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==Classification==
*Although metastatic pulmonary tumours are common in the lung, primary pulmonary tumours are relatively rare in domestic animals (cf. humans)
*However, primary tumours are more common in dogs and cats than in other animals
*Classification of pulmonary tumours can be difficult due to the [[General Pathology - Disorders of Cell Growth#Metaplasia|metaplasia]] which can occur in both inflammation and in neoplasia
**Bronchial papilloma
**Bronchial adenoma/ carcinoma (arising from major airways)
**Bronchioloalveolar adenoma/ carcinoma (arising from small airways or alveolar parenchyma - either secretory bronchiolar cells or type II epithelial cells)
**Carcinoid: in humans, these tumours arise from neuroendocrine cells - rare in animals
==Primary tumours==
[[Image:Pulmonary carcinoma.jpg|right|thumb|100px|<small><center>Pulmonary carcinoma and emphysema (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:Adenomatosis of lung.jpg|right|thumb|100px|<small><center>Adenomatosis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:Alveolar cell carcinoma.jpg|right|thumb|100px|<small><center>Alveolar cell carcinoma (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Most arise from pulmonary epithelium
*Usually middle aged to old dogs and cats
===Bronchogenic carcinoma===
* In dogs usually invasive bronchogenic carcinomas mostly arising from hilar region an metastasise via the airways to other parts of the lungs
*Types:
**Squamous cell - large cells with vesicular nuclei
**Adenocarcinoma - invasive and destructive, least malignant
**Adenosquamous carcinoma - both squamous and glandular part in one tumour, common, similar to metastatic
**Undifferentiated - very rare in animals
*Large, irregular, pale, not well defined border
*Spread through pulmonary lymphatics
===Bronchioloalveolar tumours===
*Most common in dogs
*Arise from either secretory bronchiolar or alveolar type II epithelial cells, often both types in same tumour
*May be an incidental necropsy finding
*Often occur as solitary nodules at the periphery of the lung, occasionally multiple
*Histologically:
**Regular alveolar pattern
*May resemble chronic inflammation or rapid metastatic spread of tumour from a primary elsewhere in the body
===Sheep pulmonary adenomatosis (SPA/ Jaagsiekte)===
*Also called '''pulmonary carcinomatosis'''
*Infectious [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchiolar]]-[[Lungs - inflammatory#Infectious causes of pneumonia|alveolar]] carcinoma caused by a [[Retroviridae|retrovirus]]
*Commonest under intensive management systems which favour aerosol transmission and close contact of disease
*Behaves like chronic pneumonia
*Takes months to years to express itself clinically as coughing and exercise intolerance
*Gross pathology:
**Heavy lungs which fail to collapse
**The lesions progress from small firm grey/white nodular lesions to extensive confluent areas with replacement by neoplastic tissue
**Cut surface oozes fluid
**There is often coexistent infection present
**Occasional metastases to bronchial and mediastinal lymph nodes can occur
*Histopathology:
**Widespread proliferation of alveolar (Type 2) and terminal bronchiolar epithelium, lining the alveoli and lower airways
**Multiple neoplastic foci of cuboidal/columnar cells forming papillary projections into the lumen
**Metastases of the same in the bronchial and mediastinal lymph nodes
*There is no serological test, and diagnosis depends upon raising the animal by the hind limbs whereupon a clear fluid issues from the nose = "Wheelbarrow test"
===Carcinoids===
*Occasionally occur in animals, mainly in humans
*Originate from neuroendocrine components of major airways
*Microscopically:
**Large number of small secretory granules
===Granular cell tumours===
*Also called '''myoblastomas'''
*Mesenchymal origin
*Occurs in [[Hindgut Fermenters - Horse - Anatomy & Physiology|horses]]
*Grossly:
**Multiple discrete of partially confluent nodules
**Tend to be associated with major bronchi
**May cause obstruction
*Histologically:
**Large polyhedral cells aggregation
**Fibrovascular stroma
===Lymphomatoid granulomatosis===
*Occurs in dogs
*Histologically:
**Mixed, atypical lymphoreticular cells infiltrating one or more lung lobes
**Tend to invade blood vessel walls and airways
**Fibrous stroma
**Many mitotic figures
==Metastatic tumours==
[[Image:Lung carcinoma.jpg|right|thumb|100px|<small><center>Lung carcinoma in a dog (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:Metastatic fibrosarcoma.jpg|right|thumb|100px|<small><center>Metastatic fibrosarcoma in canine lung (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:Metastatic sweat gland carcinoma.jpg|right|thumb|100px|<small><center>Metastatic sweat gland carcinoma in feline lung (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*All are malignant by definition
*Relatively common in domestic species
*Examples of common metastatic tumours include :
**Mammary carcinoma (dog and cat)
**Haemangiosarcomas
**[[Bones - hyperplastic and neoplastic#Osteosarcoma (OSA)|Osteosarcomas]]
**Uterine adenocarcinoma (cattle)
**Malignant melanoma (horse)
*Often manifest as multiple nodules scattered throughout the parenchyma - these lesions are often referred to as "cannon-ball" metastases, in all lung lobes
*Histological examination usually shows the metastases to resemble the primary tumour however they may be either better or less well differentiated
*Sometimes the metastasis can be sen only microscopically, grossly the lungs are discoloured and more firm than usual
*Disseminate widely through lymphatics
*'''In horses'''
**cranial mediastinal lymphosarcoma
**pulmonary granular cell tumour
**malignant melanoma
**haemangiosarcoma
**metastatic adenocarcinoma
**metastatic carcinoma
<big>A space occupying lesion in the canine lung may produce periosteal thickening of the long bone - [[Bones - hyperplastic and neoplastic#Hypertrophic osteopathy|'''Hypertrophic Osteopathy''']]</big>