Recommended Citation
Rizvi H, Smith GP, Macdonald W. The Picture Tells the Story: Multimodality Imaging Unmasks Dedifferentiated Liposarcoma. Presented at Scientific Day; May 20, 2026; Milwaukee, WI.
Abstract
Introduction/Background:
Lipomatous tumors span a spectrum from benign lipoma to atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and dedifferentiated liposarcoma (DDLPS), with significant radiologic overlap. Because DDLPS carries higher morbidity and may coexist with additional malignancies, early recognition of malignant imaging features is essential. This case highlights the critical role of CT and MRI in distinguishing malignant from benign adipocytic tumors and in identifying dedifferentiation within a long-standing extremity mass.
Description:
A 77-year-old man presented with a posterior–medial thigh mass that had enlarged slowly over ~20 years before accelerating with new distal swelling. CT showed a 37-cm predominantly lipomatous mass with thick septations and two enhancing nonfatty nodules concerning malignancy. MRI demonstrated heterogeneous enhancement of a dominant 13-cm nodule, prominent septations, and low-fat regions suggesting hemorrhage, necrosis, or dedifferentiation. These findings guided biopsy of the enhancing nodule, which revealed lipoblasts, atypical multinucleated tumor cells, and myxoid stroma; MDM2 amplification confirmed at least ALT/WDL. Pre-operative CT chest/abdomen/pelvis performed to screen for additional malignancies showed a left adrenal nodule and a right thyroid nodule. Surgical resection demonstrated a focus of dedifferentiation within atypical lipomatous tumor, and external review confirmed DDLPS. Post-surgical PET/CT showed hypermetabolic activity in the adrenal nodule, prostate gland, and soft-tissue irregularity in the thigh surgical bed, guiding post-op management.
Discussion:
This case emphasizes the essential role of multimodality imaging in raising suspicion for malignancy and detecting dedifferentiation in large lipomatous tumors. Thick septations, large enhancing nonfatty nodules, and heterogeneous MRI signal significantly increased the likelihood of malignancy and enabled targeted biopsy of the highest-risk area. Imaging also supported screening for associated malignancies, an important consideration in DDLPS. Although current evidence is limited, systematic analyses consistently support these imaging characteristics as reliable indicators of ALT/WDL and DDLPS. Radiomics, supported by large datasets such as the NETSARC+ registry, represents a promising direction for improving diagnostic accuracy and risk stratification in the evaluation of lipomatous tumors even before biopsy results.
Presentation Notes
Presented at Scientific Day; May 20, 2026; Milwaukee, WI.
Full Text of Presentation
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Document Type
Poster
Open Access
Available to all.
The Picture Tells the Story: Multimodality Imaging Unmasks Dedifferentiated Liposarcoma
Introduction/Background:
Lipomatous tumors span a spectrum from benign lipoma to atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and dedifferentiated liposarcoma (DDLPS), with significant radiologic overlap. Because DDLPS carries higher morbidity and may coexist with additional malignancies, early recognition of malignant imaging features is essential. This case highlights the critical role of CT and MRI in distinguishing malignant from benign adipocytic tumors and in identifying dedifferentiation within a long-standing extremity mass.
Description:
A 77-year-old man presented with a posterior–medial thigh mass that had enlarged slowly over ~20 years before accelerating with new distal swelling. CT showed a 37-cm predominantly lipomatous mass with thick septations and two enhancing nonfatty nodules concerning malignancy. MRI demonstrated heterogeneous enhancement of a dominant 13-cm nodule, prominent septations, and low-fat regions suggesting hemorrhage, necrosis, or dedifferentiation. These findings guided biopsy of the enhancing nodule, which revealed lipoblasts, atypical multinucleated tumor cells, and myxoid stroma; MDM2 amplification confirmed at least ALT/WDL. Pre-operative CT chest/abdomen/pelvis performed to screen for additional malignancies showed a left adrenal nodule and a right thyroid nodule. Surgical resection demonstrated a focus of dedifferentiation within atypical lipomatous tumor, and external review confirmed DDLPS. Post-surgical PET/CT showed hypermetabolic activity in the adrenal nodule, prostate gland, and soft-tissue irregularity in the thigh surgical bed, guiding post-op management.
Discussion:
This case emphasizes the essential role of multimodality imaging in raising suspicion for malignancy and detecting dedifferentiation in large lipomatous tumors. Thick septations, large enhancing nonfatty nodules, and heterogeneous MRI signal significantly increased the likelihood of malignancy and enabled targeted biopsy of the highest-risk area. Imaging also supported screening for associated malignancies, an important consideration in DDLPS. Although current evidence is limited, systematic analyses consistently support these imaging characteristics as reliable indicators of ALT/WDL and DDLPS. Radiomics, supported by large datasets such as the NETSARC+ registry, represents a promising direction for improving diagnostic accuracy and risk stratification in the evaluation of lipomatous tumors even before biopsy results.
Affiliations
Aurora St. Luke's Medical Center, Aurora Sinai Medical Center