AN UNUSUAL DIFFUSE CD34 STAINING IN AN OLFRACTORY GROOVE CELLULAR SCHWANNOMA: CASE REPORT.

Background: Intracranial schwannomas are benign lesions, expected to exhibit characteristic ultrastructural features and immunophenotypic profile, typically being S-100, SOX10 and collagen-IV positive, while other markers, including CD34, are not usually expressed and are employed in the diagnostic elimination process. Case presentation: A 51-year-old female presented with a rapidly deteriorating neurological status. MRI showed a heterogeneous enhancing neoplasm of the anterior fossa. Preoperative differential diagnosis predilected an esthesioneuroblastoma. A bifrontal craniotomy with total excision of the lesion was performed. Dural infiltration was present. There was no association with the olfactory system. Microscopic examination revealed a uniform population of spindled to slightly epithelioid cellular proliferation with no significant atypia, low mitotic activity, and foci of necrosis. Upon immunohistochemical investigation the tumor was consistent with cellular schwannoma. Diffuse positivity for CD34 was an unusual finding. Discussion: Cellular schwannoma should be considered in the presence of an anterior fossa tumefaction. Olfactory nerve is not directly associated with these lesions. Various theories have been proposed, with the meningeal trigeminal branches' origin being the most probable. The characteristic ultrastructural Antoni formations may be scarce or even absent in cellular schwannomas creating potential diagnostic difficulties. Unusual diffuse CD34 positivity should not be employed for excluding the diagnosis. [ABSTRACT FROM AUTHOR]

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