13-Year-Old FS Mixed Breed Dog

Signalment & History

A 13 year old FS mixed breed dog presents with a 1 month history of vomiting and decreased appetite.

On physical examination, decreased lung sounds on the left side was ausculted.

Left lateral thorax Right lateral thorax VD thorax


There is an area of increased soft tissue opacity present within the caudal subsegment of the left cranial lung lobe. Some of the features include: Uniform soft grey tissue with rounded margins, border effacement of the pulmonary vessels, air bronchograms, lobar sign, and (in this case, discrete) border effacement of the cardiac silhouette.

The body wall, pleural space and cardiovascular structures are within normal limits.


This lesion is most consistent with a pulmonary neoplasm. The soft tissue opacity has convex margins and is distorting the caudal margin of the caudal subsegment of the left cranial lung lobe.

  • Histiocystic sarcoma are rare round cell tumors
  • They have a strong breed predilection for Bernese Mountain Dogs, Rottweilers and Retrievers
  • They can be localized or disseminated throughout the body (including liver, spleen, GIT and musculoskeletal system [including the spine])
  • Histiocystic sarcomaare aggressive tumors that metastasize readily and rapidly
  • Most common thoracic radiographic findings with HS are the presence of a pulmonary mass and intrathoracic lymphadenopathy
  • Histiocystic sarcomahave a predilection for the right middle lung lobe (not this case!) (unlike other primary pulmonary neoplasias which commonly occur in the caudal lobes)


Tsai et al (2011) Imaging characteristics of intrathoracic histiocytic sarcoma in dogs. Vet Rad and Ultrasound 53(1), 21-27