Comparison of computed tomographic images of normal cranial and upper cervical lymph nodes with corresponding E12 plastinated-embedded sections in the dog

To document normal lymph nodes on computed tomographic images, 102 scans were reviewed of dogs that had computed tomography (CT) of the head and upper cervical region. If lymph nodes were identified, symmetry, density, homogeneity, and size, as well as the relation to the surrounding fat tissue were noted. CT images with distinct asymmetric, enlarged, and obliterated lymph nodes were excluded. To improve the detailed anatomical topography, corresponding E12 plastinated-embedded sections of a dog were used. Compared with muscle tissue, normal lymph nodes were slightly hypodense and had a homogeneous parenchyma. Mandibular and retropharyngeal lymphocentres could be seen consistently and CT proved to be a useful method both to detect their presence and to assess their morphology. It was not possible to identify the parotid lymph node consistently because of the lack of tissue contrast at the lymph node-gland interface.     

Comparison of B-mode and Doppler ultrasonographic findings with histologic features of benign and malignant superficial lymph nodes in dogs

OBJECTIVE: To compare and correlate B-mode and color Doppler ultrasonographic characteristics with histopathologic findings of benign and malignant superficial lymph nodes in dogs. STUDY POPULATION: 50 superficial lymph nodes that were normal, abnormally large on physical examination, or represented regional lymph nodes draining an area of suspected primary malignancy in 30 dogs. PROCEDURES: Before excision, lymph nodes were evaluated via B-mode and color Doppler ultrasonography to assess size, echogenicity, presence of a hilus, acoustic transmission, and vascular flow. Formalin-fixed, paraffin-embedded tissue sections of excised lymph nodes were stained with H&E and examined for the presence and extent of necrosis, fibrosis, fat, metastases, and tissue heterogeneity. To assess vascularity, the number and distribution of vessels stained by the Verhoeff van Gieson technique were recorded. RESULTS: In superficial lymph nodes, a varied echogenicity corresponded to tissue heterogeneity. The ultrasonographic detection of a hilus was associated with the presence of fibrous tissue, fat, or both in the hilar region. Acoustic enhancement corresponded to presence of areas of intranodal necrosis. There was significant correlation between both the distribution and the number of vessels detected via ultrasonography and that detected by histopathology. The amount of flow estimated via ultrasonography was typically higher than that estimated via histologic examination. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that histopathologic changes in canine lymph nodes have associated ultrasonographic changes and suggest that lymph node ultrasonography has an important role in the evaluation of lymph nodes in dogs in general and in dogs with neoplastic disease in particular.     

FEASIBILITY OF CONTRAST‐ENHANCED ULTRASOUND‐GUIDED BIOPSY OF SENTINEL LYMPH NODES IN DOGS

Our goal was to develop and validate a technique to identify the sentinel lymph nodes of the mammary glands of healthy dogs with contrast‐enhanced ultrasound, and evaluate the feasibility of obtaining representative samples of a sentinel lymph node under ultrasound guidance using a new biopsy device. Three healthy intact female adult hounds were anesthetized and each received an injection of octafluoropropane‐filled lipid microspheres and a separate subcutaneous injection of methylene blue dye around a mammary gland. Ultrasound was then used to follow the contrast agent through the lymphatic channel to the sentinel lymph node. Lymph node biopsy was performed under ultrasound guidance, followed by an excisional biopsy of the lymph nodes and a regional mastectomy procedure. Excised tissues were submitted for histopathologic examination and evaluated as to whether they were representative of the node. The ultrasound contrast agent was easily visualized with ultrasound leading up to the sentinel lymph nodes. Eight normal lymph nodes (two inguinal, one axillary in two dogs; two inguinal in one dog) were identified and biopsied. Lymphoid tissue was obtained from all biopsy specimens. Samples from four of eight lymph nodes contained both cortical and medullary lymphoid tissue. Contrast‐enhanced ultrasound can be successfully used to image and guide minimally invasive biopsy of the normal sentinel lymph nodes draining the mammary glands in healthy dogs. Further work is needed to evaluate whether this technique may be applicable in patients with breast cancer or other conditions warranting evaluation of sentinel lymph nodes in animals.     

