Metastatic diagnosis of canine sternal lymph nodes using computed tomography characteristics: A retrospective cross‐sectional study

Abstract

The accurate evaluation of sternal lymph nodes (StLNs) is critical for the staging of canine thoraco-abdominal tumours. Computed tomography (CT) provides a non-invasive means of assessing StLNs, but its diagnostic accuracy for identifying metastases is unclear. In this retrospective cross-sectional study, we assessed the diagnostic power of various CT measurements. Fifty-seven dogs that underwent concurrent CT and cytological examination of the StLNs were enrolled retrospectively. The size, shape, X-ray attenuation and uniformity of the StLNs were assessed. The dogs were divided into metastasis-negative (n = 21) and metastasis-positive (n = 36) groups. Logistic regression analysis showed that the size (StLN-to-second sternebra ratio [ratio-size]) and precontrast attenuation were significantly different between groups. Combining these parameters achieved a specificity and positive predictive value of 100% (cut-off values: 1.0, 37.5 Hounsfield units, respectively). This suggests that the combination of ratio-size and precontrast attenuation is effective for differentiating metastasis to the StLNs on CT.

CT imaging features of canine thymomas

“…Six cases of lymphadenopathy were noted on CT. Computed tomography provides sensitive evaluation of lymph node size, shape, and attenuation, and previous studies have correlated larger size to the presence of metastasis . In our study, metastasis was confirmed on histopathology in one case of sternal lymphadenopathy, but five other cases of lymphadenopathy did not reveal evidence of metastasis.…”

“…Two of the cases in which there was metastasis present on sternal lymph node biopsy there was no lymphadenopathy noted, suggesting that sternal lymph node biopsies should be considered for more accurate staging. As sternal lymph nodes receive drainage from the thymus through their afferent vasculature, this may be the lymph node to preferentially remove in surgery for histopathologic evaluation for metastasis …”

Survival analysis in dogs with urinary transitional cell carcinoma that underwent whole‐body computed tomography at diagnosis

“…In a previous study, 4 of 137 (3%) dogs were reported to have sternal LN metastasis at necropsy . A recent study also reported that sternal LN metastasis was likely to occur in tumours originating from the urogenital system, including urinary TCC . The present study showed that the median ST in dogs with sternal lymphadenomegaly was only 62 days, thus indicating the importance of evaluating the sternal LNs in addition to the pulmonary area at diagnosis.…”

“…A recent report showed that sternal LN metastasis in dogs with various malignant neoplasms was likely to occur in tumours originating from the urogenital system, including urinary TCC . In that study, 9 out of 25 (36%) cases of cytologically confirmed sternal LN metastasis were from urogenital neoplasms.…”

“…The dogs were considered positive for iliosacral lymphadenomegaly if they met any of the following criteria: the ratio of the maximum dimension of the medial iliac LN to the aorta (measured on a transverse view at the level of the L5‐L6 intervertebral disc space) ≥ 1.3, the ratio of the maximum dimension of the internal iliac LN to the aorta ≥1.0, or the ratio of the maximum dimension of the sacral LN to the aorta ≥1.0 . The dogs were considered positive for sternal lymphadenomegaly if they met both of the following criteria: the ratio of the short‐axis dimension of the sternal LN to the thickness of the second sternebra ≥1.0 and pre‐contrast attenuation of the sternal LN ≥37.5 Hounsfield units . Some of the LNs were sampled through fine‐needle aspiration and subjected to cytological examination according to the clinicians' discretion.…”