PLEURAL SPINDLE CELL NEOPLASM IN A PATIENT WITH NEUROFIBROMATOSIS TYPE I

Abstract

SESSION TITLE: Fellows Disorders of the Pleura Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: October 18-21, 2020 INTRODUCTION: A twenty-two year old male with NF1 presented with multiple pleural masses, consistent with spindle cell neoplasm. Given his history, malignant peripheral nerve sheath tumor is suspected and a rare presentation of this disease. CASE PRESENTATION: A twenty-two-year-old male with Neurofibromatosis Type 1 (NF1) presented to the Emergency Department with abdominal pain. Past medical history included malignant peripheral nerve sheath tumor (MPNST) of the left leg. Despite resection, there was local recurrence within one month and the patient subsequently received chemotherapy with ifosphamide and etoposide, radiation, and surgical resection with a below-knee amputation. A one-cm right lower lobe pulmonary nodule with mild FDG avidity was found on surveillance PET scan. An attempted biopsy was unsuccessful due to the location of the nodule. Unfortunately, the patient was lost to followup. He presented six months later with abdominal pain and dyspnea and was found to have a large right pleural effusion with pleural masses causing mediastinal shift (Figure 1). Tube thoracostomy was performed. Pleural fluid analysis showed a lymphocyte-predominant, exudative effusion. Infectious workup, including bacterial and fungal cultures and adenosine deaminase level, was negative. Cytology demonstrated only reactive mesothelial cells. Pleuroscopy was performed, and multiple pleural-based masses (Figure 2) were biopsied and found to be consistent with spindle cell neoplasm. Immunostaining was negative for neurofilament, CD34, STAT6, Bcl-2, SMA and desmin, CD117, Dog-1, Sox-10, ALK-1, beta-catenin. There was rare staining of S100 and WT-1 positivity, with further histopathological workup pending. DISCUSSION: NF1 is an autosomal dominant disorder with variable organ involvement. Mutation in the NF1 gene results in loss of function of the neurofibromin tumor suppressor protein and upregulation of RAS activity leading to increased tumorigenesis. While a benign disorder, the incidence of malignancy in patients with NF1 is increased and is estimated to be around 2-4.1% per lifetime. Malignant transformation in young adults is most often MPNST, a type of spindle cell sarcoma. Pleural involvement, while rare, is often from metastases as suspected in this case. Accurate and early diagnosis has implications for therapy but can be difficult to distinguish from other soft tissue sarcomas as there is no specific molecular signature. Immunohistochemical staining may show weak staining for S-100 protein in 50% of cases. Surgical resection is preferred in localized disease. Metastatic disease is associated with a poor prognosis, with fewer than 40% of patients surviving past one year after diagnosis. CONCLUSIONS: While a benign disease, NF1 is associated with an increased risk of malignant transformation; pleural involvement is rare but should be on the differential diagnosis of a pleural mass associated with NF1. Reference #1: Zhang Y, Chao J, Qin S. Type I neurofibromatosis with spindle cell sarcoma: A case report. World Journal of Clinical Cases 2019;7:3104-3110. Reference #2: Bethany C. Prudner Tyler Ball , Richa Rathore , and Angela C. Hirbe. Diagnosis and management of malignant peripheral nerve sheath tumors: Current practice and future perspectives. Neuro-Oncology Advances 2019; 20: 1–10 Reference #3: Evans DG, B. M., McGaughran J, Sharif S, Howard E, Moran A: Malignant peripheral nerve sheath tumours in neurofibromatosis 1. J Med Genet, 39((5)): 311-4, 2002 DISCLOSURES: No relevant relationships by Edward Bergin, source=Web Response No relevant relationships by Arista Chand, source=Web Response No relevant relationships by Joshua Malo, source=Web Response