Diffusion weighted magnetic resonance imaging is a feasible method for characterizing regional lymph nodes in canine patients with head and neck disease

In dogs diagnosed with solid tumors, regional lymph node involvement or evidence of distant metastasis can predict worse prognoses and significantly decreased survival. Lymph node size alone has been shown to be insufficient as a predictor for the accurate clinical staging of some canine neoplasia. However, certain regional lymph nodes (including those of the oral cavity) are difficult to access for routine tissue sampling. Diffusion weighted magnetic resonance imaging (MRI) has demonstrated the ability to differentiate metastatic from inflammatory/benign lymph nodes in clinical studies with human cancer patients through the calculation of quantitative values of diffusion termed apparent diffusion coefficients (ADC). The objective of this prospective, exploratory study was to evaluate diffusion‐weighted MRI and ADC as potential methods for detecting metastatic lymph nodes in dogs with naturally occurring disease. We hypothesized that diffusion‐weighted MRI would identify significantly different ADC values between benign and metastatic lymph nodes in a group of canine patients with head or neck disease. Our study population consisted of eight client‐owned canine patients, with a total of 20 lymph nodes evaluated (six metastatic, 14 benign). Our results demonstrated that two of four observers identified a significant difference between the mean ADC values of the benign and metastatic lymph nodes. When data from all four observers were pooled, the difference between the mean apparent diffusion coefficients values of the benign and metastatic lymph nodes did not reach significance (P‐value = 0.0566). Findings indicated that diffusion‐weighted MRI is a feasible method for further characterizing enlarged lymph nodes in dogs with head and neck disease, however measured ADC values did not differ for benign vs. metastatic lymph nodes in this small sample of dogs.     

Association between lymph node size and metastasis in dogs with oral malignant melanoma: 100 cases (1987-2001)

OBJECTIVE: To determine the association between lymph node size and metastasis and to assess measurement of lymph node size as an accurate and reliable means of tumor staging in dogs with oral malignant melanoma. DESIGN: Retrospective study. ANIMALS: 100 dogs with histologically confirmed oral malignant melanoma. PROCEDURE: Clinical records for dogs with oral malignant melanoma were reviewed. Data regarding size and results of cytologic or histologic examination of lymph nodes were evaluated. The association between lymph node size and metastasis was determined. RESULTS: Forty-seven (47%) dogs, of which 23 (49%) had enlarged mandibular lymph nodes, had no cytologic or histologic evidence of metastasis. Of 53 (53%) dogs with cytologic or histologic evidence of mandibular lymph node metastasis, 37 (70%) had enlarged mandibular lymph nodes, and 16 (30%) had mandibular lymph nodes of normal size. Overall, 16 of the 40 (40%) dogs with normal-sized lymph nodes had microscopic evidence of metastatic disease. Sensitivity and specificity of lymph node size as a predictor of metastasis were 70 and 51%, respectively, and the positive and negative predictive values were 62 and 60%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Although a significant relationship was identified between lymph node size and metastasis to the lymph node, this association did not appear strong enough to be clinically relevant. Results suggest that lymph node size alone is insufficient for accurate clinical staging of oral malignant melanoma in dogs; cytologic or histologic examination of regional lymph nodes should routinely be performed, regardless of size of those nodes.     

Lymph node staging of oral and maxillofacial neoplasms in 31 dogs and cats

A retrospective study was performed to report the histologic examination results of regional lymph nodes of dogs and cats with oral or maxillofacial neoplasms. Twenty-eight dogs and 3 cats were evaluated. Histologic examination results of standard and serial tissue sectioning of regional lymph nodes were recorded. When available, other clinical parameters including mandibular lymph node palpation, thoracic radiographs, and pre- and postoperative fine needle aspiration of lymph nodes were compared with the histologic results. Squamous cell carcinoma, fibrosarcoma, and melanoma were the most common neoplasms diagnosed in dogs. Squamous cell carcinoma and fibrosarcoma were diagnosed in cats. Of the palpably enlarged mandibular lymph nodes, 17.0% had metastatic disease histologically. Radiographically evident thoracic metastatic disease was present in 7.4% of cases. Preoperative cytologic evaluation of the mandibular lymph node based on fine needle aspiration concurred with the histologic results in 90.5% of lymph nodes examined. Postoperative cytologic evaluation of fine needle aspirates of regional lymph nodes concurred with the histologic results in 80.6% of lymph nodes examined. Only 54.5% of cases with metastatic disease to regional lymph nodes had metastasis that included the mandibular lymph node. Serial lymph node sectioning provided additional information or metastasis detection. Cytologic evaluation of the mandibular lymph node correlates positively with histology, however results may fail to indicate the presence of regional metastasis. Assessment of all regional lymph nodes in dogs and cats with oral or maxillofacial neoplasms will detect more metastatic disease than assessing the mandibular lymph node only.     

