Atypical presentation of sinonasal cellular schwannoma: a nonsolitary mass with osseous, orbital, and intracranial invasion.

Objective Sinonasal cellular schwannoma represents < 4% of head and neck schwannomas. These benign tumors are typically confined to the nasal cavity or ethmoid sinus. We describe an atypical case of sinonasal cellular schwannoma with diffuse paranasal sinus involvement and both intraorbital and intracranial extension. Results A 62-year-old woman presented with a 6-month history of right orbital proptosis and right-sided headache. Subsequent imaging revealed an invasive paranasal sinus mass extending through the skull base and displacing the right orbit. Preoperative biopsies were not diagnostic but revealed a spindle cell lesion suspicious for malignancy based on lack of encapsulation, infiltration of the sinonasal submucosa, and osseous invasion. The patient underwent open skull base surgery, and pathology confirmed a S100-positive nonencapsulated cellular schwannoma. Conclusion An atypical case of sinonasal cellular schwannoma with intracranial extension is reported. Its presentation is contrary to the common view that these are isolated solitary lesions of the nasoethmoid region. We suggest that sinonasal cellular schwannoma be considered in the differential diagnosis of a poorly defined invasive paranasal sinus mass, particularly following biopsy.

Evidence for the involvement of CYP1A2 in the metabolism of bromodichloromethane in rat liver.

Bromodichloromethane (BDCM) is a drinking water disinfectant by-product that has been implicated in liver, kidney and intestinal cancers in rodents and in intestinal tumors and low birth weight effects in humans. BDCM is also hepatotoxic and requires metabolic activation for both toxicity and carcinogenicity. We have recently reported that CYP1A2 may participate in that metabolism and we now report experiments to support that implication. Induction of CYP1A2 in male F344 rats without inducing CYP2E1 or CYP2B1/2, using TCDD, increased the hepatotoxicity of BDCM when compared to earlier work conducted under similar protocols. Inhibition of CYP1A2, with isosafrole, reduced the metabolism and toxicity of BDCM in the previously induced rats. In addition, specific activities and Western blots for these CYP isoenzymes were measured 24 h after exposure. Activity data show that only CYP1A2 was inhibited by isosafrole; isosafrole forms a complex with CYP1A2 that persists for more than 24 h. Western blot results generally agree with the activity data except that isosafrole induced the protein for all isoenzymes measured. A physiologically based pharmacokinetic model, developed previously, estimated that BDCM metabolism was complete about 7 h after gavage dosing. It is noteworthy that the reduction in CYP1A2 activity was still measurable despite the production of additional CYP1A2 protein during the period of approximately 18 h after BDCM metabolism was complete. These results demonstrate that CYP1A2 does metabolize BDCM and does contribute to hepatotoxicity under certain conditions.