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Prevalence, location and concurrent diseases of ultrasonographic cyst-like lesions of abdominal lymph nodes in dogs
  1. A. Liotta, DVM, MSc, PhD, DipECVDI1,
  2. F. Billen, DVM, MSc, PhD, DipECVIM-CA2,
  3. M. Heimann, DVM, DipECVDP3,
  4. A. Hamaide, DVM, PhD, DipECVS4,
  5. M. Rizza, DVM1,
  6. A. L. Etienne, DVM, MSc, PhD1 and
  7. G. Bolen, DVM, MSc, PhD, DipECVDI1
  1. 1Division of Diagnostic Imaging, Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
  2. 2Division of Small Animal Internal Medicine, Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
  3. 3ANAPET sprl, rue du Faubourg 269, Montigny-le-Tilleul B-6110, Belgium
  4. 4Division of Surgery, Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
  1. E-mail for correspondence: g.bolen{at}ulg.ac.be

Abstract

Lymph nodal cyst-like lesions are occasionally identified during abdominal ultrasound in dogs. However, a study evaluating their prevalence and clinical significance is lacking. The aim of this observational cross-sectional study was to evaluate prevalence, most common location and concurrent diseases of cyst-like lymph nodes detected during abdominal ultrasound. Affected lymph nodes, patient signalment and concurrent diseases of dogs with cyst-like lymph nodal lesions having undergone abdominal ultrasound over a one-year period were recorded. Twenty-three affected lymph nodes were observed in 17/553 dogs (prevalence=3 per cent). The most commonly affected was the lumbar lymphocenter (7/23), followed by the coeliac (6/23), the cranial mesenteric (5/23) and the iliosacral (5/23). Twenty-three concurrent diseases were diagnosed in 17 dogs, among which 16/23 were non-neoplastic (70 per cent). The most common concurrent disease was renal insufficiency (8/23), followed by neoplasia (7/23), gastroenteropathy (3/23), benign prostatic disease (2/23), pancreatitis (1/23), peritonitis (1/23) and neurological disease (1/23). No statistical correlation existed between cyst-like lymph nodal lesion and a specific neoplastic or non-neoplastic disease. In conclusion, in the present study, cyst-like lymph nodal lesions have a low prevalence, involve different lymphocenters and were found in dogs affected by different diseases, including both non-neoplastic and neoplastic aetiologies.

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Various ultrasonographic patterns have been identified in abdominal lymph nodes of clinically healthy adult dogs and puppies (Nyman and O'Brien 2007, Agthe and others 2009, Stander and others 2010, Krol and O'Brien, 2012). Lymph nodes may have either a homogeneous hypoechoic or isoechoic pattern, or a corticomedullary distinction with a hypoechoic rim surrounding the hyperechoic central rim, or a heterogenous aspect with a hypoechoic nodule (Nyman and O'Brien 2007, Agthe and others 2009, Mayer and others 2010, Stander and others 2010, Krol and O'Brien 2012). Many different ultrasonographic features have been studied to differentiate benign from malignant lymph nodes. Malignancy has been significantly associated with an increased number of detectable lymph nodes and a rounded shape (Llabrés-Díaz 2004), with heterogeneity (Llabrés-Díaz 2004, Kinns and Mai 2007), with a maximal short and long axis ratio (De Swarte and others 2011), with a combination of irregular and hyperechoic perinodal fat (De Swarte and others 2011), with an altered vascularisation pattern (Nyman and others 2005, Salwei and others 2005) and with high values of pulsatility and resistivity index (Nyman and others 2005, Prieto and others 2009).

