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Dogs
A case of isolated diffuse splenic haemangiomatosis in a dog
  1. Daniela Murgia1,
  2. Moira Mori2,
  3. Marco Rondena3 and
  4. Damiana Tacchini4
  1. 1Department of Surgery, Animal Health Trust, Newmarket, Suffolk, UK
  2. 2Free Lance, Siena, Italy
  3. 3Clinica Veterinaria San Marco, Padova, Italy
  4. 4Department of Pathology, Policlinico S. Maria alle Scotte, Siena, Italy
  1. Correspondence to Dr Daniela Murgia, danielamurgia.dm{at}gmail.com

Abstract

This report describes a case of isolated diffuse haemangiomatosis in the spleen of a nine-month-old dog that presented with weakness, abdominal discomfort and severe splenomegaly. Histopathological examination following splenectomy showed the splenic parenchyma had almost been replaced by multiple dilated vascular lacunae, varying is size, and lined by a single layer of flattened, well differentiated, endothelial cells sustained by fine fibrocystic bundles. The cytoplasmic expression of CD34 and von Willebrand factor found in the endothelial cells confirmed the vascular nature of the lesion; the lack of expression of podoplanin, a specific marker for the lymphatic vessels, excluded the diagnosis of lymphangiomatosis. Diffuse splenic haemangiomatosis carries a benign prognosis and complete cure following splenectomy has been described in humans and was achieved in this case. However, the differential diagnosis must take into account the possibility of vascular malignant or tumour-like lesions occurring in the spleen.

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Background

In humans the most common primary splenic connective tissue tumours are vascular in origin (Arber and others 1997). The main differential diagnoses include lymphangiomas, haemangiomas, haemangioendotheliomas, angiosarcomas, littoral cell angiomas and hamartomas (also called splenomas) (Dufau and others 1999). While tumours of the spleen seem to be rare in humans, in dogs up to two-thirds of splenic malignancies are angiogenic in origin and are represented by haemangiosarcomas (Christiansen and others 2009). Among the malignant tumour sarcomas, fibrohistiocytic nodules as well as lymphoma and mast cell tumours have also been described in dogs. In this species, splenic benign lesions include haemangioma, haematoma, nodular hyperplasia and splenitis (Eberle and others 2012).

Angiomatosis is a vascular endothelial proliferative disorder causing hyperplasia and dysplasia of blood (haemangiomatosis) and lymphatic vessels (lymphangiomatosis) (Dufau and others 1999). Diffuse splenic haemangiomatosis may occur as a manifestation of systemic angiomatosis; less commonly, it is confined to the spleen and is usually classified as a benign disorder. In humans it is sometimes accompanied by severe disturbance of blood coagulation and extramedullary haemopoiesis. This condition is also known as Kasabach-Merrit syndrome (Dufau and others 1999).

Isolated diffuse haemangiomatosis of the spleen is a very rare lesion and only 14 cases have been reported in humans (Dufau and others 1999). To the authors’ knowledge there have been no previously published reports of isolated diffuse splenic haemangiomatosis in the dog.

Case presentation

A nine-month-old, entire, 14 kg, male crossbreed dog was presented with a history of recurrent episodes of weakness, abdominal pain and poor appetite alternating with periods of wellness.

Upon presentation the dog was subdued. Physical examination revealed no abnormalities, apart from mildly pale mucous membranes and splenomegaly on abdominal palpation. Full blood analysis revealed red blood cell count (RBC) 6.07×1012/l (5.5 to 8.5×1012/l), packed cell volume 49.2 per cent (37.0 to 55.0 per cent), haemoglobin 159 g/l (120 to 180 g/l), mean corpuscular volume 81 fL (60.0 to 77.0 fL), platelet count 371 K/µl (175 to 500 K/µl), mild leucocytosis with white blood cell count 22.81 K/µl (5.50 to 16.90 K/µl), neutrophilia 14.41 K/µl (2.00 to 12.00 K/µl) and lymphocytosis 6.73 K/µl (0.50–4.90 K/µl). Biochemistry, coagulation profile and urine analysis revealed no abnormalities.

