Tumors of the Thoracic Cavity

Question 1

List the presenting complaint and signalment for chest wall tumors

Answer 1

• Middle age (4-6 yrs) large breed dogs
• Hx of owner noticing a firm and fixed thoracic mass
• Non specific CS of discomfort, lameness, resp signs if growing inwardly

(Chest wall tumors v rare in cats)

Question 2

Ddx for chest wall tumors in dogs?

Answer 2

1. OSA (MOST COMMON rib tumor in dogs)
2. Chrondrosarcoma
3. Fibrosarcoma
4. Hemangiosarcoma
4. Mast cell tumor

Question 3

What is the most common rib tumor in dogs?

Answer 3

Osteosarcoma

(Chondrosarcoma 2nd most common)

Question 4

How to work up and stage a chest wall tumor in a dog?

Answer 4

• Open/Wedge Biopsy for definitive diagnosis of OSA vs CSA
• FNA can ID sarcoma but can’t differentiate between OSA or CSA
• Do CT scan prior to surgery

Question 5

Treatment plan for a dog with a chest wall tumor (OSA vs CSA)?

Answer 5

• En bloc excision with chest wall reconstruction and Diaphragmatic advancement (if caudally located)
• Prosthetic mesh implant to fill defect
• Thoracostomy tube placed at wound closure
• If rib OSA → must do surgery + chemo
• If rib CSA → surgical excision usually curable, don’t need chemo

Question 6

How does the treatment plan affect prognosis in dogs with chest wall tumors? (What is the MST)

Answer 6

• Surgical excision + chemo has MST of 1 yr vs surgery alone (6months) for OSA
• CSA can be curable with surgery alone!!! (Must do wedge biopsy to differentiate OSA vs CSA bc of this!)

Question 7

Are lung tumors common in dogs and cats?

Answer 7

Rare in dogs AND cats, usually found incidentally

Question 8

DDx for a lung tumor in dogs vs cats?

Answer 8

Dogs:
1. Bronchoalveolar adenocarcinoma
2. Histiocytic sarcoma

Cats:
1. Bronchial adenocarcinoma

Question 9

What are the presenting complaints and signalment for lung tumors in dogs and cats?

Answer 9

• Usually discovered incidentally
• Possible resp signs
• V/D in cats
• LAMENESS IN CATS!! (Lung digit syndrome)

Question 10

What cancer can metastasize to the digits in cats, resulting in clinical signs of lameness?

Answer 10

Lung tumors!!
(Bronchial adenocarcinoma)

Question 11

How to work up and stage a lung tumor in dogs and cats?

Answer 11

• Rads taken on inspiration

Question 12

How can radiographs help with your DDx list for a lung tumor in a dog?

Answer 12

• Adenocarcinoma rads show well demarcated spherical, solitary mass +/- cavitation
• Histiocytic sarcoma is large, ill defined, irregular, with multiple nodules

Question 13

What are the negative prognostic indicators associated with lung tumors in dogs?

Answer 13

• Small, < 5cm
• Centrally located near hilus (hard to excise)
• If patient is presenting with CS
• If CT staging shows TB LN or pulmonary metastasis
• Histologic score of tumor

Question 14

What are the positive prognostic indicators associated with lung tumors in dogs?

Answer 14

• Small, < 5cm
  - Peripherally located (easier to excise) vs @ the hilus/central
• No evidence of TBLN or pulmonary metastasis

Question 14

What are the prognostic variables associated with lung tumors in cats?

Answer 14

• Histological grade is most important
• Poorly differentiated = 2 months MST
• Well differentiated = 2 years
• Poor px if metastasis to TBLN, pulmonary, or digits
• Poor px if pleural effusion

Question 15

Most likely Ddx for a caudal lung tumor in a cat?

Answer 15

Adenocarcinoma

Question 16

A bernese mountain has multiple tumor like nodules seen on thoracic radiographs. Most likely cause?

Answer 16

Histiocytic sarcoma

Question 17

What breeds are predisposed to histiocytic sarcoma?

Answer 17

- Bernese Mountain Dogs
- Flat coated retrievers

Question 18

Treatment plan for a dog with histiocytic sarcoma localized peripherally on the lung?

Answer 18

Surgical removal + adjunctive CCNU

(only if localized which is uncommon bc metastasis is common)

Question 19

Most common cranial mediastinal tumors in dogs and cats?

Answer 19

• LSA
• Thymoma

Question 20

What diagnostic tests would you perform to work up and stage for a cranial mediastinal tumor?

Answer 20

• CBC/Chem (Thymoma can cause anemia, hypercalcemia)
• Rads
• U/S guided FNA/cytology (small lymphocytes + mast cells = consistent with Thymoma)
• Flow Cytometry to differentiate Lymphoma vs Thymoma

Question 21

Sending out a Flow Cytometry is indicated for work up and staging of what tumor?

Answer 21

Cranial mediastinal tumors (to differentiate Lymphoma vs Thymoma)

Question 22

You receive an FNA/cytology sample from a patient with a cranial mediastinal mass. What are you looking for?

Answer 22

• Small lymphocytes + mast cells is consistent with Thymoma (rather than Lymphoma)

Question 23

How to treat a cranial mediastinal tumor?

Answer 23

• Surgical excision via median sternotomy if possible
• Radiation therapy (if no sx or as adjunct tx)
• Pyridostigmine for MG if thymoma

Question 24

What is the prognosis and MST in dogs and cats treated for thymoma?

Answer 24

• 2 yrs with surgical excision in dogs
• 5yrs with surgical excision in cats (GREAT PROGNOSIS)
• 7 months for dogs with radiation alone
• 2 years for cats with radiation alone

Question 25

Poor prognostic factors associated with thymoma in dogs?

Answer 25

• Younger patient = worse prognosis
• Presence of megaesophagus
• Histologic subtype