Mast cell tumour

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  • Less common than dog but 15% of all feline tumors.
  • Cutaneous and visceral forms.
  • Diagnosis : cytology, histopathology.
  • Treatment : surgical excision, radiotherapy, chemotherapy.
  • Prognosis : cutaneous: good; visceral: poor.


  • Histological grading not prognostic unlike in dog.
  • Two forms:
    • Typical like dog and
    • Histiocytic majority are behaviorally benign.


  • Splenic, intestinal usually malignant - associated with widespread dissemination/metastasis.
  • Often mast cell leukemia (buffy coat mastocytosis) with splenic form. Occasionally cutaneous and visceral forms occur together.


Clinical signs

  • Solitary or multiple skin nodules, well-circumscribed, dome-shaped, alopecic, raised, +/- erythema, ulceration. Purple   →   Dark-red in color.
  • Suspicious mass or splenomegaly on abdominal palpation.Variations must always assess for systemic/visceral involvement, even with solitary, small dermal mass.
  • Occasional peritoneal effusion.
  • Local lymph node enlargement possible (uncommon).


Differential diagnosis



  • Cutaneous form : good.
  • Visceral form : poor for intestinal.
  • Can be reasonable (approx 1 year) for splenic form following clinical signs of malaise, anorexia etc. despite bone marrow involvement if splenectomy has been performed (median 2 months otherwise).

Expected response to treatment

  • Removal of all visible or palpable tumor.
  • Decrease in peripheral mastocytosis.

Reasons for treatment failure

  • Local recurrence or metastasis of malignant tumors to local lymph nodes or distant sites (less than 20% metastasize).
  • Previously undetected visceral or systemic involvement.


  • Dissemination to distant sites after treatment or widespread metastasis at time of diagnosis, hence treatment not possible.
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