Inflammatory pseudotumor of the skull base involving fissura petrooccipitalis: a rare case with challenging diagnosis.

Inflammatory pseudotumor (IPT) is a benign entity that may present as a solid mass mimicking a malignant neoplasm. Histologically, they are composed of varying proportions of myofibroblastic spindle cells, lymphocytes, and plasma cells. Skull base IPT is rare and usually occurs in adults with no sex predilection. The skull base IPT typically presents with headache, and/or cranial nerve palsy. There is no consensus regarding treatment of skull base IPT due to its rarity. Surgical resection and corticosteroid therapy have generally been used. The preoperative diagnosis of skull base IPT is usually difficult due to its nonspecific clinical and radiologic features. We report a case of a 42-year-old woman with IPT originating from the skull base. To our knowledge, this is the first case of IPT invading fissura petrooccipitalis. When a mass in the skull base appears hypointense on T2-weighted imaging with aggressive growth and bony destruction, IPT should be considered in the differential diagnosis.