This case fulfills the criteria for multiple primary malignancies [1], as our patient was simultaneously diagnosed with invasive ductal breast carcinoma (ER+/PR+/HER2+, pT1cN0) and clear cell renal cell carcinoma (pT1aNxMx, G2) following treatment for HL at age 23 with ABVD and supradiaphragmatic radiotherapy. Here, ESR1 is linked to clear cell renal carcinoma.