Lymph nodal cyst-like lesions are occasionally identified during ultrasonographic examinations of both human and veterinary patients. In human medicine, they are usually referred to as cystic even in the absence of a ‘true’ cystic lesion, and various cystic echo patterns have been identified in relationship to the histological diagnosis (Ying and others 2013). Liquefaction necrosis has been described as an anechoic area with distal acoustic enhancement, while coagulation necrosis tends to be more echogenic without any clear associated artefact (Ying and others 2013). Regardless of nodal size, lymph nodes with intranodal necrosis are considered pathological (Ying and others 2013). They are commonly found in the neck region in metastatic nodes associated with thyroid carcinoma (Miseikyte-Kaubriene and others 2008, Landry and others 2011, Ying and others 2013), squamous cell carcinoma, as well as in lymph node tuberculosis (Ahuja and others 2008, Ying and others 2013). Concerning abdominal lymph nodes, a specific cavitation syndrome of mesenteric lymph nodes in coeliac patients and omental cysts derived from ectopic lymph nodal tissue have been described (Kumar and others 2009, Freeman 2010, Keer and others 2010, McBride and others 2010). In veterinary medicine, literature is controversial. Cystic lymph nodes can result from the atrophy of the lymphoid tissue (D'Anjou and Carmel 2015) or be considered as malignant lesions, commonly seen in metastases of squamous cell carcinoma (Nyman 2009). Cystic sublumbar lymph node metastases in a dog with anal sac adenocarcinoma have also been reported (Hoelzler and others 2001). In a previous veterinary study, internal anechoic areas were described in 4/61 medial iliac lymph nodes of healthy and diseased dogs, but information about distal acoustic enhancement or histological results was not available (Llabrés-Díaz 2004). Another study focused on the association between lymph nodal heterogeneity and malignancy, but lymph nodes referred to as ‘cavitated’, ‘cystic’, ‘heterogeneous’ and ‘nodular’ were included without differentiating the variable echo pattern of heterogeneity (Kinns and Mai 2007). According to the authors’ experience, lymph nodal anechoic areas associated with distal enhancement are occasionally found during ultrasonographic examination of their patients, even in the absence of other visible lymph nodal abnormalities. Nevertheless, to the authors’ knowledge, very little has been published and a study evaluating their prevalence or clinical significance is lacking.

The aim of this study was to evaluate prevalence, most common location and association with concurrent diseases of cyst-like lymph nodes in dogs detected during ultrasound (US) examination. The authors hypothesised that they had a low prevalence and were not associated with a specific location or concurrent disease.

Materials and methods

Prevalence and localisation study

Owner dogs subjected to complete abdominal ultrasonographic examination in the Diagnostic Imaging Department of the Veterinary Teaching Hospital for clinical reasons over a period of one year (November 2013–October 2014) were included in the study. A complete abdominal ultrasonographic examination was referred to as an abdominal US during which the abdominal organs, the iliosacral and the cranial mesenteric lymphocenters were routinely evaluated. The other lymphocenters were always searched for, and in the presence of US abnormalities affecting a specific organ, the examination was considered complete if the regional lymph nodes were carefully evaluated (eg, the hepatic lymph nodes in the presence of a hepatic disease). Each US examination was supervised by a board-certified radiologist. Two US machines (Aloka Prosound SSD-Alpha10, Aloka, Tokyo, Japan, equipped with a linear and a microconvex 5–10 MHz probe and Esaote MyLab Class C-MyLab, Esaote, Maastricht, the Netherlands, equipped with a microconvex 5–10 and a 6–18 MHz linear transducer, respectively) were used, sometimes with the spatial compound imaging technique. For dogs that underwent more than one abdominal US during this time period, only the first study corresponding to the time of initial diagnosis was included. Lymph nodal lesions were referred to as cyst-like if an anechoic area with distal enhancement was visualised within its parenchyma (Fig 1). Hypoechoic or heterogenous nodular lymph nodes without distal enhancement were excluded. Totally hypoechoic lymph nodes with acoustic enhancement were excluded.

FIG 1:

Ultrasonographic image of a pancreaticoduodenal lymph node, showing an intranodal anechoic area associated with distal acoustic enhancement. This dog was affected by gastric leiomyoma. Histological result of the lymph node was intranodal haemorrhage

The cyst-like lymph nodes were anatomically classified according to their location using an anatomic textbook as a reference (Bezuidenhout 2013) (Table 1). Following identification of cyst-like lymph nodes, the medical records of all patients included in the study were reviewed. Age, gender, breed and bodyweight were retained.

TABLE 1:

Classification of lymphocenters and corresponding lymph nodes, according to their anatomic location, used in this study (Bezuidenhout 2013)

