Spontaneous remission of a pulmonary sclerosing epithelioid fibrosarcoma: a case report of a possible abscopal effect.

Background: Spontaneous remission (SR) is defined as the complete or partial disappearance of a diagnosed malignant disease in the absence of known active medical treatment. The role of the immune system is thought to be important, but has not yet been elucidated. On this matter, there are studies that suggest that the abscopal effect (AE), which is defined as the remission of untreated lesions beyond the irradiated area, may be explained by the activation of a systemic immune response against the tumor. Sclerosing epithelioid fibrosarcoma (SEF) is a rare variant of soft tissue sarcoma that is characterized by a slow evolution, with local recurrences and late metastases. The treatment is based on surgery, leaving a minimal role to chemotherapy (ChT) and radiotherapy (RT) for metastatic unresectable disease, and no cases of SR have been reported in the literature so far. Case Description: We present the case of a patient with a lung metastatic recurrence of SEF, diagnosed and treated with surgery 8 years before. After progression to pazopanib and other ChT drugs, because of the chest pain associated with a pleural mass invading the second costal arch, the patient received antalgic local RT treatment. Months later, and without any further treatment, a partial remission of all the tumoral lesions was presented, and she is alive 25 years after the first diagnosis. Conclusions: As far as reported in the literature, this is the first case of SR in SEF. Among the possible causes of this SR, we think that the most plausible is that palliative treatment with RT of the pleural mass induced an AE, leading to a reduction of all tumoral lesions, even those outside the irradiated region.