Abstract Background Multiple primary malignant neoplasms are not frequent but are increasing in incidence. Some of them are associated with genetic syndromes such as von Hippel-Lindau syndrome and Li-Fraumeni syndrome. Dedifferentiated liposarcoma is one of the rarest soft tissue tumors, and clear cell renal carcinoma is the most frequent kidney cancer. The concomitant presence of these tumors is extremely rare; however, some cases have been reported, none of them presenting with liposarcoma of the limbs. We report an interesting case of a patient with synchronous multiple primary tumors presenting with a very rare liposarcoma associated with renal cell carcinoma (a very rare association). A review of the literature and a collection of similar cases published previously are also provided. Case presentation We report a case of a 62-year-old Hispanic man who presented to our institution with a left thigh mass compatible with dedifferentiated liposarcoma synchronous with metastatic clear cell renal carcinoma. Multiple treatment lines were provided with no response, with a further metastatic transformation. Genetic analysis by liquid biopsy showed some mutations that were not susceptible to targeted therapy. At the time of this report, the patient is undergoing palliative care because his nonresponsive metastatic disease persists. Conclusions We present the first reported case of clear cell renal carcinoma synchronous with dedifferentiated liposarcoma of a limb. The association between renal cell carcinoma and dedifferentiated liposarcoma is unusual, and there are few reports of this presentation in the literature. More research about these tumors along with genetic tests needs to be performed to seek a better understanding of the fundamental basis of this rare association.