblasts. All chromatophores share a common stem cell of neural crest origin.
• Melanocytes migrate during embryogenesis to the epidermis, dermis, and other sites.
• In non-human mammals, most melanomas are dermal in origin. Cutaneous melanocytes are primarily confined to the hair follicles within the dermis.
• Under normal circumstances, individual melanocytes do not form attachments with other melanocytes but instead, form adherent and regulatory junction with neighboring keratinocytes.
• Melanin is not retained within normal melanocytes. Packaged in melanosomes and transferred through dendritic processes of melanocytes to keratinocytes.
• Conversion of normal melanocytes (that are nonpigmented and isolated from other melanocytes) to pigmented and clustered neoplastic melanocytes is a multistep process:
  • Initiation: generation of mutation within one or more melanocytes.
  • Promotion: proliferation of mutated melanocyte(s) enables amplification of the cell population, persistence of the mutation, and opportunities for additional mutations
  • Transformation: normal suppressors of cell proliferation and activators of apoptosis are superseded by unregulated growth factors, allowing autonomous growth.
  • Metastasis:
    • Detachment of mutated cells from the primary mass.
    • Movement to and through endothelium to travel via blood and/or lymph to a secondary site.

• Oncogenesis typically occurs over a long period (months to years).

• Unknown.
• Reports of melanoma are sporadic.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Otrocka-Domagała I, Paździor-Czapula K, Fiedorowicz J et al (2022) Cutaneous and subcutaneous tumours of small pet mammals – Retrospective study of 256 cases (2014–2021). Animals 12 (8), 965 PubMed.
• Pazzi P, Steenkamp G & Rixon A J (2022) Treatment of canine oral melanomas: A critical review of the literature. Vet Sci 9 (5), 196 PubMed.
• d’Ovidio D, Rossi G & Meomartino L (2016) Oral malignant melanoma in a ferret (Mustela putorius furo). J Vet Dentistry 33 (2), 108-111 PubMed.
• Kanfer S & Reavill D R (2013) Cutaneous neoplasia in ferrets, rabbits, and guinea pigs. Vet Clin North Am Exot Anim Pract 16 (3), 579-598 PubMed.
• Schoemaker N J (2017) Ferret oncology: Diseases, diagnostics, and therapeutics. Vet Clin North Am Exotic Anim Pract 20 (1), 183-208 PubMed.
• Smith S H, Goldschmidt M H & McManus P M (2002) A comparative review of melanocytic neoplasms. Vet Pathol 39 (6), 651-678 PubMed.
• Tunev S S & Wells M G (2002) Cutaneous melanoma in a ferret (Mustela putorius furo). Vet Pathol 39 (1), 141-143 PubMed.
• Ha L, Noonan F P, De Fabo E C & Merlino G (2005) Animal models of melanoma. Proc J Invest Derm Symp 10 (2), 86-88 PubMed.

Other sources of information

• Bergman P J (2020) Melanoma. In: Clinical Small Animal Internal Medicine. Ed: David B. Wiley-Blackwell, USA. pp 1347-1352.
• Williams B H & Wyre N R (2020) Neoplasia in Ferrets. In: Ferrets, Rabbits and Rodents – E-Book: Clinical Medicine and Surgery. Eds: Quesenberry K, Mans C, Orcutt C & Carpenter J W. Elsevier, USA. pp 92-108.