Investigations and treatment

Thoracic radiographs were unremarkable. Abdominal ultrasonography showed evident splenomegaly with diffuse dishomogeneous echostructure. The splenic parenchyma presented as multiple, diffuse, hypo- and anechoic cystic lesions varying in size from a few millimetres to a few centimetres (Fig 1). No abnormalities of the other abdominal organs were detected. The cystic fluid appeared clear in colour and biochemistry was unremarkable. Protein content and cellularity were low. Cytological examination showed pleomorphic macrophages with cytoplasmic vacuolisations and erythrophagocytic activity secondary to mild aspecific macrophagic inflammation.

FIG 1:

Abdominal ultrasonography showing severe splenomegaly associated with diffuse dishomogeneous echostructure. The splenic parenchyma presented multiple hypo- and anechoic cystic lesions (white asterisks) of different dimensions (from a few millimetres to a few centimetres)

Within a few days of first presenting, the dog's condition and demeanour deteriorated, with signs of anorexia, discomfort and an unwillingness to move.

Clinical assessment showed pale mucosal membranes, capillary refill time >3 seconds, mild tachycardia, respiratory rate within normal ranges, and a temperature of 38°C. Transabdominal palpation and repeat abdominal ultrasonography revealed pain and a further increase of splenic dimensions. Repeat blood work up, including haematology, comprehensive biochemistry and coagulation profile, was unremarkable, as was echocardiography and electrocardiography. Total body CT scan was also unremarkable. Following preliminary cardiovascular stabilisation, an exploratory laparotomy and splenectomy were performed. Upon abdominal exploration, no haemoperitoneum was present. The spleen appeared hugely swollen (30 cm in length, 15 cm wide and 8 cm thick) and diffusely lobulated, and weighed 1230 g (Fig 2). On cut surface, the splenic parenchyma was completely replaced by several white-greyish cystic lesions of various sizes. All the other abdominal organs were grossly normal.

FIG 2:

(a and b) Diffuse splenic haemangiomatosis. Macroscopic appearance of the spleen following splenectomy. Evident generalised enlargement of the organ presenting multiple diffuse nodular and lacunar lesions bulging from the organ capsule

Representative samples of the lesion were chosen, fixed in 10 per cent buffered formalin for 12 hours, embedded in paraffin, routinely processed, cut in 4 µm-thick sections and stained with haematoxylin and eosin. Selected slides were used for immunohistochemical staining, using the labelled streptavidin–biotin complex method. The primary mouse monoclonal antibodies against CD8, CD34, smooth muscle actin, podoplanin, von Willebrand factor (vWF) and Ki67 were used. Histologic examination showed multiple thin walled cysts, filled by pink, amorphous material (plasma) or RBC in the absence of clear connections or anastomosis between them. A single layer of flattened or spindle-shaped endothelial cells with round, centrally located nuclei, low nuclear/cytoplasmic ratio (N/C) and abundant, slightly basophilic cytoplasm lined the wall of the cysts.

Nuclear chromatin was clumped and nucleoli were absent. A little anisocytosis was visible but atypical mitoses were absent. Occasionally, partly organised parietal thrombi were visible inside the cysts (Fig 3). In those areas of the spleen where there was less involvement of the vascular lacunae, scattered foci of residual spleen parenchyma were visible. Here, the red pulp was expanded by elevated numbers of erythroid, myeloid and megakaryocytic haematopoietic cells admixed with plasma cells and macrophages, suggesting extramedullary haematopoiesis. In addition, highly dilated splenic sinuses were visible. The white pulp was characterised by mild follicular hyperplasia.