Concurrent disease study

Each dog with a cyst-like lymph nodal lesion was classified in a neoplastic or a non-neoplastic diseases’ group according to its medical record and follow-up. The neoplastic diseases’ group included all dogs with a confirmed cytological or histological diagnosis of neoplasia. When performed, cytological/histological diagnosis was made by board-certified pathologists or by board-certified internists with experience in cytology. Because of the lack of histological or cytological diagnosis of concurrent diseases in some dogs included in the non-neoplastic diseases’ group, results of follow-up examinations were recorded to support the diagnosis. When follow-up clinical examinations were not performed, information was obtained by contacting the owners. Dogs included in the non-neoplastic diseases’ group were further classified into six subtypes: gastroenteropathy, pancreatitis, renal insufficiency, septic peritonitis, benign prostatic disease and neurological disease. Diagnosis of gastroenteropathy was based on a combination of clinical signs (vomiting, diarrhoea, haematemesis, melena), blood work (hypoalbuminaemia, hyperglobulinaemia, increased uraemia), US examination, faecal samples, cytological or histological diagnosis, and on follow-up examinations. Diagnosis of pancreatitis was based on a combination of clinical signs (abdominal pain, vomiting, anorexia), US findings (hyperechoic mesenteric fat in the pancreatic region, hypoechoic, bumpy pancreatic parenchyma) and on canine pancreatic lipase immunoreactivity. Diagnosis of renal insufficiency was based on a combination of clinical signs, the presence of azotaemia (simultaneous increase in creatinine and blood urea nitrogen) and decreased urine-specific gravity. Diagnosis of benign prostatic disease was based on a combination of clinical findings (haematuria, dysuria, stranguria, tenesmus), blood work, prostatic lavage fluid analysis and US examination compatible with benign prostatic hyperplasia and/or prostatic cysts or abscesses. Diagnosis of septic peritonitis was based on a combination of abdominal US (hyperechoic mesenteric fat and echoic abdominal effusion), as well as on cytological analysis, with or without biochemical analysis of free peritoneal fluid.

The neurological disease subtype included dogs affected by primary neurological disease (e g, epilepsy) according to their clinical signs, neurological examination and complementary examinations (cerebrospinal fluid analysis, CT examination of the brain).

χ2 tests were performed to calculate statistical correlation between the presence of a cyst-like lymph nodal lesion and neoplastic or non-neoplastic diseases, and between the presence of this lesion and a specific non-neoplastic disease. A probability value (P<0.05 per cent) was considered statistically significant. All concurrent diseases were considered for statistical study, regardless of the affected region being anatomically drained by the affected lymph node or not. If a dog was concurrently affected by a non-neoplastic and a neoplastic disease, it was included in both groups. Moreover, if a dog was affected by several neoplastic or non-neoplastic concurrent diseases, each of them was counted as a separate disease.

When possible, postmortem or surgically collected cyst-like lymph nodes identified during the US examination were collected for histological analysis. The issue samples were fixed in 10 per cent formalin solution, imbedded in paraffin block and sectioned in 5 µm. They were then coloured with H&E, periodic acid-schiff (PAS) and trichrome. All histopathological examinations of cyst-like lymph nodes were performed by the same board-certified pathologist (MH).

Results

Prevalence and localisation

A total of 553 dogs were included in the study. Twenty-three cyst-like lymph nodal lesions were observed in 17/553 dogs (prevalence of 3 per cent. 95 per cent CI ±0.014; sd 0.007).

Thirteen dogs had only one affected lymph node while four dogs had more than one (three and one dog with two and four affected lymph nodes, respectively). The breeds represented were Jack Russell terriers (two dogs), labrador retrievers (two dogs), an American Staffordshire, a basset hound, a Bernese Mountain dog, a beagle, a Bichon, a Border collie, a boxer, a Brittany spaniel, a French bulldog, a fox terrier, a golden retriever, a poodle and a Tibetan terrier. The age of the dogs ranged from 1 to 13 years with a mean age of 8.4 years. There were five males, two neutered males, six females and four spayed females. Also, 7 out of 23 affected lymph nodes were anatomically classified as lumbar lymphocenter (aortic lymph nodes), 6/23 lymph nodes as coeliac lymphocenter (splenic (2), hepatic (2), gastric (1) and pancreaticoduodenal (1) lymph nodes), 5/23 as iliosacral lymphocenter (medial iliac lymph nodes) and 5/23 as cranial mesenteric lymphocenter (jejunal lymph nodes) (Table 2).

TABLE 2:

Number (n) and anatomic location of cyst-like lymph nodes in a group of 17 dogs

Study on concurrent diseases

A total of 23 concurrent diseases were diagnosed in 17 dogs, 13 dogs with a single disease, 2 dogs with two coexisting diseases and 2 dogs with three coexisting diseases. Also, 16 diseases out 23 (70 per cent) were classified as non-neoplastic and the remaining 7/23 (30 per cent) were classified as neoplastic (Tables 3 and 4).

