Clinicals, macroscopics and microscopics aspects of the malignant tumor of the peripheral nerve sheath in the brachial plexus of a dog

Malignant peripheral nerve sheath tumor (MPNST) is an infrequent type of sarcoma in dogs, representing a small portion of sarcomas in this species. Considering the rare occurrence of this tumor, combined with the challenges in establishing a definitive diagnosis, this study aimed to discuss the clinical, macroscopic, and microscopic aspects of this neoplasm in a dog through a case report. The patient exhibited lameness in the right thoracic limb and intense pain, even with continuous administration of analgesics and anti-inflammatory drugs. Computed tomography revealed an amorphous and heterogeneous structure in the right axillary region. Surgical excision and intraoperative biopsy were performed, confirming sarcoma. Due to the malignancy and invasiveness of the tumor, which was interwoven within the brachial plexus, shoulder disarticulation was performed. Macroscopically, the tumor was irregular, firm, and whitish/grayish. Histopathological examination suggested MPNST, characterized by a poorly defined neoplasm arranged in bundles, with epithelioid to elongated cells, pleomorphism, mitosis, and necrosis. Postoperatively, the patient continued to experience intense pain and proprioceptive deficits in the pelvic limbs. A follow-up computed tomography scan revealed a heterogeneous structure invading the neural foramen of the first thoracic vertebra and rib resorption. Given the poor prognosis, the owner opted for euthanasia. Despite its infrequent occurrence, MPNST should be included in the differential diagnosis of orthopedic and neurological conditions in dogs due to the importance of early diagnosis and surgical intervention in improving the quality of life.