FIG 3:

(a) Diffuse splenic haemangiomatosis. Representative section of splenic parenchyma showing several, variably sized lacunae, broadly affecting the red pulp. The lesions are not encapsulated and not demarcated (haematoxylin and eosin, ×50). (b) Diffuse splenic haemangiomatosis. Representative section of splenic vascular proliferation with thin walled, non-anatomised cysts, filled with amorphous material or red blood cells (H&E, ×100). (c) Diffuse splenic haemangiomatosis. Representative section of splenic parenchyma at higher magnification. A single layer of flattened endothelial cells cover the cystic wall. Endothelial cells are not atypical and they show basophilic cytoplasm and round nuclei (H&E, ×200)

In order to determine the possible vascular nature of the lesions and to differentiate haemangiomatosis from lymphangiomatosis, immunohistochemical investigation using α smooth muscle actin (ASMA-clone ASM-1, prediluted, Novocastra, Florence, Italy), CD34 (Clone QBEND/10, 1:50, Novocastra), podoplanin (clone D2-40, prediluted, Dako Cytomatic, Milan, Italy) and human vWF (clone 36B11, prediluted, Novocastra) antibodies was performed. The endothelial cells were supported by one or two layers of smooth muscle cells, as demonstrated by immunohistochemical positivity for ASMA antibody, which detected a continuous layer of smooth muscle cells in the vascular walls. The positivity of endothelial cells lining the cysts for CD34 and vWF confirmed the haemangiomatous nature of the process. In addition negativity for podoplanin, a specific marker for the endothelium of the lymphatic vessels, excluded the diagnosis of lymphangiomatosis (fig 4).

FIG 4:

(a) Diffuse splenic haemangiomatosis. Immunohistochemical staining for CD34 shows a strong positive reaction in normal sinusoidal endothelial cells of the red pulp and in the endothelial cells of the cysts (haematoxylin and eosin, ×100). (b) Diffuse splenic haemangiomatosis. Negative immunostaining for podoplanin in endothelial lining cells of cystic walls (right); positive reaction is appreciable in endothelial lymphatic vessels of the adjacent spleen parenchyma (left) (H&E, ×100)

CD8 positivity was consistently detectable in splenic sinuses while cyst endothelium was negative. The proliferative index observed in endothelial cells was extremely low (<1 per cent/10 high powered fields).

Outcome and follow-up

According to the clinical presentation and histological findings, a diagnosis of isolated diffuse benign splenic haemangiomatosis was established.

The splenectomy and postoperative recovery were straightforward, and at 400 days post-surgery, the dog is clinically well.

Discussion

Splenomegaly is a common clinical finding in dogs. Reports suggest that benign disorders of growth, vascular disturbances and necrosis are the most commonly diagnosed canine splenic disorders, followed by malignant neoplasms, equivocal diagnosis and inflammatory processes (Cortese and others 1988, Levey and others 1996, Dufau and others 1999). Splenic canine neoplasms are classified into three main groups. Haematopoietic neoplasia such as lymphoma, large granular, lymphocytic and lymphoblastic leukaemia, mast cell, and plasma cell tumours represent 5–24 per cent of splenic lesions (Warzee 2012). Non-haematopoietic neoplastic forms include benign and malignant lesions, and haemangiosarcoma is the most common malignancy reported (Cortese and others 1988, Levey and others 1996, Smith 2003). A variety of non-angiogenic and non-lymphomatous sarcomas can also affect the canine spleen. Among these, the most frequently reported are histiocytic sarcoma, leiomyosarcoma, fibrosarcoma, undifferentiated sarcoma, metastatic sarcoma and neuroendocrine neoplasia (Warzee 2012). Haemangioma, haematoma, leiomyoma, fibroma, lipoma, benign nodular lymphoid hyperplasia and haematopoietic nodules represent the benign counterpart that affect the canine spleen.

