Case Study

CT – thoracic soft tissue mass, likely thymoma, in a 11 year old FS Collie

This 11 year old FS Collie dog has a history of megaesophagus and myasthenia gravis

DX

The CT findings are compatible with a thymoma and suggest the esophageal dysmotility to be paraneoplastic in origin.

Image Interpretation

CT of the thorax – There is a soft tissue attenuating cranioventral mass lesion of 4.5 x 3 x 2.5 cm with
well-defined margins. The mass is directly adjacent to the heart but appears to be
separate from the heart. No major vessel or tracheal displacement is noted. The precardial intrathoracic esophagus reveals moderate dilation with gas. There is a hypoattenuating and hypoenhancing nodule of 5 mm diameter within the
right medial liver lobe adjacent to the gallbladder.No dilation
is noted level with the heart and for the caudal thoracic esophagus.

Outcome

Thymic lymphoma, ectopic thyroid or parathyroid carcinoma and other are all possible,
but by far less likely differential diagnoses. The liver lesion is compatible with a small uncomplicated liver cyst. Benign nodular
hyperplasia or a secondary neoplasia is by far less likely. If further definition is
warranted ultrasound guided sampling would be ideal.