GIANT CELL-RICH SOLITARY FIBROUS TUMOR
The radiological differential diagnosis favored neurofibroma or schwannoma, the absence of an enhancing dural 'tail' militating against meningioma. Immunohistochemical expression of bcl2, CD34 and CD99, combined with lack of EMA and significant S100 expression, argued against all three prime radiological considerations and was most compatible with the giant-cell rich variant of solitary fibrous tumour (SFT). Despite the bizarre cytology, the lack of mitoses and necrosis was consistent with a benign tumour.
Intracranial SFT generally are rare, fewer than 200 being reported to-date.1,6 As a group, they usually occur in adulthood with equal sex-ratio.3 The majority are intra-cranial and extra-axial but around one fourth are intra-spinal and intra-dural3. Origin from spinal nerves is rare; invasion of parenchyma and nerve roots may occur5 and CSF seedlings are reported.5 Based on one comprehensive review, only 5.8% of CNS SFT exhibited malignant behaviour,3 considerably lower than the 37% reported for pleural SFT.2
The giant-cell rich variant does not receive separate consideration in the 2007 WHO classification of CNS tumors but is a recognized extra-cranially where its behavior has been reported as benign2. The distinction between giant-cell rich SFT and giant cell angiofibroma has been disputed4,7 and the two entities may be regarded as essentially equivalent.
Prognosis of intracranial giant-cell rich SFT is necessarily guarded in view of the paucity of data. However, optimism may be adduced from the generally benign behavior of CNS SFT as a group. The present case, exhibiting sustained clinical improvement after a sub-total resection, would support that view.
Contributed by Kieren S J Allinson, BSc Hons, MB ChB, Angelos G Kolias, MSc, MRCS, Yiannis Philippou, MB, BChir, Diederik O Bulters, BSc, MB, ChB, FRCS (SN), Cyril Fisher MA, BM, BCh, MD, DSc, FRCPath, Hon MRCR, Arie Perry MD, Andrew F Dean, BM, BCh, FRCPath