Table 2.

Clinico-pathologic features of novel round cell sarcoma subtypes.

Differential Diagnosis
EWSR1-NFATC2 and FUS-NFATC2 Sarcoma Mostly long bones Children and adults, M>F Round/spindle cells in hyaline background Variable expression of CD99, PAX7, NKX2.2, AE1/AE3 Local recurrence and distant metastasis	C/C-Rearranged Sarcoma Trunk and extremities Young adults, M>F Diffuse sheets of undifferentiated round to ovoid cells, intervening fibrous stroma; common necrosis, high mitotic rate Expression of WT1 and ETV4; limited CD99 T(4;19)(q35;q13) or t(10;19)(q26;q13) resulting in CIC-DUX4 fusion Very aggressive, poor prognosis	BCOR-Rearranged Sarcoma Bone and soft tissue Children, M>F Primitive small round to ovoid cells solid sheets or nested; variable mitotic rate, rare necrosis Expression of BCOR and/or CCNB3; variable CD99 Inv(X)(p11) resulting in BCOR-CCNB3 fusion Aggressive, poor prognosis
EWSR1-PATZ1 Sarcoma Mostly chest wall Wide age range, F=M Small round/spindled cells, fibrous stroma Variable expression of myogenic and neurogenic markers, CD34 Local recurrence and distant metastasis