Giant Malignant Schwannoma in the Right Thoracic Limb: Case Report

ABSTRACT


INTRODUCTION
Schwannomas, or also known as neurilenomas, are benign tumors derived from the myelin sheaths of peripheral nerves and represent approximately 5% of soft tissue tumors of the upper limb. 1,4They occur spontaneously and are mainly associated with family history.with neurofibromatosis type 2, schwannomatosis and Carney complex. 3According to the World Health Organization, they are grade I tumors and very rarely become malignant, mainly in malignant tumors of the peripheral nerve sheath or angiosarcoma.

CLINICAL CASE
A 62-year-old male, pensioner, with a significant history of schizophrenia diagnosed 10 years ago on treatment with clozapine, benign prostatic hyperplasia for 3 years on treatment with tamsulosin, hypercholesterolemia for 3 years on treatment with pravastatin.Positive smoking at a rate of 1 pack a day for 50 years, stopped 1 month ago, with a smoking index of 50.He denies any history of surgery or allergies.
Image 1. Ulcerated solid tumor on the posterior aspect of the right thoracic limb.Corresponding Author: Narváez Villanueva Juan Manuel He refers to starting 8 months ago with the presence of a tumor less than 1 cm in the posterior region of the right elbow, painless, with a subsequent increase in size and involuntary weight loss of approximately 30 kg in 8 months, which is why he went for evaluation by oncological surgery where On physical examination, a solid tumor was identified in the region behind the right elbow, fixed, painless, with irregular edges of approximately 15 cm by 15 cm, with a non-bleeding ulcer in the center.No axillary, cervical, or inguinal lymph nodes are palpable.A CT scan of the right thoracic limb was requested, reporting a solid tumor of 11.4 x 9.5 cm dependent on the triceps muscle with a poorly defined hypodense area, accompanied by acute inflammation of all the fatty tissue and thickening of the skin (Images 2-3).Closed biopsy with Trucut 16G was performed with histopathological report of highgrade malignant spindle cell neoplasm.Therefore, wide resection is electively decided.Normal preoperative laboratories Images 2-3.CT scan of the right thoracic limb reporting a solid tumor measuring 11.4 x 9.5 cm dependent on the triceps muscle with a poorly defined hypodense area, accompanied by acute inflammation of all the fatty tissue and thickening of the skin.

Surgical technique
Preoperative marking was performed with 2 cm margins (image 1), then a spindle incision was made with a 3:1 ratio of the lesion, it was approached by planes, dissecting with wide margins, predominantly between the triceps brachii muscle fibers, performing complete resection of the lesion (images 4-5).Widely, 2 cm perilesional undermining was performed, a ¼-inch Drenovac type drain was placed, subcutaneous and deep tissue was faced with simple separated sutures with 2-0 vicryl and skin was faced with 2-0 nylon with Sarnoff stitches.Currently under follow-up by Medical Oncology for adjuvant treatment with radiotherapy.The histopathological report described a lesion with a white nodular appearance, firm in consistency, neoplastic in appearance, measuring 12.3 cm by 9.5 cm, with a capsule of loose fibroconnective tissue, lobulated in appearance with central areas of fibrous appearance, diagnosing grade 2 ulcerated malignant Schwannoma of the French classification of sarcomas, free surgical margins and no evidence of lymphovascular infiltration.
Image 6. Postoperative wound closure with Sarnoff type suture and placement of DRENOVAC.

DISCUSSION
Malignant schawannoma, also known as neurofibrosarcoma, neurogenic sarcoma, malignant neurilemoma, or malignant peripheral nerve sheath tumors, is a rare entity, with an approximate incidence of 0.001% in the population. 8lthough schawannomas are the most common type of benign nerve sheath tumors.Only a very small number of peripheral nerve sheath tumors have been previously reported as schwannomas. 10This phenomenon was first reported in 1994 by Woodruff et al., 11 who reported 2 cases of peripheral malignancy of nerve sheath tumors.The malignant lineage is a rare malignant mesenchymal lesion with a prevalence of 5% of all soft tissue sarcomas. 6These are mainly related to autosomal dominant genetic syndromes such as neurofibromatosis types 1 and 2. 3, 5 It has been described that patients with neurofibromatosis type 1 have greater risk of malignant transformation in pre-existing plexiform neurofibroma. 8In general, they are known to have high metastatic potential and poor prognosis.Multiple series of studies report a 5-year survival of 15-50%. 9The most common sites involve nerve roots and bundles in the extremities and pelvis, mainly the sciatic nerve.Up to 50% of patients have metastatic disease, mainly to the lung. 9Cai et al. reported that the location with the highest risk of poor prognosis is in the head and neck compared to the location in the extremities. 6Most schwannomas are asymptomatic, such as pain, weakness and paresthesias.Due to its presentation in the upper extremities, it is common to initially think of other differential diagnoses such as lipomas, synovial cysts, ganglions and other pathologies. 2Magnetic resonance imaging is the most useful imaging study to determine the anatomic extent and the surgical plan.In the setting of localized disease of soft tissue sarcomas, complete surgical excision with clear margins is the treatment of choice.Tumor size (considered larger than 5 cm) is considered the most determining prognostic factor in the literature.Other factors reported are tumor grade, truncal location, surgical margins, local recurrence, and heterologous rhabdomyoblastic differentiation. 9Free margins are of vital importance for the control of local recurrence, as well as survival. 4Therefore, according to the literature, free margins are a protective factor for a better prognosis. 6

Images 4 and 5 .
Resected tumor with 2-cm margins and its relationship with the surgical bed.Integrity of the ulnar nerve can be observed.Corresponding Author: Narváez Villanueva Juan Manuel During the postoperative period, blood flow was approximately 50 cc per day.Discharged with adequate improvement two days after the operation, withdrawing the DRENOVAC at 7 days with little serous output.(Image 6).