Contributors: Laura Garrett, Rosanna Marsella, Susan North, David Scarff

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Second most common site for feline tumors.
  • Skin tumors in cats make up 20-30% of all tumors.
  • Less common than in dogs.
  • Fewer different types occur but higher percentage is malignant. Malignant skin tumors in cats are reported to be three times more common than benign tumors.
  • Relative frequency of various skin tumors has been reported to be changing with fibrosarcoma becoming more common than epithelial skin tumors.
    Follow the diagnostic algorithm for the investigation of a Feline cutaneous mass Feline cutaneous mass.

Presenting Signs

  • Skin mass of variable appearance depending on site and type.
  • Solitary or multiple.

Incidence

  • Approximately 20-30% of all feline tumors.
  • Main tumors are basal cell tumor, squamous cell carcinoma, fibrosarcoma and mast cell tumor.

Epithelial

  • Basal cell carcinoma - common.
  • Squamous cell carcinoma - common.
  • Papilloma - rare.
  • Adnexal.
    • Modified apocrine/ceruminous.
    • Apocrine/sweat gland - uncommon.
    • Sebaceous - rare.
    • Hair matrix/follicle - rare.
    • Perianal - rare.

Mesenchymal

  • Fibrosarcoma - common.
  • Fibroma - rare.
  • Lipoma/liposarcoma - uncommon.
  • Hemangioma/hemangiosarcoma - uncommon.
  • Malignant fibrous histiocytoma - rare, except for vaccine-associated.

Mastocytoma

  • Mast cell tumor - common.

Melanoma

  • Melanocytic tumor - uncommon to rare.

Multiple masses

  • Mast cell tumor - common.
  • Cutaneous lymphoma -uncommon.
  • Metastatic skin lesions - uncommon.
  • Squamous cell carcinoma (solar) - common in certain areas (high altitude).
  • Mycosis fungoides - rare.

Age Predisposition

  • Older cats (9-10 years).

Breed Predisposition

  • No breed predilection overall (Siamese Siamese - less affected with squamous cell carcinoma and more affected with mast cell tumors).

Pathogenesis

Etiology

Specific

  • Squamous cell carcinoma - white hair on face, common sites pinna  Squamous cell carcinoma: pinna 01 , nasal planum  Squamous cell carcinoma: nasal planum - pre-radiotherapy .
  • Fibrosarcoma - commonly at injection sites.

Pathophysiology

  • Primary mass may cause problems if very large or becomes ulcerated, secondarily infected or is at an irritating site, eg eyelid Eyelid and conjunctiva: neoplasia.
  • If malignant, may spread to local lymph nodes and/or distant sites.
  • Primary mass may cause problems, ie impair limb movement if very large or becomes ulcerated, secondarily infected or is at an irritating site, eg eyelid  Squamous cell carcinoma: eyelid 01 - tabby  white DSH 12 years . May be erosive or disfiguring.
  • If malignant, may spread to local lymph nodes and/or distant sites.

Diagnosis

Presenting Problems

  • Solitary or multiple skin masses.
  • If masses become ulcerated, they may develop infections.
  • Solar squamous cell carcinoma can appear as scab  Solar: actinic - dermatitis 01 and develops to an erosive lesion  Solar: actinic - dermatitis 02 rather than a mass.

Client History

  • New mass or masses noticed in skin.
  • Slow or rapid growth reported may have had previous mass at same site - recurrence.
  • Typically no pain is associated with it.
  • Pruritus can be present with some tumors (eg mast cell tumors) or if infection develops.

Clinical Signs

  • Solitary or multiple skin masses.
  • Well circumscribed, mobile, slow growing, pigmented - suggests benign.
  • Poorly defined, adherent, rapid growth - suggests malignant.
  • May be ulcerated, erosive and secondarily infected lymph node enlargement possible.

Diagnostic Investigation

Cytopathology

  • Fine needle aspirate  Fine-needle aspirate of primary mass for cytology (and lymph nodes if enlarged).
  • If mast cell tumor is suspected, premedication with antihistamines should be considered before fine needle aspirate.

Histopathology

  • Incisional, core or punch biopsy Biopsy: skin of primary mass for histopathology.
  • Excisional biopsy of a representative lesion if multiple skin masses.

Radiography

Gross Autopsy Findings

  • Solitary - abscess Abscess.
  • Inflammatory reaction.
  • Eosinophilic granuloma Eosinophilic granuloma complex.
  • Multiple - drug reaction Drug eruption  Drug eruption: due to FeLV vaccination .
  • Other skin disease.
  • Local/drainage lymph node enlargement if malignant.
  • Secondary mass/masses in other organs if malignant.

Histopathology Findings

  • Variable according to tumor type.
  • Will show degree of invasion, cell differentiation, etc and distinguish benign/malignant.

Treatment

Standard Treatment

Solitary mass

  • Wide surgical excision if possible try to make diagnosis before surgery.
  • Radiotherapy Radiotherapy for some tumors (mast cell tumors/carcinomas/sarcomas) depending on site and ability to excize.
  • Highly proliferative tumors (eg fibrosarcomas) should be followed by radiotherapy whenever possible. 

Multiple masses

  • Combined surgery and radiotherapy for some solitary tumors depending on site.
  • Combined surgery and chemotherapy for some malignant tumors.
  • Immunotherapy with cells (eg VERO cells) genetically modified to produce cytokines is a novel and prosing approach for highly malignant tumors.

Subsequent Management

Monitoring

  • Regular clinical examination to check for local recurrrence and lymph node metastasis +/- radiography to check for distant metastasis.

Outcomes

Prognosis

  • Variable according to tumor type.
  • Grave for metastatic disease.

Expected Response to Treatment

Reasons for Treatment Failure

  • Not possible to treat because too extensive, or no effective therapy available, eg mycosis fungoides.
  • Local recurrence due to inadequate excision.
  • Distant metastasis.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Miller M A, Nelson S L, Turk J R et al (1991) Cutaneous neoplasia in 340 cats. Vet Pathol 28 (5), 389-395 PubMed.
  • Bostock D E (1986) Neoplasms of the skin and subcutaneous tissues in dogs and cats. Brit Vet J 142 (1), 1-19 PubMed.
  • Susaneck S J (1983) Feline skin tumors. Compend Contin Educ 5 (4),  251-258 VetMedResource.
  • Macy D W & Reynolds H A (1981) The incidence, characteristics and clinical management of skin tumors of cats. JAAHA 17 (6), 1026-1034 VetMedResource.
  • Scott D W (1980) Feline Dermatology 1900-1978: a monograph. JAAHA 16 (3), 331-459 VetMedResource.

Other sources of information

  • Guaguere E & Prelaud P (1999) A practical guide to feline dermatology.Merial.
  • Carpenter J L, Andrews L K and Holzworth J (1987) Tumors and Tumor-like lesions. In: Diseases of the Cat. Medicine and Surgery. Ed J Holzworth. Philadelphia: W B Saunders Co. pp 406-596.
  • Vail D M and Withrow S J (1996) Tumors of the skin and subcutaneous tissues. In: Small Animal Clinical Oncology. Eds S J Withrow and E G MacEwen. 2nd edition. Philadelphia: W B Saunders Co. pp 167-191.

Other Sources of Information