(P 249) TUMOR CELL DISAPPEARANCE FOLLOWING COVID-19 INFECTION IN A PATIENT WITH PLEOMORPHIC SPINDLE CELL SARCOMA: A CASE REPORT

Objective: Tumor regression after COVID-19 infection has been reported in hematological malignancies, but there have been no reports in cases of sarcoma to the best of our knowledge. We present a case of pleomorphic spindle cell sarcoma in which tumor cells disappeared after the patient was infected with COVID-19. We discuss the potential association between COVID-19 and sarcoma and explore the possible mechanisms underlying this phenomenon.

Methods: A 65-year-old male with a history of hypertension and hyperuricemia noticed a right upper arm mass a few years prior to presentation. He sought medical attention at a previous hospital, where CT and MRI revealed a soft tissue tumor. Subsequently, he was referred to our institution for further evaluation and management. A diagnosis of pleomorphic spindle cell sarcoma was established through a needle biopsy. Routine screening tests performed at the time of biopsy incidentally revealed asymptomatic COVID-19 infection. Two months post-infection, a wide resection of the tumor was performed after confirming negative PCR results.

Results: Histopathological examination of the initial biopsy specimen demonstrated pleomorphic spindle cells proliferating in a collagenous background, with immunostaining results suggesting myogenic differentiation. In contrast, the resected specimen obtained two months after COVID-19 infection revealed a striking finding - extensive replacement of the tumor by hyalinized tissue with marked lymphocytic infiltration and a pronounced paucity of tumor cells. The infiltrating lymphocytes were mainly CD3-positive T cells, with a mixture of CD4-positive helper T cells and CD8-positive cytotoxic T cells. Additionally, inflammatory cell infiltration into the vessel walls was noted. These findings suggest tumor cell disappearance and an inflammatory response.

The case presented here is unique in demonstrating tumor cell disappearance in a pleomorphic spindle cell sarcoma following COVID-19 infection. This observation raises the possibility of an association between COVID-19 and sarcoma regression. While the exact mechanisms underlying this phenomenon remain to be elucidated, we hypothesize that the activation of cellular immunity by COVID-19 may have played a crucial role in exerting an antitumor effect. SARS-CoV-2 infection has been shown to elicit a robust T cell response, which could cross-react with tumor antigens and lead to enhanced tumor cell recognition and elimination. Additionally, the inflammatory milieu induced by COVID-19 infection may have contributed to the recruitment and activation of immune cells within the tumor microenvironment, further potentiating the antitumor immune response. However, it is essential to note that the causal relationship between COVID-19 infection and tumor cell disappearance in this case remains uncertain, and further research is necessary to validate these hypotheses.

Conclusion: This case report presents a novel finding of tumor cell disappearance in a patient with pleomorphic spindle cell sarcoma following COVID-19 infection. The potential association between COVID-19 and sarcoma regression, as highlighted by this case, warrants further investigation. Future studies should aim to elucidate the underlying mechanisms and explore the possibility of harnessing the immunomodulatory effects of COVID-19 infection for therapeutic purposes in sarcoma and other solid tumors. Additionally, this case underscores the importance of close monitoring and follow-up of cancer patients who contract COVID-19, as the infection may have unexpected effects on tumor biology and clinical outcomes.