CLINICAL AND MAGNETIC RESONANCE IMAGING FEATURES OF INFLAMMATORY VERSUS NEOPLASTIC MEDIAL RETROPHARYNGEAL LYMPH NODE MASS LESIONS IN DOGS AND CATS

Lymphotropic nanoparticle magnetic resonance imaging for diagnosing metastatic lymph nodes in dogs with malignant head and neck tumours

Lymphotropic nanoparticle magnetic resonance imaging (LNMRI) utilises ultrasmall paramagnetic iron nanoparticles (USPIOs) for imaging of metastatic lymph nodes in patients afflicted with cancer. LNMRI has been shown to be a highly effective and accurate way to diagnose metastasis in humans but has not been commonly reported on in veterinary medicine. USPIOs are phagocytised by macrophages and then localised to lymph nodes where they create a susceptibility artefact on gradient echo MRI sequences. In this study dogs (n = 24) with naturally occurring head and neck tumours were imaged with LNMRI then had mandibular and retropharyngeal lymph nodes extirpated for histological analysis. Subjective and objective analysis of the LNMRI images was performed and imaging results compared to histology as the gold standard. A total of 149 lymph nodes were included in this study. The overall sensitivity, specificity and accuracy was 64%, 94.4% and 89.3% respectively. However, if dogs with mast cell tumours were excluded from analysis the sensitivity, specificity and accuracy rose to 85.7%, 95.7% and 94.6%. LNMRI is potentially an accurate way to determine the presence of lymph node metastasis in dogs with some types of head and neck tumours. However, LNMRI has only moderate accuracy in dogs with oral or mucocutaneous mast cell tumours in this region.

Retrospective characterisation and outcome of surgical treatment for cervical lymph node abscessation in 15 dogs

CASE HISTORIES

Medical records of a private referral hospital (Veterinary Emergency Clinic, Toronto, Canada) and a university teaching hospital (Louisiana State University, Baton Rouge, LA, USA) were reviewed, using the search terms lymphadenectomy, lymph node extirpation, cervical lymphadenitis, and lymph node abscessation. Dogs (n = 15) with a diagnosis of cervical lymph node abscessations confirmed through histopathology that underwent surgery for treatment from January 2015-May 2022 were included in the study. Long-term follow-up data was obtained by an in-person visit or telephone interview with each owner. Dogs that met the inclusion criteria were of various breeds with a median age of 6 (min 0.5, max 12) years. All cases presented with cervical swelling and lethargy, with inappetence and fever in 5/15 dogs. The range of duration of clinical signs prior to treatment was 1-3 weeks. Seven dogs were treated with a short course of antibiotics, with or without prednisone, without successful resolution, before referral.

CLINICAL FINDINGS

Diagnostic imaging using CT or cervical ultrasound revealed enlargement of unilateral mandibular and retropharyngeal lymph nodes with regional cellulitis and oedema in four dogs, enlargement of unilateral retropharyngeal lymph nodes with regional cellulitis in eight dogs, and a right ventral cervical abscess infiltrating the right medial retropharyngeal lymph nodes with oedema in one dog. Unilateral or bilateral cervical lymph node abscessation was diagnosed by lymphadenectomy and histopathology of affected lymph nodes. Bacterial cultures from samples of excised lymph nodes were positive in six cases.

TREATMENT AND OUTCOME

Cervical exploration and lymphadenectomy were performed in all cases. Thirteen dogs received antibiotics along with surgical treatment. Resolution was defined as absence of cervical swelling or enlarged lymph node(s) at the time of long-term follow-up (median 300 (min 240, max 1,072) days). Most patients had resolution of clinical signs following surgical excision of affected lymph nodes. Two dogs had complications including recurrence of clinical signs and development of open wounds following surgery. Their clinical signs resolved following additional administration of antibiotics.

CONCLUSIONS AND CLINICAL RELEVANCE

All dogs in this series had lymphadenectomy of abscessed lymph nodes and showed resolution of clinical signs with a favourable outcome. As 13/15 dogs also received antibiotics in conjunction with surgical treatment, appropriate use of antimicrobials may also play a role in treatment of this disease process.

Lymph Node Abscessation Secondary to Neoplasia in Two Dogs

A 5-year-old male neutered mixed breed dog and an 8-year-old female spayed golden retriever presented for cervical swelling which was later diagnosed as abscessation of the retropharyngeal lymph node with a malignant round cell tumor and carcinoma with multifocal squamous differentiation, respectively. In veterinary medicine, there is limited published information regarding abscessation of lymph nodes secondary to a neoplastic process. While more common in humans, there are only limited case reports available. Advanced imaging (computed tomography), cytology, surgical excision, and histopathology lead to the final diagnosis. Both dogs underwent surgical extirpation of the lymph nodes and adjuvant chemotherapy protocols. Six weeks postsurgical excision, dog one was euthanized due to quality-of-life concerns. The second dog successfully completed 18 treatments of radiation therapy and was still alive at 388 days postsurgical excision. At the time of manuscript submission, the second dog was doing well clinically.