TABLE 3:

Number of concurrent diseases diagnosed in a group of 17 dogs with cyst-like lymph nodes

TABLE 4:

Number of dogs affected by neoplastic or non-neoplastic disease and corresponding affected lymphocenter

The most common concurrent disease was renal insufficiency, diagnosed in 8/23 diseases. Aortic lymph nodes were affected in four of those dogs (Table 4). One patient had a cystic medial iliac lymph node, one had a cystic hepatic lymph node and one had a cystic jejunal lymph node (Table 4). At the time of writing this article, 2/8 dogs affected by renal insufficiency were still alive (3 and 10 months after the diagnosis), 4/8 dogs died and 2/8 dogs were lost to follow-up (Table 5).

TABLE 5:

Summary of dogs affected by a neoplastic or non-neoplastic disease and corresponding follow-up information

The second most common concurrent disease was neoplasia, which was diagnosed in 7/23 diseases (Table 3). Neoplastic diseases included gastric leiomyoma (one), prostatic sarcoma (one), hepatocellular adenoma ( one) and adrenal gland adenoma (one), stifle histiocytic sarcoma (one), urinary bladder carcinoma (one) and hepatocellular adenocarcinoma (one). One dog was affected by two different primary neoplasms (hepatocellular adenoma and adrenal gland adenoma). Another dog was diagnosed with urinary bladder carcinoma and hepatocellular adenocarcinoma. Final diagnosis was acquired by fine needle aspiration in 3/7 neoplastic cases (prostatic sarcoma, intra-articular histiocytic sarcoma of the stifle and hepatocellular adenocarcinoma) and by US-guided urinary bladder brushing in another neoplastic case (urinary bladder carcinoma) and by histological examinations in 3/7 cases (hepatocellular adenoma, adrenal gland adenoma and gastric leiomyoma). Cytological diagnosis of prostatic sarcoma, urinary bladder and hepatocellular adenocarcinoma was made by a board-certified internist; the remaining cytological diagnosis of histiocytic sarcoma and histological diagnosis of adrenal gland adenoma, hepatocellular adenoma and gastric leiomyoma was made by a board-certified pathologist. The most common affected lymph node in dogs with neoplasia was the medial iliac lymph node, which was identified in 3/5 dogs (gastric leiomyoma, prostatic sarcoma and histiocytic sarcoma).

Pancreaticoduodenal (one) and aortic lymph nodes (two) were affected in one dog affected by gastric leiomyoma, as well as in one dog suffering from both hepatocellular and adrenal gland adenoma. At the time of writing this article, the dog diagnosed with gastric leiomyoma was still alive (24 months after diagnosis); the remaining dogs have been euthanased (Table 5).

In total, 3 out of the 17 dogs were affected by gastroenteropathies (Table 3) and showed cyst-like cranial mesenteric lymph nodes (Table 4). One of those dogs was clinically diagnosed with non-specific gastroenterocolitis, one with lymphangiectasia and one was histologically diagnosed with lymphoplasmacytic enteritis. At the time of writing this article, the dog diagnosed with lymphangiectasia died, while the remaining two dogs were still alive (12 months after diagnosis) (Table 5).

Benign prostatic disease was diagnosed in 2/17 dogs (Table 3), both with iliosacral cyst-like lymph nodes (Table 4). Only one out of the two dogs is still alive (24 months after diagnosis), the other was euthanased because of concurrent neoplastic disease (Table 5).

Pancreatitis, septic peritonitis and neurological disease were diagnosed in three different dogs (Table 3). The coeliac lymph node was affected in the dogs with pancreatitis and septic peritonitis, while the cranial mesenteric lymph node was affected in the remaining dog, diagnosed with idiopathic epilepsy (Table 4). At the time of writing this article, the dogs affected by pancreatitis and by neurological disease are still alive (7 and 10 months after diagnosis, respectively). The dog affected by septic peritonitis died immediately after diagnosis (Table 5).

No statistical correlation was found between the presence of a cyst-like lesion and neoplastic or non-neoplastic diseases, and between presence of this lesion and a specific non-neoplastic disease.

