Dedifferentiated liposarcoma primary to the chest wall with spontaneous shrinking: report of a case.

An 80-year-old man presented to our emergency department complaining of a mass on the right side of his chest and pain in the right flank of his back. A chest computed tomography (CT) scan showed a relatively heterogenous oval-shaped tumor measuring 7.5 × 6.0 cm eroded to the 8th rib, with slightly dense fluid accumulation inside and calcification of the tumor wall. A 1-month follow-up CT scan showed spontaneous shrinkage of the tumor. The tumor was completely excised from the thoracic wall and the wall was reconstructed with a polytetrafluoroethylene mesh. Pathological examination showed coagulation necrosis in the chest wall tumor, but immunohistochemical staining revealed murine double minute 2- and Cyclin-dependent kinase 4-positive cells with irregular nuclear size and bizarre morphology. Therefore, dedifferentiated liposarcoma (DDLPS) was the final pathological diagnosis. Remarkable infiltration of CD8+ lymphocytes into the tumor was observed, along with a 90% positive ratio for programmed cell death-ligand 1. The patient has been followed-up for 1 year without any recurrence, despite not receiving any additional treatment. Liposarcoma is one of the most common types of soft tissue sarcomas; however, spontaneous regression of primary DDLPS arising from the chest wall is extremely rare. Herein, we report a case of DDLPS primary to the chest wall with spontaneous regression, probably due to a spontaneously induced T cell response.