Primary Chest Wall Ewing Sarcoma with Indolent Behavior in an Elderly Male

Abstract

Abstract Introduction/Objective Ewing sarcoma (ES) is the second most common primary malignant bone tumor, primarily affecting children and young adults within the first two decades of life. Over 80% of cases are positive for CD99 and exhibit a characteristic t(11;22) translocation resulting in an EWSR1::FLI1 fusion. Extraosseous ES is extremely rare and most reported cases occur in patients less than 50 years old. We report an unusual case of extraosseous ES arising from the chest wall in an elderly male that showed slow interval progression on imaging studies. Methods/Case Report An 83-year-old male with a past medical history of COPD and tobacco use presented to the emergency department for a mechanical ground level fall and a worsening cough over the prior week. Of note, he was found to have a 6.1 cm pleural based mass seven years prior. The patient was ultimately discharged home with recommended oncologic follow-up for this long-standing chest wall mass due to an increase in size on imaging. A PET scan showed a hypermetabolic subpleural mass in the right lower chest wall measuring 7.6 cm with invasion through the adjacent ribs and intercostal spaces into the adjacent soft tissue. A core biopsy was performed, which demonstrated a small round blue cell tumor diffusely positive for CD99 and Bcl-2, lacking significant mitotic activity and necrosis. Given the unusual clinical features, a next generation sequencing (NGS) panel for sarcoma fusions was performed and identified an EWSR1::FLI1 fusion, supporting the diagnosis of ES/primitive neuroectodermal tumor (PNET). Results (if a Case Study enter NA) NA Conclusion ES is relatively common as a primary bone tumor in children and young adults, but is rare in the chest wall and pleura and is extremely rare in the elderly. The clinical course for ES is typically aggressive. Diagnosis of ES can be challenging as CD99 positivity is nonspecific. The characteristic t(11;22) EWSR1::FLI1 fusion can be identified through FISH or NGS. At 83 years old, this is, to our knowledge, the oldest patient reported in the literature with this diagnosis. The slow interval growth of this mass over a period of seven years is also unusual. These combined clinicopathologic features are exceedingly unique and expand upon the reported spectrum and behavior of the Ewing’s family of sarcomas. The use of broad NGS panels among pathologists may result in increased identification of ES in unusual clinical settings in the future, while also providing more confident pathologic classification in challenging situations.