Malignant peripheral nerve sheath tumor originating from the adrenal gland in a dog

Malignant peripheral nerve sheath tumor in the kidney of a dog

A 12-year-old castrated male poodle presented with vomiting and diarrhea. Ultrasonography and computed tomography revealed a protruding mass at the caudal pole of the left kidney. Grossly, the poorly circumscribed abnormal mass was 1.6 × 1.8 × 1.9 cm in size and had multifocal dark-red foci. Microscopically, it was composed of densely or loosely packed variable-sized short spindle or ovoid cells. These neoplastic cells showed high pleomorphism, mitotic figures, and invasive tendency to the adjacent tissue. Immunohistochemically, the neoplastic spindle cells expressed vimentin, S100, neuron-specific enolase, nerve growth factor receptor, and laminin. Therefore, the mass was diagnosed as a malignant peripheral nerve sheath tumor (MPNST). To our knowledge, this is the first report of primary renal MPNST in a dog.

Case report: Presumptive subcutaneous malignant peripheral nerve sheath tumor with intracranial invasion and osteolysis in the posterior fossa of a dog

A 13-year-old castrated male Toy Poodle presented with an acute vestibular disorder. Magnetic resonance imaging and computed tomography revealed a large oval space-occupying mass with skull destruction located from the subcutaneous tissue to the posterior fossa region. Histopathologically, the mass was a bundled growth of spindle-shaped mesenchymal tumor cells between the myofibrillar and collagen bundles. The cells were moderately irregular in size and had eosinophilic stained cytoplasm. The cells were highly atypical and had rare mitotic figures. Neoplastic cells were immunoreactive for S100, GFAP, Olig-2, SOX10 and immunonegative for NF, E-cadherin, and Claudin-1. Collective findings were presumptive with a diagnosis of malignant peripheral nerve sheath tumor.

A rare case of cecal malignant peripheral nerve sheath tumor in a dog

A 12-year-old mixed-breed dog presented with a 2-month history of abdominal distension. Radiographic examination, abdominal ultrasonography, and computed tomography revealed a mass in the cecum (15.0 × 11.9 × 4.5 cm). The cecal mass was surgically removed and examined histopathologically. Immunohistochemically, the neoplastic cells expressed S-100 and neuron specific enolase but not α-smooth muscle actin and CD117 (c-kit). These histologic and immunohistochemical features indicated that the mass was consistent with a malignant peripheral nerve sheath tumor (MPNST). In dogs, most MPNSTs arise from the brachial plexus, spinal nerve root, and skin of the extremities. However, gastrointestinal MPNSTs in dogs have not been described previously. To the best of our knowledge, this is the first report to describe cecal MPNST in a dog.

Histopathological and Immunohistochemical Evaluation of Canine Nerve Sheath Tumors and Proposal for an Updated Classification

Nerve sheath tumors are a group of tumors originating from Schwann cells, fibroblasts, and perineurial cells. In veterinary pathology, the terminology for nerve sheath tumors remains inconsistent, and many pathologists follow the human classification of such tumors in practice. Immunohistochemistry plays an important role in the diagnosis of nerve sheath tumors, but specific immunohistochemical and molecular biomarkers are lacking. In our study, we histopathologically reevaluated 79 canine nerve sheath tumors and assessed their reactivity for the immunohistochemical markers Sox10, claudin-1, GFAP, CNPase, and Ki-67. Based on the results, we classified the tumors according to the most recent human classification. Twelve cases were diagnosed as benign nerve sheath tumors, including six neurofibromas, three nerve sheath myxomas, two hybrid nerve sheath tumors (perineurioma/neurofibroma and perineurioma/schwannoma), and one schwannoma. Sixty-seven tumors were malignant nerve sheath tumors, including fifty-six conventional, four perineural, one epithelioid malignant nerve sheath tumor, and six malignant nerve sheath tumors with divergent differentiation. We believe that with the application of the proposed panel, an updated classification of canine nerve sheath tumors could largely follow the recent human WHO classification of tumors of the cranial and paraspinal nerves, but prospective studies would be needed to assess its prognostic value.

