Background Cancer treatment can cause various long-term side effects, including those that impact ultrasound findings. During follow-up of childhood cancer survivors (CCSs), we often detected sporadic renal angiomyolipomas without histological confirmation (SAMLs), which is why we initiated this study. We compared the occurrence of SAML in CCSs to the previously reported data from a non-cancer population and correlated SAML with cancer treatment-related factors. Methods The cohort included 1098 CCSs (median age at cancer diagnosis (dg) 4.3 years) who had ultrasound follow-up (2014–2019). Of the CCSs, 525 (48%) were female, 132 (12%) had subsequent neoplasms (SNs), and 110 (10%) had genetic syndromes. CCSs were treated for lymphomas 269 (24%) and solid tumors 829 (76%). None of the CCSs had tuberous sclerosis complex (TSC). Results SAML developed in 48 (4.4%) CCSs; of these, 20 (42%) had SNs. The coincidence of SAMLs and SNs was found in CCSs with a follow-up period exceeding 20 years. The median age at SAML dg was 27.9 years (interquartile range (IQR) 22.3–34.1), and the median time to SAML dg was 22.6 years (IQR 17.4–27.6). Twenty-one (44%) CCSs developed multiple or bilateral SAMLs lesions; of these, six (12%) were in the radiotherapy field. SAML occurrence correlated with radiotherapy of the retroperitoneum (1.65-fold higher with 95% CI 0.90–3.02). The correlations with other cancer treatment factors and with female sex were less clear. Conclusion This study revealed the occurrence of SAMLs in CCSs to be 10 times higher than that in non-cancer studies. The current characteristics of CCSs with SAMLs: younger age, and more bilateral or multiple lesions are more similar to TSC associated angiomyolipoma. Moreover, we observed a coincidence of SAMLs with SNs. Our results support the hypothesis that SAML development in CCSs is not simply a late effect of therapy, and indicates other factors are involved in SAML development.