EQUINE VETERINARY EDUCATION Equine vet. Educ. (2017) () - doi: 10.1111/eve.12766
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Case Report
Malignant peripheral nerve sheath tumour with metastasis and expression of endothelial differentiation factors in a horse res†, A. C. L. Ca ^ mara†* C. S. Boue and A. R. Teixeira Neto†
, M. B. Castro†, E. F. Barbosa†, C. A. Souza‡, R. Serakides‡
†
Large Animal Veterinary Teaching Hospital, Faculty of Agronomy and Veterinary Medicine, University of Brasılia, Granja do Torto, Brasılia, ‡Pathology Laboratory, Veterinary School, Federal Rural University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. *Corresponding author email:
[email protected] Keywords: horse; immunohistochemistry; metastasis; neurofibrosarcoma
Summary
Clinical and laboratory findings
Malignant peripheral nerve sheath tumour (MPNST) has not previously been well documented in veterinary literature. This article reports the case of a 12-year-old Mangalarga Marchador gelding presented for evaluation of a large, ulcerated and pruritic lesion in the elbow of the left forelimb. Biopsy of the mass indicated an undifferentiated sarcoma. Considering the chronicity of the condition, poor prognosis and extensive nature of the neoplasm, the horse was subjected to euthanasia. A MPNST with expression of endothelial differentiation factors was diagnosed based on gross morphology results, histological features and immunohistochemical findings.
Physical examination revealed apathy, mild dehydration, poor corporal body score, tachycardia (48 beats/min), tachypnoea (28 breaths/min) and fever (39.8°C). A firm and ulcerated mass measuring approximately 50 9 20 cm was present in the elbow (olecranon region) of the left forelimb (Fig 1a). The adjacent areas (from the scapula to the olecranon) were hyperthermic, oedematous and sensitive to palpation. The lesion appeared to be adhered to the underlying musculature, which interfered with the movement of the horse causing grade 3/5 lameness. Myiasis and tissue necrosis were also present. No masses were found elsewhere in the body. Haematology indicated a low haematocrit (27%), leucocytosis (17.7 9 109/L) by neutrophilia (12.9 9 109/L), hyperfibrinogenaemia (8.0 g/L) and vacuolated monocytes. Serum biochemistry profiles (urea, creatinine, albumin, total plasma protein and the activities of the enzymes aspartate aminotransferase and c-glutamyl transferase) were within normal limits. Radiographic examination revealed a soft tissue density over the swelling with no apparent bone changes.
Introduction Malignant peripheral nerve sheath tumours (MPNST) consist of a group of similar, but distinct, neural crest neoplasms which arise from either Schwann or modified Schwann cells, perineurial cells, fibroblasts or a compound of these cell types (Koestner and Higgins 2002). These neoplasms have been infrequently documented in man and there are even fewer reports in domestic animals, especially large animals (Strubbe 2001). In horses, some regions of the body can be affected (Nikolaou et al. 2015); however, malignancy has so far not been well characterized. A conclusive diagnosis is challenging and should be based on clinical evaluation, histopathological and immunohistochemical results. Further utilization of transmission electron microscopy may be used to exclude the most similar spindle cell tumours, as fibrosarcoma and Schwannoma (Saulez et al. 2009). The present report describes the clinical, pathological and immunohistochemical findings related to a metastatic MPNST with expression of endothelial differentiation factors in a horse.
Case history A 12-year-old Mangalarga Marchador gelding weighing 350 kg was seen for evaluation of a large, ulcerated and pruritic lesion in the elbow of the left forelimb. The owner reported that the lesion presented itself initially as a nodule 3 months earlier. At that time, the owner decided to incise the lesion with a switchblade, noting a firm and bloody mass. Since then, the lesion had increased in size and the horse had progressively lost weight.