A total of three cyst-like lymph nodes (two lomboaortic and one pancreaticoduodenal) were evaluated histologically. The lomboaortic lymph nodes were removed during postmortem examination in a dog simultaneously affected by renal insufficiency, hepatocellular adenoma and adrenal gland adenoma. On histological examination, the architecture of one of the lymph nodes was disrupted by the formation of large, sharply bordered, heterogeneously distributed, cyst-like spaces, which appeared to belong to the sinuses. The cyst-like spaces presented no specific lining and were filled with blood and serous fluid with localised leucocyte aggregates, mostly composed of lymphocytes and macrophages (Fig 2a,b). Within the remaining non-dilated sinuses of this lymph node, erythrocytes, erythrophages and hemosiderophages could be seen (Fig 2c). The lymphoid tissue remained otherwise within normal limits. The other lymph node presented asymmetrical central and peripheral sinusal spaces that were severely dilated by oedema, causing atrophy of the surrounding lymphoid tissue (Fig 3a,b). The fluid was mostly clear with occasional leucocytes and rare erythrocytes. The follicular architecture of the lymph node was preserved despite its atrophy. There was no particular lining against the cyst-like wall (Fig 3c). Histological examination revealed sinusal haemorrhages and ectasia of the aortic lymph nodes.

FIG 2:

Histological image of a lymph node affected by sinusoid ectasia, after H&E staining. Large cyst-like spaces (stars) are present in the lymph node, slightly disrupting its normal architecture (a, H&E, 40x magnification). The spaces are filled with fluid (b, H&E, 100x magnification) containing red blood cells (arrowhead) or with serum and leucocytes (arrow). The margins are sharp and their surfaces are not lined by cells. Within the rest of the lymph node (c, H&E, 400x magnification), the sinuses drain erythrocytes, erythrophages (short red arrows) and hemosiderophages (long black arrows)

FIG 3:

Histological image of a lymph node affected by sinusoid haemorrhage and ectasia, after H&E staining. In this lymph node, the cyst-like spaces are very large, modifying greatly the node architecture (a, H&E, 40x magnification). They are larger in the central sinuses and contain mainly serous fluid with occasional lymphocytic aggregates (arrowhead). The borders are sharp but occasional follicles (arrow) protrude within the lumen (a and b, H&E, 100x magnification). There are no cells lining the cystic spaces (c, H&E, 400x magnification)

The pancreaticoduodenal lymph node was removed surgically in a dog, undergoing surgery for the removal of a gastric leiomyoma. On histological examination, the architecture of this lymph node was disrupted by the dilation of the central sinus by a large sharply bordered central cyst-like space, with a few isolated lymphoid follicles protruding within its lumen. There was no specific lining covering the internal surface. The space was filled with blood with in some areas aggregates of lymphocytes, macrophages and serous fluid, consistent with haemorrhagic cavities.

Discussion

In the present study, abdominal cyst-like lymph nodal lesions have a low prevalence, involve many lymphocenters and are detected in dogs affected by a variety of concurrent diseases. No statistical correlation existed between the presence of a cyst-like lymph nodal lesion and a specific disease. However, the number of lesions evaluated was small and the absence of a statistical correlation should be confirmed on a larger cohort of dogs. Histologically, in the present study, the lymph nodal cyst-like lesions detected by ultrasonography corresponded to sinusoid ectasia or haemorrhagic cavities.

According to the literature, lymph node identification by ultrasonography is variable. The identification of medial iliac lymph nodes in healthy dog ranges from 45 per cent to 100 per cent (Llabrés-Díaz 2004, Mayer and others 2010). In another study, at least one jejunal lymph node was identified in 57/57 dogs, but gas-filled intestinal loops prevented the complete US assessment in three dogs during the first examination (Agthe and others 2009). In the authors’ institution, abdominal lymph node regions (coeliac, cranial mesenteric, lumbar and iliosacral lymphocenters) are usually inspected, and at least iliosacral and cranial mesenteric lymph nodes are consistently visualised during a complete abdominal US. Nevertheless, in this study, it is possible that some lymph nodes have not been visualised, especially if small in size or in the presence of gastrointestinal gas content. However, in cases of abdominal lesions, the regional draining lymphocenter is always investigated (e g, the hepatic lymph nodes in the presence of a hepatic disease). In this study, the lymph nodes were anatomically classified according to their location using an anatomic textbook as a reference (Bezuidenhout 2013). According to this classification, each lymph node belongs to a lymphocenter. However, it is not always possible to distinguish exactly between lymph nodes and it is possible that some lymph nodes were misclassified, especially in the presence of a mass effect in the abdomen. As selection criteria, only lymph nodes with anechoic areas associated with distal acoustic enhancement were included. This artefact should be useful in identifying fluid-filled lesions. However, a lesion with an increased scattering but low absorption can result in the same pattern, suggesting the use of a subjective assessment of the attenuation degree (O'Brien 1998). Moreover, the visualisation of distal enhancement can be reduced when using spatial compound imaging because of averaging of the overlapping scan images (Hangiandreou 2003). However, in a recent veterinary study, no apparent difference of the acoustic enhancement artefact with spatial compound imaging was noticed (Heng and Widmer 2010). It has been postulated that this result could be secondary to the large size of the evaluated structure and that it was reasonable to expect a decreased acoustic enhancement with smaller cyst-like structures (Heng and Widmer 2010). Therefore, it is possible that in this study some cyst-like lymph nodes were misclassified or missed.

