P36.02 A Case of Recurrent Giant Malignant Solitary Fibrous Tumour of the Pleura: An Elephant in the Room?

Abstract

Solitary fibrous tumor of the pleura (SFTP) is a rare soft tissue neoplasm, accounting for 4% of chest tumors. The biological behavior of SFTP is generally benign, with 10-15% of SFTP that show malignant features with unpredictable long-term behavior. A 59-year-old Caucasian woman with no history of previous malignancies or comorbidities arrived at our institution with cough, increasing dyspnoea, and chest pain. A chest CT scan showed a giant intra-thoracic mass (25x16x16 cm) partially occupying the right hemithorax (fig.1A). Total body 18F-FDG/PET-CT showed a very inhomogeneous mass pattern, with necrotic areas and areas with various patterns of enhancement. A transthoracic FNAB revealed pulmonary SFTP. After cardio-respiratory complete assessment and tumor board evaluation, the patient underwent surgical excision of the mass en-bloc with right upper lobe by thoracotomy. Microscopically, the tumor showed solid spindle cells with high mitotic activity (5 mitoses/10 HPF), high Ki67 expression, and CD34, bcl2, and STAT6 positive. According to England’s criteria, the diagnosis was indicative of a giant malignant SFTP, and the tumor had a Tapias score of 5, which indicated a high risk of recurrence. The postoperative course was uneventful, and the patient was discharged on 8th postoperative day. Due to R0 resection, no adjuvant radiotherapy or chemotherapy was administered, and a strict follow-up was conducted. After 72 months of follow-up, the patient experimented local pleural recurrences (fig.1B) traded with surgical excision in re-thoracotomy. The histopathological analysis showed eight lesions with a median diameter of 1.5 cm, microscopically composed by spindle cells with 10 mitoses/10 HPF, STAT6+, CD34+. Although R0 resection was achieved, adjuvant chemotherapy was administered. A genome sequencing with the next generation approach was performed on the primary lesion and the recurrent disease. SFTP is a rare neoplasm with unpredictable biological behavior. The surgical resection represents the gold standard if complete resection can be reached. The recently introduced Tapias score can be helpful to assess the risk of recurrence: a strict and long-term follow-up should be conducted in case of a high score (>3). In case of local relapse, surgical excision remains the best therapeutic option.