Pathological and immunohistochemical findings Biopsy of the mass indicated an undifferentiated sarcoma. Considering the chronicity of the condition, poor prognosis and extensive nature of the neoplasm, the horse was subjected to euthanasia. Necropsy revealed a yellowishwhite, moderately circumscribed and firm mass in the left forelimb measuring approximately 50 9 20 cm (Fig 1a), which expanded and infiltrated the subcutaneous tissue and musculature, extending from the proximal region of the radius to the left pectoral muscles. The cutaneous surface presented blackened, irregular and ulcerated aspect. The thoracic cavity also contained nodules of similar tissue, specifically in both sides of the parietal pleura, lymph nodes, pericardium, diaphragm and pulmonary parenchyma (Fig 1b,c). Such nodules were well defined, moderately regular and adhered to the underlying respective organ, ranging from 0.3 to 8.0 cm in diameter. The cut surface was firm and yellowish-white. Grossly, the organs of the abdominal cavity were not involved. Tissue samples of the tumour mass, thoracic cavity nodules, lymph nodes, spleen, lungs, liver, heart, diaphragm, urinary bladder, small and large intestines, kidneys and central nervous system were collected for histological analysis.
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Malignant peripheral nerve sheath tumour with metastasis
a)
b)
Histologically, a densely cellular neoplastic proliferation with highly pleomorphic cells that varied in volume and shape from fusiform to round was observed expanding, dissecting, compressing and replacing the striated musculature. The nuclei had granular to dense chromatin and one to three prominent nucleoli (Fig 2a). Six mitotic figures were observed in 10 fields at 4009 magnification. Visceral and parietal pleura, lymph nodes, pericardium, diaphragm, lungs and pericardium samples showed a very similar pattern of neoplastic proliferation and infiltration, with highly pleomorphic cells varying from fusiform to round. In this sample, the chromatin exhibited a mostly loose feature, containing from one to three prominent nucleoli, with rare binucleated cells. Three mitotic figures were observed in 10 fields at 4009 magnification. Loss of cellular structure, eosinophilic debris and pyknotic cells were observed multifocally, besides moderate to intense vascular proliferation and moderate to coalescent lymphoplasmacytic infiltrate. Pulmonary nodules compressed the underlying parenchyma causing focal atelectasis. Due to the intense pleomorphism and lack of cellular differentiation, it was not possible to characterize the cellular origin of the neoplasm. Immunohistochemistry (IHC) was conducted to establish a final diagnosis of the tumour origin. The following antibodies were applied: anti-vimentin (clone V9, 1:50 dilution), anti-a-smooth muscle actin (clone HHF 35, 1:200), anti-S100 protein (code Z0311, 1:100), antifactor VIII (1:100), anti-skeletal muscle myosin (1:100), anti-VEGF (1:100) and anti-CD31 (1:100). The streptavidinbiotin-peroxidase1 and diaminobenzidine complexes2 were used as the detection system. The sections were counterstained with Harris haematoxylin. The positive control was animal tissue positive for the antibodies used. The negative control was tumoural tissue from the gelding that had been incubated with immunoglobulin G in substitution to primary antibodies. Immunohistochemically, vimentin, S100 protein and vascular endothelial growth factor (VEGF) were strongly and diffusely positive in the cytoplasm of more than 90% of the neoplastic cells. Approximately 80% of the tumour cells presented immunolabeling for factor VIII (Fig 2b–e). There was no expression of skeletal muscle myosin and a-smooth muscle actin. A malignant peripheral nerve sheath tumour (MPNST) with expression of endothelial differentiation factors was diagnosed based on gross morphology, histological features and immunohistochemical results.
Discussion
c) Fig 1: Macroscopic aspect of MPNST in a horse. a) An ulcerated and firm approximately 50 3 20 cm mass in the olecranon region of the left forelimb, b) Thoracic cavity containing several nodules in the parietal pleura, lymph nodes, pericardium, diaphragm and pulmonary parenchyma and c) Several nodules on the diaphragm.
