Sonographic Assessment of the Normal and Abnormal Feline Mammary Glands and Axillary and Inguinal Lymph Nodes

Abstract

Ultrasound has been used as a diagnostic tool in normal mammary glands and mammary tumors of several species. This study aims to describe the B-mode and Doppler ultrasound features of the mammary glands and draining lymph nodes in 32 adult female cats. Group 1 (G1) consisted of 22 cats without changes in the mammary glands. The average age was 45 ± 25.09 months, where 63.6% (n = 14) were neutered and 31.8% (n = 7) had received progestin at some point for reproductive control. Mammary gland structure was predominantly hypoechoic and homogeneous, with well-defined margins. The average thickness was 1.52 ± 1.59 mm, although it may be affected by estrus, pregnancy, and lactation. In G1, 100% of lymph nodes were homogeneous, 98% were hypoechoic, and 100% were with well-defined margins and hilar vascularization. Group 2 (G2) consisted of 10 cats with mammary nodules. The average age was 88.8 ± 40.5 months, and 70% were intact and all had already received progestin. Ultrasound demonstrated enlarged mammary glands, with nodules of different textures clinically, mainly affecting the abdominal mammary glands (61%). In 33.33%, there were visible mammary ducts. Only 54.17% were homogeneous, 95.83% were hypoechoic, and the margins were regular in 52.08%. Lymph nodes in abnormal mammary chains may present changes in size, shape, echotexture, and echogenicity. Ultrasound examination of the mammary glands and lymph nodes are possible to evaluate the entire mammary chain as well the superficial inguinal and axillary lymph nodes for abnormalities in the feline.

Figure 1

B-mode mammary gland ultrasound (between markers) of healthy cats during anestrus, at late pregnancy, and during lactation. (a) Right caudal thoracic mammary gland with homogeneous echotexture, hypoechoic parenchyma, and well-defined margins. (b) Right caudal abdominal mammary gland with homogeneous echotexture, hypoechoic parenchyma, and less distinct margins. (c) Left caudal abdominal mammary gland with heterogeneous echotexture, slightly hypoechoic parenchyma (comparing to superficial tissue), and the presence of anechogenic mammary ducts (arrows). Cr: cranial. Frequency = 15 MHz.

Figure 2

B-mode mammary ultrasound (between markers) of cats with mammary tumors during anestrus. (a) Left caudal abdominal mammary gland with hypoechoic parenchyma, poorly defined margins, and uneven edges. (b) Right cranial abdominal mammary gland with heterogeneous echotexture, uneven shape, unclear edges, and the presence of several lobulations. (c) Left caudal abdominal mammary gland with anechoic content and hypoechoic intratumoral sediment and well-defined margins, creating acoustic enhancement (AE). Cr: cranial. Frequency = 15 MHz.

Figure 3

B-mode ultrasound of lymph nodes in a two-year-old cat with abnormal mammary glands and a three-year-old cat with normal mammary glands. (a) Right superficial inguinal lymph node (between the markers) of rounded shape and heterogeneous echotexture, without the central hyperechogenic line. (b) Left superficial inguinal lymph node (between markers) with oval shape, hypoechoic parenchyma, and homogeneous echotexture, with the central hyperechogenic line. (c) Right axillary lymph node (between markers) with elongated oval aspect, homogeneous echotexture, and hypoechoic parenchyma, without central hyperechogenic line. Cr: cranial. Frequency = 15 MHz.