In human medicine, cyst lymph nodes are usually considered malignant and associated with papillary thyroid carcinoma metastases, squamous cell carcinoma or tuberculous nodes and they are usually found in the cervical region (Ahuja and others 2008, Miseikyte-Kaubriene and others 2008, Landry and others 2011, Ying and others 2013). However, their US cyst-like appearance is often not histologically a true cyst, but corresponds to intranodal necrosis (Ying and others 2013). Cavitation of mesenteric lymph nodes has also been described (Freeman 2010, Keer and others 2010, McBride and others 2010). It is considered a rare, poorly understood complication in patients affected by coeliac disease, and it is usually indicative of a poor prognosis with a mortality of approximately 50 per cent (Freeman 2010, Keer and others 2010, McBride and others 2010). Although its pathogenesis is unknown, it has been postulated that excessive antigenic exposure of the immune system via a damaged intestinal mucosa leads to depletion of cellular lymphoid elements and finally to a cyst-like lymph nodal appearance (Keer and others 2010, McBride and others 2010). Alternatively, other theories involve necrosis or intravascular coagulation (Freeman 2010, Keer and others 2010, McBride and others 2010). Other differential diagnoses for cyst-like mesenteric lymph nodes in human medicine are lymphoma, mycobacterial infection or omental cysts (Kumar and others 2009, Keer and others 2010). The latter are found in the greater and lesser omentum and are believed to originate from benign proliferations of ectopic lymphatic that lacks communication with the normal lymphatic system (Kumar and others 2009). In this study, no statistical correlation existed between a specific disease and the presence of cyst-like lymph nodes. However, this result should be evaluated taking into account the small number of dogs and histological exams and the absence of a control group. Indeed, all these limitations prevent the authors from drawing statistical conclusions concerning the association between the presence of a cyst-like lesion and a specific neoplastic or non-neoplastic disease. Rather, according to the authors, the results of this study highlight that the presence of a lymph nodal ‘cyst-like’ lesion should not be always interpreted as a malignant lesion. In this study, coexisting diseases were classified according to clinical or cytological diagnosis and it is possible that some diagnoses were wrong or misclassified. Histology and cytology were not always available because of the deep position of the lymph node and/or of the lesion or because of the owner's decision. However, to compensate the latter limitation, follow-up information was recorded and the authors can postulate that in a certain amount of cases follow-up information supported the diagnosis of non-neoplastic disease. Histological results, although performed on a limited number of patients, showed sinusoid ectasia and intranodal haemorrhage. Therefore, given the absence of histologically confirmed cystic lesions, the authors preferred to describe these lesions as ‘cyst-like’, instead of ‘cystic’. To the authors’ knowledge, very little is published concerning sinusoid ectasia and intranodal haemorrhage. Lymphatic sinus ectasia has been described in the mesenteric lymph nodes of mice as dilated or cystic sinuses (Elmore 2006), likely secondary to obstruction of efferent lymph vessels (McInnes 2012). The small number of histological examinations allows the authors only to postulate that different mechanisms than necrosis may lead to intranodal cavitary lesions in dogs compared with human beings. Further histological studies are needed to clarify this aspect.

In conclusion, the results of this study suggest that abdominal cyst-like lymph nodal lesions have a low prevalence in dogs and that they can be detected in dogs affected by a variety of diseases, including both non-neoplastic and neoplastic aetiologies. However, their possible association with a specific disease should be further evaluated on a larger cohort of dogs. Histologically no intranodal necrosis has been diagnosed, but instead their cyst-like appearance can be secondary to sinusoid haemorrhage and sinusoid ectasia.

Acknowledgments

The authors acknowledge Dr Sarah Porter for her writing assistance.

  • Accepted December 11, 2016.

References

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Footnotes

  • Previous presentations: Presented as an oral communication at the 2015 Annual International SCIVAC meeting, May 29–31, 2015, Rimini, Italy.

  • Provenance: Not commissioned; externally peer reviewed

  • Provenance: Not commissioned; externally peer reviewed

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