Dedifferentiated Liposarcoma of the Deep (Paralaryngeal) Soft Tissue: Lessons Learnt from a Case with a Partly Deceptively Benign Appearing Dedifferentiated Component

Abstract

We present a case (female, 61 years of age) of dedifferentiated liposarcoma of the deep, cervical (paralaryngeal) soft tissue with a significant myxoid component and characteristic immunohistochemical (strong and diffuse expression of p16, mdm2 and cdk4 in both the well differentiated liposarcomatous and dedifferentiated components) and molecular genetic findings (MDM2-gene amplification on fluorescence in situ hybridization). The myxoid component which was present in the well differentiated liposarcomatous component gave the tumor atypical radiological features. The case presented initial diagnostic difficulties, mainly because of the bland histomorphological appearance of the limited biopsy material from the sampled non-lipogenic, dedifferentiated component. The dedifferentiated part of the tumor turned out to harbor significant heterogeneity with regards to cellularity, cytomorphology and proliferative activity.

Ultrasound‐guided fine‐needle aspiration of a posterior neck dedifferentiated liposarcoma with MDM2 fluorescence in situ hybridization performed on a Pap‐stained smear

“…The presence of lipoblasts or ALT/WDL is neither required nor sufficient for diagnosis of DDL . Prominent myxoid stroma has been described, as seen in our case, and ∼5–10% of cases demonstrate heterologous differentiation (e.g., myogenic, osteosarcomatous, or chondrosarcomatous) …”

“…DDL is defined by the WHO as ALT/WDL showing progression to a usually non‐lipogenic sarcoma of variable histological grade and differentiation . Up to 20% of ALT/WDL will dedifferentiate and 90% occur within the primary tumor.…”

“…The key feature of DDL is the often abrupt transition between an ALT/WDL to a non‐lipogenic sarcoma that commonly is high‐grade (90%) and resembles an undifferentiated pleomorphic sarcoma; however, approximately 10% of tumors demonstrate low‐grade dedifferentiation (e.g., meningothelial‐like whorls) . The extent and pattern of dedifferentiation is variable and does not predict outcome .…”

“…At least 40% of DDL cases recur locally and distant metastasis is seen in 15–20% of cases; however, DDL, in general, has a less aggressive clinical course than other high‐grade sarcomas including pleomorphic liposarcoma . The anatomic site of DDL is the most important prognostic factor and similar to ALT/WDL, retroperitoneal DDL has the worst prognosis .…”

Primary mediastinal dedifferentiated liposarcoma resected by lateral thoracotomy with video-assisted thoracoscopic surgery

“…Nevertheless, in rare cases, the transition from well-differentiated liposarcoma to dedifferentiated liposarcoma cannot be observed histologically. Recently, immunohistological and/or molecular analyses have been used to confirm the diagnosis, to show overexpression of proteins or amplification of CDK4 and MDM2 genes on chromosome 12q [ 3 , 7 ].…”