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Peripheral nerve sheath tumours (PNSTs) comprise a group of miscellaneous neoplasms which arise from Schwann or modified Schwann cells, perineural cells, fibroblasts, or a combination of these cell types. Because they are microscopically undifferentiated, the malignant forms of schwannoma and neurofibroma have been aggregated under the definition of MPNST (Koestner and Higgins 2002). Such classification, unlike the one used in human pathology, has still not been generally accepted since some authors have suggested that there are variants of schwannoma and neurofibroma in domestic animals similar to those recognized € niger et al. 2011). In order to meet both criteria, in man (Scho this study opted to refer to the present neoplasia as MPNST or neurofibrosarcoma.
res et al. C. S. Boue
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a)
c)
d)
b)
e)
Fig 2: Histological and immunohistochemical features of MPNST in a horse. a) Densely cellular neoplastic proliferation with highly pleomorphic cells that varied in volume and shape from fusiform to round. Nuclei contained from one to three prominent nucleoli. Mild lymphocytic infiltrate. Haematoxylin-eosin, Bar: 100 lm. Immunoexpression of S100 protein b), factor VIII c), vascular endothelial growth factor (VEGF) d) and vimentin e) in the cytoplasm of the neoplastic cells. Streptavidin-biotin-peroxidase complex, Harris haematoxylin, Bar: 100 lm.
The prevalence of MPNST in man is about 5% of all soft tissue sarcomas (Storm et al. 1980). These types of tumours are well characterized, especially as a consequence of neurofibromatosis. In veterinary species, there are rare reports of such neoplasms affecting dogs (Carmichael and Griffiths 1991; Silva et al. 2007; Bergmann et al. 2009), cats (Watrous et al. 1999; Pavia et al. 2012), cattle (Beytut 2006) and goats (Ramırez et al. 2007). In a survey of equine cutaneous neoplasia, only 1.1% were schwannomas € niger et al. 2011). The prevalence of PNST in horses (Scho appears to be very low, reportedly occurring in the small intestine (Kirchhof et al. 1996), perianal region (Sturgeon et al. 2008), male external genitalia (Van den Top et al. 2008), extradurally in the cranium (Williamson and Farrell 1990), external auditory canal (Ahmadi et al. 2013), skin € niger et al. 2011; Silva et al. 2012), mediastinum (Scho (Andreasen et al. 1993), cornea (Kappe et al. 2009), periorbital region (Strubbe 2001), heart (Quinn et al. 2005) and the epaxial musculature (Nikolaou et al. 2015). Of these reports, only the last four represent cases of MPNST, showing its rare occurrence. In a study of 22 horses, the neoplastic growth had lasted reportedly from a few months to 1–3 years in nine cases, while a recent size increase was € niger et al. 2011), similar to this observed in five horses (Scho case report. The same study stated that progression of the benign forms to MPNST had not been documented in horses, although malignant transformation occurred in some human patients with neurofibromatosis type 1. On the other
hand, Nikolaou et al. (2015) reported an equine MPNST case whose clinical data would suggest an initially benign process. Differential diagnoses should include proliferative granulation tissue, foreign body reaction, bacterial or fungal granuloma, parasitic granuloma (especially habronemiasis) and other neoplasms, such as sarcoid, squamous cell carcinoma, fibroma, fibrosarcoma and rhabdomyosarcoma. Most of these were excluded after physical examination, blood analysis, radiographs and biopsy results. Generally, the organization pattern of most of the cells of MPNST consists of small interwoven bundles interposed by collagen or mucinous stroma. Whorls rather than blood vessels may be observed around collagen bundles. Although cell palisades can be noted (most frequently in the benign forms), a much more highly cellular pattern is found in the MPNSTs. Increased perivascular cellularity (scattered lymphocytes and mast cells), nuclear enlargement and necrosis are other common findings. Nuclei are oval with mild pleomorphism. There is certain variation in the mitotic index; however, more than four mitoses per 10 fields are expected (Koestner and Higgins 2002; Skovronsky and Oberholtzer 2004). Gupta and Maniker (2007) suggested that more than five mitotic figures per 10 fields could indicate a high grade tumour in man, taking into consideration that a single mitotic figure may be significant in a densely cellular, anaplastic tumour. This case shows that the histopathological findings perfectly relate to those described in the literature with added macroscopic
