Follicular Dendritic Cell Sarcoma
There is a subset of follicular dendritic cell sarcomas occurring in the liver and spleen that resemble inflammatory pseudotumor but also show focal/weak expression of follicular dendritic cell markers. These tumors are less cellular and the spindle morphology may be obscured by lymphoplasmacytic infiltrate. They occur mainly in females, are more indolent, and are associated with systemic symptoms. They lack ALK expression, unlike in inflammatory myofibroblastic tumor, but show EBV-coded RNA (EBER).