Intraventricular Fibroma: MR and Pathologic Comparison Douglas H. Wright, 1 L. Gill Naul , 1.3 Joseph H. Hise, 1 and S. C. Bauserman 2 Summary: This case report describes clinical, surgical, MR, and pathologic findings of an intraventricular fibroma, a rare, benign mesenchymal neoplasm. Relatively isointense with normal brain parenchyma on Tl-weighted images, the tumor exhibited hyperintense signal on T2-weighted pulse sequences and en- hanced intensely and homogeneously after intravenous admin- istration of gadopentetate dimeglumine. Choroid plexus papil- loma/carcinoma, meningioma, ependymoma, and subependy- mal giant cell astrocytoma should be included in the differential diagnosis. Index terms: Brain neoplasms, magnetic resonance; Brain, ven- tricles; Neuropathology; Radiologic-pathologic correlations Intracerebral fibromas are rare, benign mesen- chymal neoplasms (1, 2). In 1985, Palma et al reported a case of an intracerebral fibroma and reviewed the literature (2). This report describes an intraventricular fibroma in a child. We report clinical, surgical, and magnetic resonance (MR) findings as well as the pathologic features by immunohistochemistry and electron microscopy . Case Report An 11-year-old girl presented with a 6-week history of intermittent vomiting and headaches. Physical examination was normal. MR revealed a 3-cm mass in the trigone of the right lateral ventricle. It was relatively isointense with the adjacent normal brain parenchyma on T1-weighted images, 1000/ 17/2 (TR/ TE/e xcitations) (Fig. 1 A) and of hyperintense signal intensity on T2-weighted image s (2500 /9 0/ 1) (Fig. 1B). The portion of th e right lateral ventricle posterior to the mass was " trapped " as demon- strated by dilatation and signal intensity differing from th e rest of the cerebrospinal fluid , probably due to its high er protein content. The ventricles were otherwise normal in size and signal intensity . Edema was noted in th e brain parenchyma surrounding the mass. The mass enhanced intensely after intravenous injection of gadopentetate di- meglumine (Fig. 1 C). A choroid plexus papilloma was considered the most likely diagnosis preoperativ ely . At surgery , a firm , highly va sc ular enca psulat ed tum or within th e trigone of the ri ght lateral ventricle was removed. The tumor was in timate ly related to adjacent thickened , matted choroid plexus, and the trigone of th e right lat eral ventricle was obstr ucted . Analysis of fluid withdrawn from the " trapped" portion of th e ventricle revealed an ex tr emely eleva ted protein con- tent , co nfirming th e su spected etio logy of the h yperintense appearance on Tl-weighted images. Intr aopera tiv e frozen sections suggested benign fibrous and vascular tissue. Microscopi c examination revealed a mesench yma l-type neopla sm with rich vascularity. No sign ificant mitotic act iv - it y, tumor necrosis, or nu clea r pl eomo rphi sm was found. Special stains demon str ated no glial co mponent. Th e initial diagnosis was angioblastic meningioma because of these findings . However, this tum or lacked the ultrastructural features of meningothelial or arachnoid cap cell s, being composed of collagen-producing fib rob lasts of varying de- grees of maturation without interdigitat in g proc esses or papillary structures seen in ch oro id pl ex us or ependyma l elements. The final diagno sis was benign fibroma with chronic inflammator y c hange and focal dystrophic calc ifi- ca tion. The mass appeared to ari se from the choro id plexus stroma. Following resection , th e patient has undergone clinical examination every 6 month s and is doing well without symptoms or neurol og ic deficit 2 years afte r remova l of the neoplasm . Two po stop erativ e MR scans reveal post- operative c hange with no evi dence of recurr ence . Discussion True intracerebral fibromas are rare neopla sms that may be difficult to differ en tiat e histologi ca lly from meningiomas . Indeed, this neo plasm was inseparable from an angioblastic meningioma by immunohistochemistry and required ultrastruc- tural techniques for the final diagnosis . Th e rarity of intracerebral fibromas is usually attributed to the paucity of connective tissue within the brain . It has been noted that fibroblastic element s within the central nervous system tend to produ ce ma- Received December 30, 1991; revision requ es ted Apr il 9, 1992 ; revision received May 13 and accepted May 27. 1 Department of Radiology and 2 Department of Pathology, Scott[, White Clinic and Memorial Hospital, Texas A0M University College of Medicine, T emp le, TX 76508. 3 Address reprint requests to L. Gi ll Na ul , MD, Depa rt ment of Radiology, Scott[, White Clinic, 240 I South 31st Str ee t, Temple, TX 76508. AJNR 1 4:49 1-492, Mar/ Apr 1993 0195-6 108/ 93 / 1402-0491 © America n Society of Neuroradiology 491