Intrathoracic masses (Proceedings)

All diseases known fit into a finite number of etiologies:  Congenital, Degenerative, Developmental, Inflammatory, Metabolic, Miscellaneous, Neoplastic, Toxic, Traumatic, and Unknown.

Lung lobe masses can be caused by one or more disease processes in each of these categories.

Age, breed, sex, history, geographic location, know disease processes all influence the possibilities and probabilities for defining the etiology for a lung mass in the survey radiographic study.

In searching the internet, I found over 15,000 references/articles discussing lung masses in dogs and cats.

The significance of any lesion can be determined most accurately by its biological behavior or its histological characterization-although histological characterization is less accurate than its biological behavior.

Veterinarians usually obtained a “survey radiographic study” to assess thoracic viscera.

When performing the radiographic study, the basic premise should be-I have done all I can with this diagnostic method and have or have not defined a mass lesion-The discussion of how many radiographs should be taken i.e. one, two, three etc. should be left to people with limited thinking capacity.

There are some basic tenants you should remember when doing the radiographic study.  They are:

·         Gas surrounding any soft tissue lesion will allow you to see it better.

·         A lesion in the left lung field is best seen in the right lateral view.

·         A lesion in the right lung field is best seen in the left lateral view.

·         A lesion in the ventral portion of the thorax is best seen in the VD view

·         A lesion in the dorsal portion of the thorax is best seen in the DV view

·         If the animal is anesthetized, it is best to manually inflate the lungs when you take the radiograph.

·         A poor radiographic technique will obscure your ability to see a lesion.

Other imaging methods besides radiology may be required to define lung lesions:

·         CT/CAT imaging is much more accurate at define the size, position, contour and number of lesions.  Masses can often be defined 2-4 months earlier with a CT scan than with conventional radiographic assessment.

·         Endoscopy is much more accurate for defining infiltrative and exophytic lesions in the larynx, trachea and bronchi than conventional radiographic assessment.

·         Pleuroscopy/Thoracoscopy and Mediastinoscopy will become more commonly used in the future since they allow for meaningful assessment and accurate biopsy of lesions that alter the surface of the lung, pleural and mediastinum.

·         Radioactive isotopic labeling of antibodies with subsequent nuclear scanning will be an accurate method of defining lung lesions non-invasively in many disease processes.

·         Direct Visualization-Surgery is sometime required to get a large “chunk” of tissue for analysis or to remove the lesion and send the “whole thing” in for histological characterization and culture.

Biopsy methods are commonly used to obtain tissue for analysis:

·         Tracheobronchial lavage

·         Brush biopsy

·         Fine needle aspirate

·         Core biopsy

·         Surgical biopsy

·         Surgical resection.

There are only seven disease categories

·         Congenital

·         Degeneration

·         Inflammatory

o    Infection

o    Autoimmune

·         Metabolic

·         Neoplastic

·         Toxic

·         Traumatic        

There are only three ways you know what something is:

·         Biological behavior-getting bigger, getting smaller, staying the same

·         Biopsy-fine needle aspirate, core, surgical/wedge

·         Disease specific clinicopathologic testing-immunological or DNA testing

Things to remember

·         Get the know a cytologist/pathologist you can trust to give you the most information from the tissues you submit-never use a cytologist/pathologistwho puts in the report the tissue samples are “not diagnostic”.

·         Don't promise the owners you will have the answer for them “tomorrow”.

·         Don't promise the owners “everything will be all right”.  Some of these animals are going to die either from the disease or your efforts to define the disease.

·         If you are not sure what to do, contact a specialist you have a good workin  relationship with and trust, ask their advice and refer the case especially if you are unsure of how to proceed or you do not have the right equipment to do the study correctly.