Ewing sarcoma of the rib with a rare PTEN mutation.

BACKGROUND

Rib involvement in Ewing sarcoma (ES) is very rare (3-5 %) and may often lead to unique presentations due to mass effect within the thorax. Molecular studies may sometimes offer insights into disease prognosis and possible targeted treatment approaches.

CASE PRESENTATION: Here we present the case of a 39-year-old female who presented with shortness of breath from a massive primary tumor in the right rib and lung. She was diagnosed with ES, which was confirmed by the presence of EWSR1/FLI-1 rearrangement and received multimodal therapy with neoadjuvant VDC-IE (vincristine-doxorubicin-cyclophosphamide, and ifosfamide-etoposide) followed by surgical excision after partial response, and adjuvant chemoradiation. Unfortunately, the patient experienced histologically confirmed local and distant recurrence after several months. NGS of the recurrent tumor revealed a pathogenic PTEN c.640C>T(p.Q214*) nonsense variant with a very high variant allele frequency (VAF) of 82.6 % but negative germline assessment. She received several lines of chemotherapy but only demonstrated a short response to the oral multi-tyrosine kinase inhibitor cabozantinib before eventually passing away.

CONCLUSIONS

PTEN mutations in ES, although rare, may result in a higher likelihood of chemotherapy resistance and poor prognosis. Clinical studies targeting specific molecular traits of these tumors, such as PTEN inactivation, could help improve outcomes in selected cases.