This case report describes the histological diagnosis and surgical treatment of isolated diffuse splenic haemangiomatosis in a dog. Clinical forms of angiomatosis have previously been recognised in dogs. These include cutaneous angiomatosis (Peavy and others 2001, Kim and others 2005, Olivieri and others 2010), scrotal-type vascular hamartoma or progressive angiomatosis, in which the lesions were mainly on the scrotal area and acral areas or face, respectively (Gross and others 2005, Olivieri and others 2010), skeletal–extraskeletal angiomatosis (Kuroki and others 2010), and multisystem progressive angiomatosis where the lesions were mainly cutaneous, oesophageal or gastrointestinal, or on the visceral peritoneal lining of abdominal organs (Ide and others 2013). Gal and others (2013) reported a case of splenic littoral cell angiosarcoma in a beagle. Littoral cells are splenic red pulp sinusoidal lining cells with immunohistochemical characteristics intermediate between endothelium and histiocytes. Cutaneous angiomatosis has also been described in cats (Affolter and others 2004). Similar lesions have been reported in humans. For example, three cases of splenic angiomatosis, one single case of cystic angiomatosis (CA) with splenic involvement, and 14 cases of isolated diffuse haemangiomatosis of the spleen have been described (Cortese and others 1988, Shiran and others 1990, Dufau and others 1999, Vanhoenacker and others 2003), whereas no case of diffuse haemangiomatosis confined to the spleen has been previously reported in dogs. In human medicine, patients with angiomatosis are mainly affected within the first decades of life (Levey and others 1996). Roughly 30–40 per cent of angiomatosis cases present diffuse osseous infiltration and follow an indolent course, while 60–70 per cent are characterised by soft tissue and visceral involvement, which has a much poorer prognosis (Murphey and others 1995). One variant of angiomatosis is CA, which can be defined as widespread involvement of both the vascular and lymphatic systems, producing diffuse skeletal cystic lesions with or without visceral involvement (Levey and others 1996). Isolated diffuse splenic haemangiomatosis is a rare benign vascular condition and in humans is sometimes accompanied by severe disturbance of blood coagulation (Dufau and others 1999). Signs and symptoms include anaemia, thrombocytopenia, disseminated intravascular coagulopathy and splenomegaly (Dufau and others 1999). Only splenomegaly has been described in the case reported here. However, similar to the sonographic appearance of splenic haemangiomatosis in humans, the spleen of the dog in this report presented multiseptated lobules with anechoic content and minimal detectable residual splenic parenchyma.

Furthermore, the microscopic examination of the haemangiomatous splenic parenchyma resembled the histological findings reported in the human literature. In fact, the haemangiomatous lesions involved the entire spleen diffusely and were distributed randomly through the red pulp, with only scattered areas of residual tissue. The pathological vessels were mostly thin-walled, cavernous, and lined by flat endothelial cells (Dufau and others 1999).

The differential diagnosis of diffuse haemangiomatosis must take into account the other most frequently diagnosed canine splenic vascular tumours such as haemangiosarcoma, haemangioendothelioma, haemangioma, lymphangiomatosis, nodular lymphoid hyperplasia or tumour-like lesions occurring in the spleen, such as splenic haematoma or hamartoma.

Haemangiosarcoma, unlike in the case here reported, presents either as a single mass with haemorrhagic texture or as multiple nodules within the spleen or, less frequently, as a diffuse cavernous lesion that does not involve the entire splenic parenchyma. Microscopically, the growth pattern of haemangiosarcoma can be solid, papillary or epithelioid. Unlike haemangiomatosis, haemangiosarcoma has multiple anastomosing vascular lacunae and endothelial cells showing marked pleomorphism, severe atypia and mitoses. The proliferative index is high and the course is invariably fatal, with early haematogenous metastasis. Oncological staging of patients has failed to show metastatic spread of the disease to other organs.

In the same manner, haemangioendothelioma can be ruled out in the differential diagnosis as cytologic atypia or mitoses and ki67 were absent.

From a clinical and histological point of view, in our case the main differential diagnosis was represented by splenic haemangioma. Canine splenic haemangioma is rarely reported in dogs, and usually presents as a non-encapsulated, well-demarcated, locally extensive, non-infiltrative and expansive mass. In the majority of cases haemangiomas are solitary tumours with partial involvement of the organ or tissue and without any relevant clinical signs (Walsh and Schneck 1974, Day and others 1995, Gamlem and others 2008). Occasionally haemangiomas may present with separated multiple nodules, with the characteristics discussed above.

Haemangioma is histologically similar to haemangiomatosis, comprising a proliferation of vascular channels ranging from capillary to cavernous, lined with endothelium without atypia. In the present case the lesion was not circumscribed and extended diffusely through the splenic parenchyma, with innumerable variably sized lacunae, grossly bulging from the splenic capsule. On the basis of these findings the diagnosis of haemangiomatosis was made.

