PMC8794306_01
Histomorphology of myxoid and round cell liposarcoma. (A) Myxoid liposarcoma is characterized by a paucicellular proliferation of small round tumor cells embedded in abundant myxoid stroma (10x magnification, H&E); (B) higher magnification of myxoid liposarcoma shows a characteristic branching pattern of small vessels resembling "chicken-wire" (40x magnification, H&E); (C) high-grade myxoid liposarcoma ("round cell liposarcoma") shows a dense, hypercellular proliferation of small round blue cells with minimal to completely absent myxoid stroma (10x magnification, H&E); (D) transitions between low-grade myxoid liposarcoma (top left) and high-grade round cell liposarcoma (bottom right) (4x magnification, H&E).
med-04-27-f5.jpg
PMC8794306_01_med-04-27-f5.jpg
f5
The histology of low-grade MLS is characterized by sheets of small round to oval cells with small nuclei, scant cytoplasm and very low mitotic activity (Figure 5A). The cells are suspended in an abundant myxoid stroma that contains an arborizing network of delicate small branching vessels resembling chicken wire (Figure 5B). The high-grade tumors showed compact sheets of round blue cells with round nuclei containing small nucleoli and scant cytoplasm (Figure 5C). The stroma varied from areas that were myxoid to hypercellular areas devoid of any myxoid stroma; transitions between hypercellular areas composed entirely of small round blue cells and areas that were myxoid could be often encountered (Figure 5D).
Nuclear atypia in pleomorphic liposarcoma. (A) Pleomorphic liposarcoma shows sheets of large pleomorphic tumor cells resembling undifferentiated pleomorphic sarcoma (40x magnification, H&E); (B) higher magnification of pleomorphic liposarcoma shows a large multivacuolated lipoblast (center); identification of these cells is indispensable for the diagnosis (40x magnification, H&E).
med-04-27-f6.jpg
PMC8794306_01_med-04-27-f6.jpg
f6
The tumor has been defined as a high-grade pleomorphic sarcoma that contains a variable number of pleomorphic lipoblasts in the absence of a WDL/ALT component (Figure 6A,B).
Thymoliposarcoma. (A) Scanning magnification of thymoliposarcoma shows entrapped residual thymic epithelium surrounded by a sheath of fibrous tissue and mature stromal fat (4x magnification, H&E); (B) higher magnification of thymoliposarcoma shows branching small island of thymic epithelium surrounded by connective tissue and fat containing a few enlarged, atypical and hyperchromatic lipoblastic cells (40x magnification, H&E).
med-04-27-f7.jpg
PMC8794306_01_med-04-27-f7.jpg
f7
This is a term coined by Havlicek and Rosai in which a WDL appears to be arising within the stromal fatty compartment of the thymus; it was therefore interpreted as a true primary liposarcoma arising from the thymus (Figure 7A,B).
PMC8794306_02