Table 1.

Liposarcoma classification

	Clinical	Image (CT/NRM)	Anatomopatho­logical	Molecular characteristics	Global survival rate	Relapse rate / Metastasis rate
Atypical lipoma	Painless, soft tu­mor. Slow growth. Most common locations: extremi­ties and retroper­itoneum. Most common subtype	Encapsulated lipomatous mass (hyperintense in T1 and in T2 in NMR) with thick septations	Proliferation of mature adipocytes, with size variation, focal nuclear atyp­ia, and/or fusiform cells	Amplification of MDM-2 and CDK-4	76-93%	(R) - 13-46% (extremities) (R) - 91% (retroperitone­um) (M) - almost zero
Undifferentiated LPS	May result from an atypical lipoma (10%). More frequent in retroperitoneum and extremities	Loss of signal in­tensity in images in T1 and focal nodules (>1 cm is suggestive)	Abrupt transition between mature adipocytes and high degree non-li­pogenic sarcoma areas	Amplification of MDM-2 and CDK-4	54-64%	(R) - 18-57% (M) - 13-47%
Myxoid/ round cell LPS	Tumors more common in lower limbs. Affects young adults more frequently	Hypointensity of the signal in T1, and hyperin­tensity in T2 are pathognomonic	Predominance of round cell myxoid stroma. There is vascular system of thin walls (plexi­form pattern)	FUS-CHOP gene fusion. Mutations PI3K (20%)	40-75%	(R) - 7-28% (M) - 10-58%
Pleomorphic LPS	Rapid growth tumor. More frequent in old people and on extremities	Nonspecific mass, with frequent necrosis and hem­orrhage necrosis	Intense cell atypia, irregular lipoblast. Hyperchromatic nuclei	Complex structural rearrangements	0-63%	(R) - 16-45% (M) - 32-44%

Abbreviations: LPS=Liposarcoma; CT= Computed tomography; NMR= Nuclear magnetic resonance; RT=Radiotherapy