Frequency of an accessory popliteal efferent lymphatic pathway in dogs

Staging and therapeutic planning for dogs with malignant disease in the popliteal lymph node are based on the expected patterns of lymphatic drainage from the lymph node. The medial iliac lymph nodes are known to receive efferent lymph from the popliteal lymph node; however, an accessory popliteal efferent pathway with direct connection to the sacral lymph nodes has also been less frequently reported. The primary objective of this prospective, anatomic study was to describe the frequency of various patterns of lymphatic drainage of the popliteal lymph node. With informed client consent, 50 adult dogs with no known disease of the lymphatic system underwent computed tomographic lymphography after ultrasound‐guided, percutaneous injection of 350 mg/ml iohexol into a popliteal lymph node. In all 50 dogs, the popliteal lymph node drained directly to the ipsilateral medial iliac lymph node through multiple lymphatic vessels that coursed along the medial thigh. In 26% (13/50) of dogs, efferent vessels also drained from the popliteal lymph node directly to the internal iliac and/or sacral lymph nodes, coursing laterally through the gluteal region and passing over the dorsal aspect of the pelvis. Lymphatic connections between the right and left medial iliac and right and left internal iliac lymph nodes were found. Based on our findings, the internal iliac and sacral lymph nodes should be considered when staging or planning therapy for dogs with malignant disease in the popliteal lymph node.     

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.     

Clinical,cytologic, and histologic features of a mammary micropapillary carcinoma in a dog

Mammary invasive micropapillary carcinoma is a rare variant of mammary carcinoma that was recently recognized in dogs. The cytologic features and biologic behavior of such neoplasms in dogs have not yet been widely discussed in the veterinary literature. We report the clinical, cytologic, and histologic features of a canine micropapillary carcinoma in a 13‐year‐old female mongrel dog. The mammary region presented with extreme local pain, severe edema and erythema, and multifocal epidermal ulceration, which is typical for an inflammatory mammary carcinoma. Fine‐needle aspirates were highly cellular and consisted of individual cells and papillary cell clusters with characteristics of malignant epithelial cells. Histologic examination revealed neoplastic cells arranged in small papillae without fibrovascular cores, sometimes inside clear lymphatic spaces, indicating lymphovascular invasion. Regional lymph node evaluation revealed metastatic cells. Due to deteriorating clinical condition the dog was euthanatized 5 months after mastectomy. At necropsy, metastatic neoplastic mammary cells were found in popliteal and mediastinal lymph nodes, the right femoral biceps muscle, liver, heart, lungs, and urinary bladder.     

SONOGRAPHIC CHARACTERISTICS OF PRESUMPTIVELY NORMAL CANINE MEDIAL ILIAC AND SUPERFICIAL INGUINAL LYMPH NODES

The medial iliac and superficial inguinal lymph nodes are not routinely palpable in the dog, and ultrasound imaging provides an alternate noninvasive technique to assess these lymph nodes, as well as to guide needle aspiration. Herein we describe the ultrasound characteristics of the medial iliac and superficial inguinal lymph nodes in 50 healthy dogs, as well as frequency and ease of node detection. The relationship between the size of the lymph nodes and the following variables was assessed: age, gender, body weight, body condition score, body length, and thoracic height and width. Right and left medial iliac lymph nodes were detected in 50 (100%) dogs, right superficial inguinal lymph node(s) in 49 (98%) dogs, and left superficial inguinal lymph node(s) in 47 (96%) dogs. In >90% of both sets of lymph nodes, the echogenicity was hypoechoic or isoechoic to surrounding tissues, with a corticomedullary or homogenous echotexture, smooth, clearly defined margins, and a fusiform shape. Increasing weight, distance from the sternal manubrium to the ischium, and thoracic height and width were associated with increased lymph node size (P‐values<0.05). Average lymph node sizes and range of sizes provide preliminary reference values for the medial iliac and superficial inguinal lymph nodes in normal dogs.     