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evidence of local infiltration and pulmonary metastases, in contrast with the information that MPNSTs in man are rarely metastatic (Guo et al. 2012). Presumed tumour metastases to the lungs of domestic animals, positive for S-100 staining, have only been described in dogs and cats until this date (Carmichael and Griffiths 1991). Unfortunately, but as expected, this study was not able to establish a final diagnosis based solely on histopathological analysis. Frequently, in some MPNST, diagnostic morphology cannot be conclusive, as several histological features common to a variety of neoplasms may overlap and be indistinct, making it impossible to differentiate them from other spindle cell tumours and thus establish a secure diagnosis (Koestner and Higgins 2002; Quinn et al. 2005). As IHC has evolved and become more routine, including more specific antibodies, the ability to distinguish between different tumours and provide more reliable diagnoses with precise prognoses has equally increased (Koestner and Higgins 2002). In fact, more reliable prevalence data could be achieved if all reported studies applied IHC in their research (Pezzanite et al. 2015). No antigenic markers are specific for PNST. However, most MPNST react positively to S100 protein in approximately 50– 90% of cases (Gupta and Maniker 2007; Guo et al. 2012). Other antibodies such as factor VIII may react negatively as in a case of pleomorphic corneal sarcoma resembling MPNST in a horse (Kappe et al. 2009). Even in man, the association of nervous and vascular cell tumours has been rarely described as reports of sarcomatous neoplasia with endothelial differentiation areas, similarly to that has been observed in this study (Mentzel and Katenkamp 1999). Based on the morphological features and co-expression of vimentin and S100 protein in the neoplastic cells supports the diagnosis of a MPNST with expression of endothelial differentiation markers. The standard therapeutic protocol in MPNST cases consists primarily of tumour excision with wide security margins whenever the extension and access to the neoplasm permits. However, recurrence is especially common in horses, frequently demanding several surgeries (Koestner and Higgins 2002). Adjuvant therapies are currently being evaluated and some studies have proven successful, especially chemotherapy, radiotherapy and brachytherapy (Saulez et al. 2009), but tumour malignancy degree and financial issues are often an obstacle. The present study reports a MPNST in a horse, while making clear that a wide diagnostic approach may be necessary to conclude the investigation. Malignant peripheral nerve sheath tumour remains rare in domestic animals, but this case indicates this type of tumour should be included in the differential diagnosis of horses with proliferative and ulcerative dermatological lesions accompanied by systemic debilitation. Moreover, to the best of our knowledge, this is the first case of a metastatic MPNST with expression of endothelial differentiation markers described in the equine species.
Malignant peripheral nerve sheath tumour with metastasis
Ethical animal research This case report serves to describe the clinical, pathological and immunohistochemical findings related to a MPNST with expression of endothelial differentiation factors in a horse. The case management was not altered by the study and no ethical approval was obtained.
Source of funding None.
Authorship res, A.C.L. Ca ^ mara and A.R. Teixeira-Neto contributed C.S. Boue to clinical, laboratory and radiographic examinations. M.B. Castro, E.F.G. Barbosa, C.A. Souza and R. Serakides performed the pathological and immunohistochemical examinations. C.S. res, A.C.L. Ca ^ mara, M.B. Castro and R. Serakides drafted Boue the manuscript and all authors critically revised the manuscript and gave it their final approval.
Manufacturers' addresses 1 2
Dako, Carpinteria, California, USA. Sigma Chemical Co., St. Louis, Missouri, USA.
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Authors’ declaration of interests
Nikolaou, G., Bont, M.P., Herden, C. and Hetzel, U. (2015) Paravertebral malignant peripheral nerve sheath tumor (MPNST) in a horse. Equine Vet. Educ. 27, e25-e29.
The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.
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