TVT

Question 1

Canine TVT is ____ transmitted ____ tumor of dogs?

Answer 1

horizontally, infectious histiocytic tumor of dogs

Question 2

Canine TVT is spread by ____ but also ___, ____, _____?

Answer 2

coitus, but it may also be spread by licking, biting, and sniffing tumor-affected areas

Question 3

Prevalence of TVT is highest in what locations?

Answer 3

prevalence is highest in tropical and subtropical areas

southern United States, Central and South America, southeast Europe, Ireland, Japan, China, the Far East, the Middle East, and parts of Africa

Question 4

Who is at risk with TVT?

Answer 4

sexually intact mature dogs

Question 5

Commonly affected site for TVT?

What other 4 sites can be affected?

Answer 5

external genitalia

but other sites that can be affected through licking or sniffing include the nasal and oral cavities, SQ tissues, and the eyes

Question 6

When does tumor growth appear after mating?

Answer 6

Tumor growth generally appears on the external genitalia or nasal or oral mucosa within 2 to 6 months of mating

Question 7

Metastatsis occurs in what % of cases?

Common sites of metastasis?

Answer 7

TVT usually remains localized, but metastasis occurs in up to 5% to 17% of cases to draining regional LN (i.e., inguinal, iliac, tonsils), SQ tissue, skin, eyes, oral mucosa, liver, spleen, peritoneum, hypophysis, brain, and BM

Question 8

TVT is a round cell tumor of what origin?

Answer 8

histiocytic

Question 9

IHC expression for TVT?

Answer 9

IHC expression of vimentin, lysozyme, alpha-1-antitrypsin (AAT), and macrophage-specific ACM1, as well as negative IHC staining specific for other cell types

Question 10

The course of disease is divided into 3 phases?

Answer 10

progressive phase (P) in which the tumor grows for 3 to 6 months, then a short stationary phase (S), which is followed by a regressive phase (R) in most dogs

Question 11

When does spontaneous regression start?

Answer 11

spontaneous regressions usually start within 3 months after implantation but rarely after 9 mo of tumor

Question 12

What occurs during the P phase?

Answer 12

Initially, in the P phase, the tumor downregulates its MHC class I β2-microglobulin and class II expression

allows it to evade the host’s histocompatibility barrier (T-cell cytotoxicity)

high concentration of tumor- secreted transforming growth factor-β1 (TGF-β1) inhibits tumor MHC antigen expression and NK cell activity

Question 13

TVT can target and damage what cells?

Answer 13

dendritic cells

Question 14

What occurs late in P phase?

Answer 14

late in the P phase, marked increase in immune cell infiltration occurs and tumor-infiltrating lymphocytes (TILs) produce high concentrations of the proinflammatory cytokine IL-6, which acts synergistically with host-derived IFNγ to antagonize the immunoinhibitory activity of TGF-β1 and results in MHC expression in up to 40% of tumor cells and restores NK cytotoxicity

Question 15

What triggers the R phase?

Answer 15

a critical threshold level of IL-6 secreted by TILs has to be reached to trigger TVT into R phase

after progressive growth for 3 to 4 mo, the tumor spontaneously regresses with upregulation of MHC antigen expression possibly under epigenetic control

regression has been correlated w/ upregulation of genes involved w/ inflammation and chemotactic cytokines

Question 16

What should be evaluated in animals with TVT?

Answer 16

Regional LN for metastasis (15%)

Question 17

Treatmet for TVT?

What is the RR?

Answer 17

Single-agent vincristine (0.5 to 0.7 mg/m2 IV, once weekly for 3 to 6 tx) obtains a complete and durable response in 90% to 95% of treated dogs.

Question 18

Treatment for resistant TVT cases?

Answer 18

Resistant cases can be treated with DOX (25 to 30 mg/m2 IV, every 21 days for 3 tx)

Question 19

Recurrence rate for TVT following Sx?

Answer 19

however, overall recurrence rate of 30% to 75%.

tumor transplantation into the surgical wound by contamination from instruments or gloves may also cause postoperative tumor recurrence.