Thymoma Flashcards
Thymoma is the ___ most common cranial mediastinal tumor?
2nd
Agre distribution for thymoma?
Older patients
Two dog breeds affected by thymoma?
38% of 116 dogs w/ thymoma were Labrador and golden retrievers
Thymoma is a neoplasm of ____ cells, and commonly include __ and ___
neoplasms of thymic epithelial cell, commonly include mast cells and mature lymphocyte
Most common form of thymoma in cats?
Cystic thymoma
Metastatic rate in cats with cystic thymoma?
metastasis is rare – but 20% in cats w/ cystic thymoma
5 common DDx for mediastinal masses?
lymphoma, ectopic thyroid tumor, brachial cyst and, rarely, sarcomas and metastatic
Common findings with PE in an animal with thymoma?
edema of the head, cervical area, and/or thoracic limbs secondary to CVC syndrome
What is they % of hypercalemia in dogs with thymoma?
34% of 116 dogs w/ thymoma
2 clinical signs that can be noted with thymoma?
megaesophagus and aspiration pneumonia - due to myasthenia gravis (MG)
Cytologic samples are accompanied by what other cell types?
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%
How can flow cytometry help differentiate thymoma from LSA?
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
MST for cats with thymoma treated with surgery alone?
1825 days (5 years)
MST for dogs with thymoma treated with Sx alone?
790 d (2.2 yr)
another study: MST for dogs treated surgically was 635 days (1.7 yr), significantly better than no Sx (76 days)
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%
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)
Prognostic factors in dogs include?
pre-operative MG and a low % of intratumoral lymphocytes
high % of lymphocytes was associated w/ longer ST
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
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