Lymphangioma (and the diffuse variant of lymphangiomatosis) is characterised by proliferation of lymphatic channels in the spleen that can lead to splenomegaly. Unlike in our case, the lining endothelial cells are almost negative for CD34 or other vascular markers (Rose and others 1986), and should be positive for lymphatic markers, such as D2-40 (Kahn and others 2002).

Nodular splenomegaly in animals can also be secondary to non-neoplastic proliferation of cells normally found in the spleen, such as lymphoid cells (nodular lymphoid hyperplasia and haematopoietic nodules).

In benign nodular lymphoid hyperplasia lesions the expansion of the marginal zone or, less frequently, of the germinal centre of lymphoid follicles leads to compression of the high endothelial follicular associated artery, causing vessel dilation and locally extensive congestion resulting in haematomas. Similarly, large haematopoietic nodules may cause alterations in local blood flow, with formation of haematomas (Fry and McGavin 2012, Mosier 2012). In the present case, a further differential was considered, related to a vascular dilation secondary to splenic nodular hyperplasia. However, in the splenic white pulp, neither marginal zone nor germinal centre expansion of the lymphoid follicles was evident, thus a locally extensive congestion secondary to nodular lymphoid hyperplasia was excluded. Moreover histologically, benign hyperplastic nodular lymphoid lesions lack of cystic spaces and tumoral mass consists of a solid proliferation of multiple lymphoid follicles in the white pulp, with mitotically active germinal centres and a well-defined lymphocytes mantle. The absence of lymphoid reactive follicles in our case excluded the diagnosis of nodular lymphoid hyperplasia.

Splenic haematoma is a collection of blood in the splenic parenchyma that occurs more frequently after blunt abdominal trauma. Haematoma is usually asymptomatic or can give rise to non-specific abdominal pain. Mild anaemia can be the only non-specific, altered blood parameter. Histologically, there is an accumulation of erythrocytes in the splenic pulp, not delineated by the epithelial lining. In our case, clinical symptoms and histological evaluation exclude the diagnosis of haematoma.

Splenic hamartoma is an abnormal amount of normal red pulp that develops as a circumscribed mass in the spleen parenchyma. Histologically, it consists of small to medium sized, irregularly arranged spaces covered by splenic sinus endothelium. However, unlike in our case, splenic sinus lining cells of hamartoma are positive for CD8 and factor VIII-related antigen.

Splenectomy usually results in complete cure of isolated splenic haemangiomatosis in humans, and this was also achieved in the reported case. However, because of limited reports in the literature, the classification, pathogenesis, biological behaviour and outcome of splenic diffuse haemangiomatosis in dogs are still not well established.

In addition, in humans the pathogenesis of haemangiomatosis is debateable. Many pathologists accept a neoplastic origin and diffuse haemangiomatosis may be classified as a benign proliferation of endothelial cells. However, it is currently believed that this lesion results from a vascular malformation of congenital origin rather than a neoplasm. Angiomatous areas could be secondary to intrasplenic distortions and dilation of the post-sinusal venous system, resulting in a characteristic cavernous pattern (Dufau and others 1999).

In conclusion, diffuse splenic haemangiomatosis is a rare primary splenic vascular disease characterised by dispersion through the red pulp of pathological vessels mostly with cavernous morphology. The issue of whether it is neoplastic or malformative in origin is still questionable, and although there is a marked preference for the latter, no definitive proof in favour of either hypothesis has been reported. In the absence of other reported cases in veterinary medicine, and based on human medicine literature, the authors believe that diagnosed diffuse splenic haemangiomatosis carries a benign prognosis. However, the differential diagnosis must take into account the other vascular malignant lesions or tumour-like processes that can occur in the spleen.

Acknowledgments

We would like to thank Dr Sergio Fanfoni for the ultrasound images of the spleen.

  • Received November 23, 2014.
  • Revision received February 7, 2015.
  • Accepted February 28, 2015.

References

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Footnotes

  • Contributors I certify that neither this manuscript nor one with substantially similar content under my authorship has been published or is being considered for publication elsewhere.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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