ULTRASONOGRAPHIC EXAMINATION OF CERVICAL MASSES IN THE DOG AND CAT

The ultrasonographic appearance of clinically undifferentiated neck masses for which a definitive diagnosis was eventually obtained in nineteen dogs and one cat is presented in this report. Multiple lesions were seen ultrasonographically in 4 dogs and no cervical abnormalities were seen in 2 dogs resulting in 22 lesions in 20 annuals. Of 7 benign lesions, there were 2 patients with reactive lymph nodes from a regional inflammatory process, and 1 patient each with primary pyogranulomatous lymphadenitis, arteriovenous malformation, foreign body granuloma, cellulitis, and hematoma. Of 15 malignant lesions, 7 were thyroid carcinomas, 3 were lymphomas with submandibular and cervical lymph node enlargement, 3 were lymph node enlargements associated with regional metastasis of malignant tumors, one was a leiomyosarcoma and one was a carotid body tumor. One dog with a diffuse soft tissue swelling of the ventral cervical region had only slight asymmetry of the thyroid lobes on ultrasound examination and no abnormalities of the neck at post mortem. A second dog examined with ultrasound 4 months after surgical removal of a carotid body tumor had no evidence of tumor recurrence. Ultrasonographic examination provided information regarding the character of the lesions, the tissue or organ of origin, and invasion into other anatomic structures. Ultrasound examination in conjunction with fine needle or tissue biopsy provided a definitive diagnosis in those animals in which biopsies were performed.     

Magnetic resonance imaging of canine mast cell tumors

Mast cell tumors (MCT) are the most common cutaneous tumors in dogs. Our purpose was to describe the magnetic resonance (MR) imaging characteristics of cutaneous MCT and to identify imaging characteristics that allow differentiation of metastatic from normal lymph nodes. Eight dogs with a total of nineMCT were imaged as were their presumed draining and associated contralateral lymph nodes. The signal intensity of tumors and lymph nodes was compared to adjacent musculature. On T2-W images, 7/9 MCT were hyperintense to muscle and 2/9 were isointense. On T1-W images, 8/9 MCT were isointense and 1/9 were mildly hypointense. All tumors were strongly contrast enhancing; 5/9 were homogeneous and 4/9 heterogeneous in their enhancement patterns. Six lymph node pairs were included in the evaluation (five sentinel lymph nodes with metastases, one without, and six contralateral lymph nodes). Metastatic lymph nodes were significantly larger than their contralateral lymph nodes (P = 0.039). All lymph nodes were isointense on T1-W images and hyperintense on T2-W images. 5/5 metastatic and 2/7 normal lymph nodes were heterogeneously T2-hyperintense. All lymph nodes were moderately to strongly contrast enhancing. 4/5 metastatic and 2/7 normal lymph nodes had heterogeneous enhancement patterns. While heterogeneity was more common in metastatic than in normal lymph nodes, this difference was not significant (P = 0.058 for T2-W images; P = 0.234 for postcontrast images). MR imaging may be useful in the presurgical evaluation and clinical staging of cutaneous MCT.     

COMPUTED TOMOGRAPHIC CHARACTERISTICS OF PRESUMED NORMAL CANINE ABDOMINAL LYMPH NODES

Though identification of lymph nodes is essential in staging cancer patients, little has been reported about the CT features of canine abdominal lymph nodes. The purpose of this retrospective study was to describe the visibility, location, and characteristics of abdominal lymph nodes in abdominal CT studies of dogs considered unlikely to have lymphadenopathy. The relationship between the number of identified lymph nodes and intraabdominal fat ranking, body weight, and slice thickness was also investigated. A total of 19 dogs were included. At least two jejunal lymph nodes and both left and right medial iliac lymph nodes were identified in all dogs. Colic lymph nodes were not identified in any of the dogs. Visualization of all other lymph nodes varied. There were significantly more lymph nodes visible in dogs with more intraabdominal fat (P < 0.0001). No correlation between the number of identified lymph nodes and body weight (P = 0.64) or slice thickness (P = 0.76) was found. Though most of all identified lymph nodes had an elongated shape, a rounded shape was most common in splenic, pancreaticoduodenal, renal, ileocolic and caudal mesenteric lymph nodes. Most lymph nodes had a homogeneous structure before and following the intravenous administration of contrast medium. Some lymph nodes had a slightly irregular structure or were relatively more hyper attenuating in the periphery than centrally before and/or after contrast administration. Mean attenuation before contrast was 37 Hounsfield Units (HU) (range 20–52 HU), and 109 HU after contrast (range 36–223 HU). Findings indicated that the CT visibility, characteristics of different abdominal lymph nodes may be variable in dogs.     

