Pleomorphism (microbiology): the ability of some bacteria to alter their shape or size in response to environmental conditions. Dedifferentiated liposarcoma is the least common subtype of liposarcoma and usually arises from a well-differentiated liposarcoma (WDLPS). Progression occurs. in 17 % of patients when WDLPS is located in the retroperitoneum and 6% of cases when WDLPS is located in the extremities.