A Diagnosis to Wrestle With: Intraventricular Angiomatoid Fibrous Histiocytoma

We report a case of a 15-year-old boy who presented with an intraventricular angiomatoid fibrous histiocytoma. The patient suffered a concussion during a wrestling match and underwent a head and spine CT, which prompted an MRI. MRI revealed an enhancing 2.3-cm mass in the posterior horn of the right lateral ventricle with no hydrocephalus. The patient subsequently admitted to having had headaches with associated appetite suppression but no visual problems or weakness. The tumor was resected. It was composed of sheets and cords of histiocytoid cells with focal pleomorphism. Interspersed throughout was a robust lymphoplasmacytic infiltration with Russell bodies and lymphoid follicles. The histiocytoid neoplastic cells were desmin, EMA, and sparsely S100 protein positive. They were negative for CD31, CD34, Cam 5.2, CD163, CD1a, HMB45, Melan-A, progesterone, and ERG. The abundant plasma cell population was confirmed by CD138 reactivity and was polyclonal by kappa and lambda immunohistochemistry. Fluorescence in situ hybridization revealed an EWSR gene rearrangement. The patient was radiographically free of disease 3 years after surgery with headaches as residual sequela. The differential diagnosis for this case included a lymphoplasmacyte-rich meningioma or a plasmacytoma. The EWSR rearrangement made both of these unlikely. The polyclonal nature of the plasma cell component and the age of the patient also argued against plasmacytoma. A literature search revealed one other ventricular-based angiomatoid fibrous histiocytoma in a pediatric patient.