Quantitative assessment of mast cells and expression of IgE protein and mRNA for IgE and interleukin 4 in the gastrointestinal tract of healthy dogs and dogs with inflammatory bowel disease

OBJECTIVE: To characterize the mucosal IgE network in dogs affected with inflammatory bowel disease (IBD) and compare it with that for healthy dogs. ANIMALS: 9 healthy dogs and 20 dogs with IBD. PROCEDURE: In situ hybridization of mRNA specific for IgE and interleukin 4 (IL-4) and immunohistochemical analysis for IgE protein and 2 markers of mast cells (ie, tryptase and chymase) were performed on tissue sections obtained from the gastrointestinal (GI) tract and lymph nodes of dogs. RESULTS: Dogs with IBD had significantly more cells positive for IgE protein and more mast cells in the GI mucosa than healthy dogs. Despite this significant increase in number of cells positive for IgE, cells positive for IgE mRNA were rarely detected in the GI mucosa; most cells positive for IgE mRNA were found in mesenteric lymph nodes. Signal pattern of IL-4 mRNA was similar to that of IgE mRNA. CONCLUSIONS AND CLINICAL RELEVANCE: The increased numbers of cells positive for IgE and mast cells in dogs with IBD suggest hypersensitivity such as hypersensitivity to bacterial or dietary-derived antigens in the intestinal lumen. Future studies need to elucidate whether this represents a cause of inflammation or is a result of the inflammatory process of IBD.     

Ultrasonography of the medial iliac lymph nodes in the dog

Sixty-one medial iliac lymph nodes of 38 different dogs (eight with adenocarcinoma of the apocrine glands of the anal sac, 13 with multicentric lymphoma, six with multicentric lymphoma but in clinical remission, and 11 control dogs) were evaluated to assess the ability of ultrasound to identify and interrogate these lymph nodes across the different groups and to differentiate these groups using different sonographic parameters. Ultrasound proved to be useful to assess canine medial iliac lymph nodes. An increase in size or number of detected lymph nodes or finding rounder or heterogeneous lymph nodes could differentiate lymph nodes of dogs of the control group from lymph nodes of dogs with lymphoma or an adenocarcinoma of the apocrine glands of the anal sac. Subcategories of malignancy could not be differentiated. More studies need to be performed, both with patients with reactive lymph nodes and also focusing on other canine superficial lymph nodes, before generalizing the results of this study to other areas or diseases.     

Measurement of estrogen receptors in normal and neoplastic lymph node tissue from dogs.

Estrogen receptors were measured in normal canine lymph nodes and neoplastic tissue from dogs with lymphoma, using a commercially available [3H]estradiol dextran-coated charcoal assay. Using the same assay, estrogen receptors were detected in the positive-control tissues--dog uterus, rat uterus, and lyophilized bovine uterus. Specific binding of [3H]estradiol was not detected in rat skeletal muscle or in any of the canine lymphoid tissues, indicating that the specimens did not contain estrogen receptors.     

Indirect computed tomography lymphangiography with aqueous contrast for evaluation of sentinel lymph nodes in dogs with tumors of the head

Sentinel lymph node evaluation is widely used in human medicine to evaluate the first lymph node(s) to which a tumor drains. Sentinel lymph node biopsy allows avoidance of extensive lymphadenectomies in cases where the sentinel lymph node is negative for metastasis, thereby reducing patient morbidity. It has been shown that regional lymph nodes are not always the sentinel lymph node, thus identification and sampling of sentinel lymph nodes allows for more accurate staging, which is critical for treatment and prognostication in dogs with cancer. The objective of this prospective, pilot study was to determine if indirect computed tomography (CT) lymphangiography with aqueous contrast agent would successfully allow identification of sentinel lymph nodes in dogs with masses on the head. Eighteen dogs underwent CT lymphangiography. The sentinel lymph node was successfully identified within 3 min of contrast injection in 16 dogs (89%). Compression of lymphatic vessels from endotracheal tube ties and/or the patient's own body weight delayed or prevented identification of sentinel lymph nodes in two dogs (11%). Computed tomography lymphangiography with aqueous contrast can be used successfully to rapidly identify sentinel lymph nodes in dogs with masses on the head.