A rare case of malignant vagus nerve sheath tumor presenting with multiple cranial nerve dysfunction in a dog

A 5-year-old intact male Gascon Saintongeois dog was presented with a 6-month history of coughing, laryngeal paralysis, a deglutition disorder of gradual onset, and left-sided Horner's syndrome. The dog was admitted as an emergency for acute central vestibular signs. Magnetic resonance images identified a left extra-axial brainstem lesion extending caudally from the medulla to the vagosympathetic trunk. Histological and immunohistological examination revealed a high grade epithelioid malignant peripheral nerve sheath tumor (MPNST). This case report is the first description of a MPNST of the vagus nerve compressing the brainstem and causing multiple cranial nerve dysfunction in a dog. Key clinical message: Nerve sheath tumors have been reported in many locations arising from spinal nerve roots and cranial nerves. Although the trigeminal nerve is the most commonly affected nerve, other cranial nerves such as the vagus can be affected.

Four Cases of the Melanotic Variant of Malignant Nerve Sheath Tumour: a Rare, Aggressive Neoplasm in Young Dogs with a Predilection for the Spinal Cord

Four cases of a rare melanotic variant of malignant nerve sheath tumour (MNST) in dogs are described. All four cases presented with neurological clinical signs due to multicentric, intradural, intra- and extraparenchymal neoplasms that surrounded the spinal and cranial nerves and infiltrated the adjacent spinal cord and brain. The dogs were young (3 months to 3 years of age), all were female and four different breeds were represented. Characteristic histological features were interweaving fascicles of spindle-shaped cells, sometimes with an architecture reminiscent of Antoni A and B patterns. Some spindle cells showed prominent cytoplasmic melanin pigmentation and such cells were positive by Masson-Fontana stain. Immunohistochemistry performed in three cases was positive for S100 and vimentin, strongly positive for melan A in the melanized cells and negative for glial fibrillary acidic protein and periaxin. Non-melanized cells did not express melan A. Transmission electron microscopy findings in one case were consistent with a peripheral nerve sheath tumour and demonstrated cytoplasmic pre-melanosomes and melanosomes. Melanotic variants of MNSTs are rare in animals with only a solitary report of two previous canine cases in the literature.

Colonic malignant peripheral nerve sheath tumour in a cat

Case summary

A 14-year-old male neutered domestic mediumhair cat presented with a 4 month history of inappetence and weight loss. Pertinent abnormalities on haematology and biochemistry included a mild microcytic regenerative anaemia (packed cell volume [PCV] 24% [reference interval (RI) 30–45%], mean cell volume 30.8 fl [RI 40–45 fl], absolute reticulocyte count 326.8 × 10¹²) and increased alkaline phosphatase activity (76 IU/l; RI <50 IU/l). Abdominal ultrasound and CT scan revealed masses in the transverse colon (2.0 cm × 1.2 cm) and right medial liver lobe (5.0 cm diameter). Thoracic radiographs were unremarkable. Right medial liver lobe resection and colectomy were performed. Immunohistochemistry was positive for S-100 protein, vimentin and glial fibrillary acidic protein, very weakly positive for c-kit and negative for muscle-specific actin and CD18, consistent with a colonic malignant peripheral nerve sheath tumour (MPNST) with a hepatic metastasis. Postoperative treatment with metronomic cyclophosphamide was well tolerated. Eighteen months postoperatively the cat re-presented after 3 days of progressive lethargy and inappetence. Haematology revealed a marked non- or pre-regenerative anaemia (PCV 10%). Coagulation times were prolonged (prothrombin time 39 s [RI 15–22 s] and activated partial thromboplastin time >300 s [RI 65–119 s]). Abdominal ultrasound identified multiple renal and hepatic nodules. Euthanasia was performed and post-mortem examination confirmed metastasis of the MPNST.

Relevance and novel information

This report describes the treatment of a metastatic colonic peripheral nerve sheath tumour in a cat. Feline visceral MPNSTs are rare and little is known about prognosis or optimal treatment.