The anterior pituitary gland is very hypoplastic or atrophic. The epithelial nests in figures 2-4 are meningothelial cells, but I am not sure they are abundant enough to be part of a meningioma. The various tubules are probably Rathke's cleft remnants. I do not see a definite neoplasm. Is it possible that there was a cystic lesion found during surgery? A mystery to me. 

With additional photomicrographs of the lesion uploaded now, this is a case of WHO grade I meningioma in the sellar region and cavernous sinus for sure. Because of internal carotid arteries, optic nerves and many venous sinuses in this location, complete tumor resection is usually not easily achieved. Careful follow-up for recurrence is needed, and gamma knife therapy for localized recurrence will be a good option in the future.