Thymoma

Question 1

Thymoma is the ___ most common cranial mediastinal tumor?

Answer 1

2nd

Question 2

Agre distribution for thymoma?

Answer 2

Older patients

Question 3

Two dog breeds affected by thymoma?

Answer 3

38% of 116 dogs w/ thymoma were Labrador and golden retrievers

Question 4

Thymoma is a neoplasm of ____ cells, and commonly include __ and ___

Answer 4

neoplasms of thymic epithelial cell, commonly include mast cells and mature lymphocyte

Question 5

Most common form of thymoma in cats?

Answer 5

Cystic thymoma

Question 6

Metastatic rate in cats with cystic thymoma?

Answer 6

metastasis is rare – but 20% in cats w/ cystic thymoma

Question 7

5 common DDx for mediastinal masses?

Answer 7

lymphoma, ectopic thyroid tumor, brachial cyst and, rarely, sarcomas and metastatic

Question 8

Common findings with PE in an animal with thymoma?

Answer 8

edema of the head, cervical area, and/or thoracic limbs secondary to CVC syndrome

Question 9

What is they % of hypercalemia in dogs with thymoma?

Answer 9

34% of 116 dogs w/ thymoma

Question 10

2 clinical signs that can be noted with thymoma?

Answer 10

megaesophagus and aspiration pneumonia - due to myasthenia gravis (MG)

Question 11

Cytologic samples are accompanied by what other cell types?

Answer 11

cytologic dx of thymoma is confirmed w/ the presence of neoplastic epithelial cells which are accompanied by mast cell and small mature lymphocytes – neoplastic epithelial cells were cytologic evidence in only 61%

Question 12

How can flow cytometry help differentiate thymoma from LSA?

Answer 12

using flow cytometry, thymic lymphocytes can be differentiated from peripheral lymphocytes by their stimultaneous expression of CD4 and CD8 – 10% or more of lymphocytes expressing CD4 and CD8, whereas <2% in lymphomas

Question 13

MST for cats with thymoma treated with surgery alone?

Answer 13

1825 days (5 years)

Question 14

MST for dogs with thymoma treated with Sx alone?

Answer 14

790 d (2.2 yr)

Question 15

another study: MST for dogs treated surgically was 635 days (1.7 yr), significantly better than no Sx (76 days)

Question 16

2 retrospective studies for RT

17 dogs and 7 cats (15-54 Gy): 75% response rate (55% PR, 20% CR), MST: 248 d (dogs) and 720 days (cats)

8 dogs treated hypofractionated RT alone (48-49 Gy, once weekly for 6-7 w): 50% overall RR and 1-y survival rate was 75%

Question 17

The role of chemotherapy in the management of thymomas has not been defined in cats and dogs

a cat achieved a PR after DOX, VCR and L-asparginase

PDs were seen in 9 dogs treated w/ a variety of chemo agents (carbo, DOX, VCR and CYC, etc)

Question 18

Prognostic factors in dogs include?

Answer 18

pre-operative MG and a low % of intratumoral lymphocytes

high % of lymphocytes was associated w/ longer ST

Question 19

long-term survival should be expected for dogs and cats with thymomas that can be completely resected.

Vascular invasion may increase surgical complexity but not necessarily exclude surgery as an option.

RT appears to offer acceptable control rates for those unresectable

Question 20

Comparative Aspects

30% of anterior mediastinal masses in adults and <15% in children

diagnosed in elder patients (>60 yo)

Masaoka staging system:

Stage I: tumor is grossly encapsulated and no capsular invasion is noted microscopically

State II: gross invasion occurs to surrounding fatty tissue or mediastinal pleura. microscopic invasion of the capsule is noted

Stage III: gross invasion into neighboring organs

Stage IVa: pleural or pericardial dissemination

Stage IVb: lymphatic or hematogenous mets

MG is the most common paraneoplastic syndrome associated with thymomas, occurring in 30% to 50% of patients

Complete surgical resection is considered the best predictor for long-term survival for humans with thymomas and is the standard of care in patients with resectable tumors.

RT is indicated most commonly for extensive or recurrent disease

A variety of chemo drugs have been used to treat inoperable thymomas or in cases in which gross residual disease is present after surgery. Cisplatin, ifosfamide, and prednisone are considered the most effective agents