Magnetic resonance imaging features of RB1-deleted adipocytic neoplasms in a survivor of bilateral retinoblastoma

Atypical spindle cell/pleomorphic lipomatous tumor and dysplastic lipoma are closely related fatty masses associated with RB1 abnormalities. While it is not yet widely agreed that they are separate entities, the distinct morphological features of dysplastic lipomata and divergent anatomic distribution suggest that this is probable. RB1 abnormalities are present in spindle cell/pleomorphic lipoma, pleomorphic liposarcoma, and pleomorphic liposarcoma with or without myxoid component. Survivors of hereditary retinoblastoma, caused by germline mutations in the RB1 gene, have a substantially increased risk of developing benign and malignant lipomatous tumors including atypical spindle cell/pleomorphic lipomatous tumor and dysplastic lipoma. This report describes the MRI findings of several such lesions in a survivor of bilateral retinoblastoma including features such as enhancement that might otherwise be concerning for higher-grade malignancy.