Laryngeal rhabdomyoma in a dog

By Emma Scurrell

Biopsies taken from a mass protruding into the lumen of the larynx in a 12-year-old crossbreed dog with a history of increased upper respiratory noise.

Fig 1. The mass is a neoplasm composed of large polygonal cells that have large amounts of eosinophilic cytoplasm and single vesicular nuclei with often prominent nucleoli, typical of rhabdomyoblasts.

Fig 2. Occasional elongate strap cells with cross striations are identified within the neoplastic tissue.

Fig 3. A closer view of the strap cells with cross striations similar to those seen in myofibres.

Final Diagnosis

Laryngeal rhabdomyoma

Discussion

These are uncommon tumours of skeletal muscle but when they occur in the dog, they most commonly occur in the larynx. They typically protrude into the larynx and some may display low grade locally infiltrative behaviour. The presence of well-differentiated neoplastic cells, limited invasiveness and a low mitotic rate support a benign tumour and the low number of reported cases suggest a benign clinical course with regards to local recurrence and metastatic disease.