Pleomorphic Liposarcoma Arising in the Neck with Myxoid/Round Cell Features Showing DDIT3 Amplification

Pleomorphic liposarcoma (PLPS) is the most rare type of LPS, accounting for fewer than 15% of LPSs. It usually presents in older adults and is most commonly located in the retroperitoneum or deep soft tissue of the extremities. PLPS is a high-grade sarcoma with 1/3 showing local recurrence and having overall 5-year survival rate of 55%-65%. We report a case of an epithelioid PLPS in a 68-year-old African-American man, presenting with a rapidly growing painless neck mass developing over 4 months. A fine needle aspiration showed sarcoma composed of multivacuolated epithelioid cells with patchy S100 protein expression and stromal myxoid change. FISH study for DDIT3 rearrangement was negative ruling against a diagnosis of myxoid/round cell liposarcoma. Imaging studies for staging revealed tumor invasion into the middle and posterior scalene muscle and the levator scapulae muscle without involvement of cervical lymph nodes or distant metastases. The mass was widely resected with negative margins. Necrosis and increased mitotic activity characteristic of a high-grade sarcoma were present. Histologically, the tumor showed bizarre lipoblasts, sheets of mono-, bi-, and multivacuolated epithelioid lipoblasts, and pleomorphic spindle cells next to areas with myxoid change, stromal round cells, and delicate plexiform vessels reminiscent of myxoid liposarcoma. Thus, pleomorphic myxoid LPS, described in infants and children, was a consideration. However, this case had amplification of DDIT3 (CHOP) by FISH, more than 10 copies per cell in the pleomorphic areas, which supported a diagnosis of PLPS Grade 3/3 over pleomorphic myxoid/round cell LPS, which typically expresses a reciprocal translocation of DDIT3. This case emphasizes the utility of molecular studies in confirming the diagnosis of an uncommon PLPS in an unusual location.