Abstract
Introduction: Dedifferentiated liposarcoma (DDLPS) is defined as a progression of well-differentiated
liposarcoma (WDLPS) to another nonlipogenic sarcoma. Since a variety of heterologous
sarcomas can be encountered in dedifferentiation, clinical dilemmas arise. The present
study analyzed the role of clinicopathologic and immunohistochemical (IHC) features
in the diagnosis of DDLPS and its differentiation from mimics. Materials and Methods: A retrospective and prospective study was conducted wherein all cases of liposarcoma
from 2012 to 2017 were reviewed. DDLPS cases were identified among pleomorphic lesions.
Clinical and histopathological details for these cases were retrieved from medical
records section and department archives. Histomorphology and immunohistochemistry
(MDM2, S100, and Ki-67) were analyzed for these cases. Results: Among 37 cases of liposarcomas reviewed, DDLPS was diagnosed in 12 cases (32.4%).
Mean age of the patients was 54.3 years with equal gender distribution (M:F =1:1.2).
Two patients had recurrent tumors. Most were retroperitoneal (58.3%) with mean duration
of symptoms being 8.7 months. Mean tumor dimension was 17.5 cm. High-grade dedifferentiated
component was most common (83.3%) with only one case each (8.3%) of low-grade and
homologous dedifferentiation. Undifferentiated pleomorphic sarcoma was the frequent
nonlipogenic sarcoma. MDM2 overexpression was detected in 100%, focal S100 positivity
seen in 66.6%, and mean Ki-67 labeling index was 24. Conclusion: DDLPS exhibits aggressive clinical behavior. Adequate sampling, correlation to clinical
details, demonstration of transition from WDLPS to DDLPS aid in narrowing the differentials.
Immunostaining with MDM2 helps in definite categorization and S100 highlights lipoblasts,
when they are not easily identifiable. MDM2, CDK4, and p16 IHC panel is recommended
in all cases and fluorescence in situ hybridization analysis where IHC is noncontributory.
Keywords
Dedifferentiated - liposarcoma - MDM2 - sarcoma