Computed tomography features of presumed normal mandibular and medial retropharyngeal lymph nodes in dogs

Computed tomographic (CT) features of lymph nodes are used for diagnosis, staging, and response evaluation in veterinary patients. The objectives of this study were to describe maximum short- and long-axis transverse diameters (SATD and LATD, respectively), volume, and attenuation of presumed normal canine mandibular lymph nodes (MLNs) and medial retropharyngeal lymph nodes (MRLNs), to investigate the effect of variables on these features, and to describe inter-observer reliability of transverse diameter and attenuation measurement. Computed tomography studies of 161 dogs were retrospectively reviewed. Median values for SATD were 5.2 and 5.4 mm, median values for volume were 0.26 and 0.54 cm³, and median values for attenuation were 32.3 and 31.8 Hounsfield units (HU) for MLN and MRLN, respectively. Median LATD was 11 mm for MLNs. Height of the first cervical vertebra (HCV1) and weight were positively associated with transverse diameters of both MLNs and MRLNs (P < 0.001). Grade of dental disease was negatively associated with transverse diameters of both MLNs (P = 0.001) and MRLNs (P < 0.03). The intraclass correlation coefficient (ICC) was 0.94 [95% confidence interval (CI): 0.94 to 0.95] for transverse diameter measurement. This study provides descriptive data on the CT characteristics of presumed normal MLNs and MRLNs in dogs and describes a highly reliable method of measuring transverse diameter.

Computed tomographic findings and clinical features in dogs with canine cutaneous lymphoma: 10 cases (2007-2018)

OBJECTIVE

To report clinical features, CT findings, treatment protocols, and outcomes for dogs in which canine cutaneous lymphoma (CCL) was diagnosed.

ANIMALS

10 client-owned dogs with CCL.

PROCEDURES

Medical records of dogs in which a diagnosis of CCL had been made between September 2007 and July 2018 and in which CT had been performed prior to treatment were reviewed. All available CT studies were reviewed, and an anatomical reference system was developed to map observed lesions. Treatment protocols and patient outcomes were summarized.

RESULTS

14 CT examinations were performed on the 10 dogs, and 9 dogs had lesions consistent with CCL on CT images. Nodular lesions were present in 8 dogs, and cutaneous or subcutaneous mass lesions were seen in 3. Well-defined, diffusely distributed, contrast-enhancing, cutaneous or subcutaneous nodules were most common; mass lesions were more variable in appearance. Nine dogs had lymphadenopathy, with the mandibular and axillary lymph nodes most commonly affected. Four dogs had confirmed nodal involvement, and 4 had confirmed visceral involvement. Nine dogs received treatment with chemotherapy, and 5 had a complete response.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that dogs with CCL may have a wide spectrum of CT findings. Many of these lesions, including affected lymph nodes, would be unlikely to be detected clinically, suggesting that CT may be a useful modality to assess the severity of disease and for guiding selection of local versus systemic treatment.

Semi-quantitative strain elastography may facilitate pre-surgical prediction of mandibular lymph nodes malignancy in dogs

Evaluation of mandibular lymph nodes in a patient with head and neck cancer is important for stage determination and prognosis development, and, in human medicine, the use of sonoelastography for differentiating between non-metastatic and metastatic lymph nodes has been reported. Our prospective, cross-sectional study aimed to evaluate the diagnostic performance of strain elastography and to determine elastographic cut-off values for predicting malignancy. Sixty-six mandibular lymph nodes were included (clinical healthy, n = 45; non-metastatic, n = 8; and metastatic, n = 13). Elastographic images were evaluated qualitatively (elastographic pattern) and semi-quantitatively (mean hue histogram and stiffness area ratios). Elastographic patterns were classified as grades 1 to 4, according to the percentage of high elasticity determined by visualization. The mean hue histogram was defined based on as the mean pixel color values within the lymph node. Stiffness area ratios were determined by computer program analysis of the stiff area. Among the criteria, receiver operating characteristic curve analyses revealed cut-off values for the prediction of malignancy of 92.26 for mean hue histogram (sensitivity: 100%, specificity: 92%), and 0.17 for stiffness area ratios (sensitivity: 86%, specificity of 100%). Reproducibility and repeatability were excellent. In conclusion, semi-quantitative evaluation via strain elastography holds potential for predicting lymph node malignancy.