Pulmonary carcinoma
From Felipedia
Contents |
Introduction
Primary lung tumors are rare in cats and account for < 1% of all tumors. The mean age is approximately 11-12 years. There is no breed predilection and females appear over-represented. No significant research has proven an association with FeLV infection. Adenocarcinomas account for 70% to 80% of primary pulmonary neoplasia in cats; less common carcinomas include squamous cell carcinomas and adenosquamous carcinomas. Fibrosarcomas, osteosarcomas, chondrosarcomas, hemangiosarcomas, lymphomatoid granulomatosis (angioinvasive T-cell lymphoma), histiocytic sarcoma, and adenomas are other primary neoplasms that have been documented in feline lungs.
Metastasis of primary lung tumors in cats can occur to other areas of the lungs, or to the long bones, liver, spleen, pancreas, kidneys, adrenal glands, heart, brain, oesophagus, abdominal or mediastinal lymph nodes, eyes, or digits in cats.
Most cats with pulmonary neoplasia are middle-aged or geriatric. Presenting signs can include cough, exercise intolerance, dyspnea, lameness (from metastasis or hypertrophic pulmonary osteopathy, the latter more common in dogs than in cats), weight loss, anorexia, and lethargy. Diagnosis is usually established based on radiographs, cytologic examination, and histopathologic examination.
Cats that present with firm soft tissue masses should have metastatic pulmonary neoplasia added to the list of differential diagnoses.
Types of Lung Tumors
- carcinomas are the most common primary lung tumor in cats
- carcinomas are subclassified according to their location (i.e., bronchial, bronchoalveolar, and alveolar)
- bronchial carcinomas are more common (76%) than either bronchoalveolar or alveolar carcinomas
- bronchial adenocarcinom (ADC) is the most common lung tumor in cats (66%-71%)
- bronchoalveolar ADC, anaplastic carcinoma, and SCC account for 10%-15% of lung tumors
- 8% of primary pulmonary carcinomas are grade I, 23% grade II, and 69% of carcinomas are grade III
Metastasis
- 75% metastatic rate for primary lung tumors in cats
- regional lymph node involvement in 29%-35% and distant metastasis in 46%-58%
- distant metastatic sites include pleural cavity in 65% and extrathoracic sites in 35%
- metastasis to multiple digits presenting as swelling of ≥ 1 toes and lameness without respiratory signs is a common primary complaint
- weight-bearing digits and 3rd phalanx are most commonly affected in cats
•amputation is not palliative due development of further digit lesions and progressive non-respiratory disease
Histology of digital metastases
- Most common metastatic tumor in the cat
- One or more digits may be involved
- Bone lysis evident on histopathology and radiographic examination of the digits
- Invasion of the dermis, subcutaneous tissue and third phalanx by neoplastic epithelium arranged in solid islands, nests, and glandular structures
- Short papillary proliferations may extend into the glandular lumina
- Neoplastic epithelium often evokes a proliferation of fibroblasts
- Aggregates of epithelial cells vary in thickness from one to several layers
- Focal squamous differentiation may be found
- Majority of the cells have an abundant amount of eosinophilic cytoplasm with basally located ovoid, euchromatic nuclei
- Cilia may be present on the neoplastic cells
Clinical Signs
Primary pulmonary tumours are not considered as common in cats as metastatic tumours. Interestingly, cats often do NOT present with clinical signs referable to the presence of the lung tumour (cough, dyspnoea). Instead they present for signs of metastic disease, with variations on which is now commonly referred to as the lung digit syndrome.
- non-productive coughing, exercise intolerance, and other respiratory signs (i.e., dyspnea and tachypnea)
- systemic signs include lethargy and weight loss
- peracute presentation for hemothorax, pneumothorax, or malignant pleural effusion is uncommon
Paraneoplastic Syndromes
A paraneoplastic syndrome has been reported in cats, involving hypertrophic osteopathy and hypercalcemia of malignancy. Endogenous lipid (cholesterol) pneumonia has been associated with bronchogenic carcinoma in 1 cat[1].
Diagnosis
Thoracic Radiographs
- lung tumors have a variable radiographic appearance in cats, with 3 main presentations:
- mixed bronchoalveolar pattern (33%)
- ill-defined alveolar mass (22%)
- pulmonary mass with cavitation (56%)
- bronchial disease is common in cats with primary lung tumors
- caudal lung lobes are most commonly affected
- diffuse lesions are present in 24%-53% cats
- uncommon findings: multiple or miliary lesions, hilar lymphadenopathy, and pleural effusion
Treatment
Surgical Management
- lateral thoracotomy (4th-6th intercostal) for small to medium-sized lung tumors and hilar lymph node biopsy
- median sternotomy for large tumors and inspection of other lung lobes, but lymph node biopsy is more difficult
- lymph node aspirate or biopsy is recommended as neoplastic infiltration may not be clinically apparent
- partial lobectomy can be performed for peripheral tumors, but complete lung lobectomy preferred
- lobectomy can be performed with either stapling equipment or individual ligatures
Chemotherapy
- systemic chemotherapy may offer some benefit
- intracavitary chemotherapy ± sclerosing agents (i.e., talc or tetracycline) have been used for malignant effusions in cats but with limited resposnes.
Prognosis
Usually poor.
