Hemangiosarcoma in the Vastus Lateralis Musculature of a Bitch - Sonographic Findings

Abstract

Background: A 10-year-old spayed bitch with hip dysplasia was referred for periarticular ultrasound evaluation. A poorly marginated structure of mixed echogenicity, predominantly hypoechoic, with heterogeneous echotexture, was identified in the vastus lateralis muscle of the right pelvic limb with increased stiffness, assessed using acoustic radiation force impulse (ARFI) elastography, compared to that of the adjacent muscle tissues, and intense vascularization by pulsed Doppler and contrast-enhanced ultrasound (CEUS). Guided biopsy was performed to confirm the diagnosis of hemangiosarcoma. The objective of this study was to describe B-mode ultrasound, CEUS, and ARFI findings of hemangiosarcoma in the vastus lateralis musculature of a dog.

Case: A 10-year-old spayed bitch Golden Retriever weighing 36 kg was evaluated for pelvic limb lameness. The patient presented with bilateral pain during hip extension. The primary diagnostic suspicion was degenerative joint disease and secondary hip dysplasia. The patient was referred for imaging evaluation of the hip joints (radiography and ultrasound) under anesthesia. Right lateral and ventrodorsal projections with the pelvic limbs extended were obtained to confirm the diagnosis. In the right pelvic limb, an amorphous hypoechoic structure with irregular contours and heterogeneous echotexture was observed in the vastus lateralis muscle. In ARFI elastography, it was possible to identify differences in tissue stiffness between healthy and compromised portions. Pulsed-wave Doppler evaluation demonstrated an arterial waveform pattern with a peak systolic velocity of 38.8 cm/s, end-diastolic velocity of 6.9 cm/s, pulsatility index of 1.76, and resistive index of 0.82. CEUS study identified a mean peak of 27.26 %, mean time to peak of 39.95 s, and mean transmission time of 49.96 s. The popliteal lymph node was hyperechoic and heterogeneous in B-mode. In ARFI elastography, the average stiffness was 2.52 m/s, and the CEUS obtained an average peak of 19.98%, average time to peak of 17.52 s, and mean transit time of 22.83 s. Doppler assessment revealed no clear vascularization in the lymph node. Thoracic radiography in 3 projections and abdominal ultrasonography were performed. Radiographic evidence of pulmonary nodules was not observed. On abdominal ultrasound evaluation, it was possible to identify changes in the spleen, which presented with splenomegaly, mixed echogenicity, and heterogeneous echotexture. The animal underwent ultrasound-guided muscle biopsy, which confirmed the presence of hemangiosarcoma in the muscle. The dog was referred for splenectomy and lymphadenectomy of the right popliteal, which confirmed neoplastic involvement of the same neoplasm.

Discussion: On B-mode ultrasound, the observed changes were similar to those in a report of hemangiosarcoma in the muscles of the chest wall in dogs, which contributed to the diagnosis. Although it was only one patient, ARFI elastography results suggest that muscle hemangiosarcoma tends to follow the same elastographic characteristics as malignant lesions in other tissues. Additionally, the popliteal lymph node had a stiffness suggestive of malignancy (mean 2.52 m/s) because it presented a similar result and greater elasticity of metastatic axillary lymph nodes in female dogs (>2.5 m/s) and women (> 1.44 m/s) with breast tumor. With CEUS, it was possible to identify vascularization in the sentinel lymph node that was not visible by pulsed Doppler, and in muscle mass. The findings of this report provided relevant results on muscle hemangiosarcoma in a dog and demonstrated that the information obtained with the association of imaging methods supported the malignancy criteria described in other studies.

Keywords: canine, imaging, diagnosis, neoplasm.