Canine Mast Cell Tumors

Flashcards containing terms and definitions about canine mast cell tumors.

Mast Cell Tumors in Dogs

7-21% of all cutaneous canine tumors

Malignant Canine Cutaneous Tumors

11-27% of all malignant canine cutaneous tumors

Mast Cell Tumors-dogs

The MOST COMMON cutaneous tumor in dogs

Mast Cell Tumors-cats

The 2nd MOST COMMON cutaneous tumor in cats

Mastocytosis

Systemic form of mast cell tumors

Typical age of dogs with Mast Cell Tumors

Mean age at presentation = 8-9 years

Breeds Predisposed to Mast Cell Tumors

Boxer, Bull terrier, Boston Terrier, Bulldog

Mast Cell Tumors in pugs

Multiple benign tumors

Mast Cell Tumors in Shar pei

More aggressive

Typical age of cats with Mast Cell Tumors

Mean age also = 8-9 years

Siamese cats

Predisposed to mast cell tumors

Boxers & the “B’s”

Predisposed BUT get lower grade/less aggressive variants

Location of Cutaneous Mast Cell Tumors in Dogs

Trunk (50%), extremities (40%) & head/neck (10%)

Location of Cutaneous Mast Cell Tumors in Cats

Most commonly on head/neck • Pinnae or ear base

Contents of Mast Cell granules

Vasoactive substances (i.e. histamine, leukotrienes, prostaglandins & platelet activating factor)

Darier’s Sign

Disturbance (i.e. physical) of MCT’s can lead to degranulation of mast cells w/ erythema, swelling

GI ULCERS

35%-83% of dogs w/ MCT have some evidence of GI ulceration at necropsy or endoscopy

Gastric acid secretion

Histamine stimulates H2 receptors on gastric parietal cells

Controlling Degranulation (clinically)

Premedication w/ H1 antagonist (diphenhydramine 2 mg/kg IM/PO q 12 hrs PO) to prevent degranulation, anaphylaxis & hypotension during handling

DELAYED WOUND HEALING

Local effects of proteolytic enzymes & vasoactive amines

HYPOTENSION

Histamine & other vasoactive amines released by MCT degranulation

LOCAL HEMORRHAGE

Common after FNA, biopsy & excessive manipulation = Caused by release of heparin from MCT granules

Thoracic Metastasis Evaluation

MCT’s don’t met to lungs

Stage 0 MCT

1 incompletely excised cutaneous MCT

Stage I MCT

1 cutaneous MCT

Stage II MCT

1 cutaneous MCT w/ regional lymph node met

Stage III MCT

Multiple cutaneous MCTs, or a large infiltrative MCT w/ or without LN mets

Stage IV MCT

Any MCT w/ distant mets or BM involvement

Histologic Classification - Cats

Reported types: Mastocytic (more common) Histiocytic

Compact (50 – 90% of cases)

Act benign & can be treated w/ low dose sx = Curative

Diffuse (anaplastic)

Aggressive (like dogs)

Histiocytic-cats

Characterized by histiocyte-like MC’s, potential for regression

Therapy & Prognosis - Cats

Wide excision NOT required since most are compact mastocytic

Splenic/Visceral MCT

Generally good px (MST = 12-19m) w/ splenectomy

Intestinal MCT

Poor px - Most have mets at dx

Grade I MCT in dogs using *Patnaik 3-tier system

No mitotic figures & minimal stromal reaction or necrosis

Grade III MCT in dogs using *Patnaik 3-tier system

Poorly differentiated - Have 3 to 6 mitotic figures/hpf & contain areas of hemorrhage, edema, necrosis & hyalinized collagen

Kiupel 2-tier system *since 2011

Better pathologist agreement & easier to prognosticate

Canine MCT’s – Treatment

Chemotherapy - High risk dog’s (mets or high grade tumor variants)

use vinblastine (mitotic Agent)

Pred/Vinblastine (VBL)

MST 1374 d (3.8 y)

Mast cell tumor (prognostic) panel

Tests for mutation in kit

Age - Prognostic Factors

Older = shorter DFI after RT; Older = short MST after sx

Location – Prognostic Factors

Subungual, oral/perioral (muzzle) & other mm’s associated w/ high-grade tumors & worse px

Stage – Prognostic Factors

Stages 0 -1, confined to skin w/ no mets = have better px compared to higher stage

Size – Prognostic Factors

Tumors >5 cm have shorter survivals

Histologic grade – Prognostic Factors

Well- differentiated usually cured w/ local control vs. NOT w/ more aggressive

Mast Cell Tumor Prognostic Panel What is evaluated?

Mitotic count (MC); AgNOR; Ki67; Ag67; KIT; c-KIT

Alternative Treatment Strategies

Since they occur anywhere ! You will get challenging cases to excise based on size/anatomic location Options? Neoadjuvant chemotherapy or Intralesional chemotherapy

Neoadjuvant Chemotherapy – Practical Application Results

Response rate: 70% - Maximum diameter tumor reduction: 45%

Intralesional Chemotherapy

Inject approximately 1 mg of triamcinolone/cm of tumor

Tigilanol tiglate (Stelfonta)

Approved for all grades of non- metastatic MCT’s in dogs - Injected into primary tumor