The Importance of Ultrasonography in the Evaluation of Mammary Tumors in Bitches

Abstract

The high incidence of mammary tumors in small animals is concerning. Patient history, clinical examination, physical evaluation, and imaging studies are important for clinical staging. Ultrasonography is commonly applied to investigate the presence of abdominal metastasis. However, it has been shown to provide important information regarding mammary tumors' architecture and advanced sonographic techniques can provide information regarding neovascularization, stiffness, and perfusion. Different techniques have been investigated to determine accuracy to predict the lesions' histological classification. This paper reviews the information regarding each sonographic technique in the evaluation of mammary tumors, describing the most common findings and their potential to accurately assess and predict malignancy. Even though the gold standard for the diagnosis of mammary lesions is the histopathological examination, some ultrasonographic features described can predict the potential of a lesion being malignant. Among the different sonographic techniques, elastography can be considered the most reliable modality to accurately differentiate benign from malignant tumors when malignant lesions present increased stiffness. However, the combination of all sonographic techniques can provide important information that can lead to a better therapeutic approach and clinical staging. Furthermore, the potential of the sonographic study, especially CEUS to monitor therapeutic progression, demonstrate the need of further studies.

Keywords: angiogenesis; canine; diagnostic imaging; elasticity imaging techniques; neoplasms; perfusion.

Figure 1

B-mode ultrasonography of mammary tumors in bitches. (A) a small oval hypoechoic mammary nodule is seen between electronic calipers, presenting circumscribed margins. (B) a small elongated hypoechoic mammary mass is seen between electronic calipers, with slightly irregular margins. (Frequency: 14 MHz; Depth: 2.8 cm).

Figure 2

Ultrasound image of a malignant mammary tumor in a bitch, using triplex Doppler assessment (B-mode, color-coded doppler, and pulsed-wave doppler -triplex; increased velocities -systolic peak velocity (VSM); and end-diastolic velocity (VDF)-indicate malignancy. Sample volume = 0.5/2 mm.

Figure 3

Ultrasound image of a malignant mammary tumor in a bitch. (A) B-mode image, demonstrating heterogeneous echotexture and mixed echogenicity, with solid and liquid components; (B) image of the ARFI elastography assessment of the same patient, obtaining the elastogram and shear velocity of the mass—note the presence of increased stiffness both in the elastogram (see scale on the right side of the image) and in the values obtained for the shear velocity (chart below and on the right).

Figure 4

Contrast-enhanced ultrasound image of mammary neoplasms in bitches. (A1,A2) Grade III solid mammary carcinoma—note the difference in vascularity seen on color-coded Doppler (A1) and perfusion seen on CEUS (A2); Grade II mixed tumor mammary carcinoma (yellow arrows)—(B1) mammary nodule on color Doppler, with absence of neovascularization detected by this method and in (B2) presence of tissue perfusion detected by CEUS.