Miscellaneous Tumors of the Sellar Region

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In addition to the major forms of sellar and parasellar neoplasia reviewed, a variety of other rare and occasionally exotic tumors periodically involve the sellar region (1) (Table 1). Despite the diversity of tumor types represented, most have a fairly nonspecific clinical profile, characterized by a radiologically evident sellar/parasellar mass in association with visual dysfunction, low-grade hyperprolactinemia, and/or varying hypopituitarism. Given their rarity, these tumors are seldom considered in the preoperative differential diagnosis, because most are managed as if they were seemingly ordinary endocrinologically inactive pituitary adenomas. With their true identity being revealed only after pathologic examination of the surgical specimen, their diagnosis often arrives as something of a surprise.

Schwannomas

Nerve sheath tumors, although accounting for almost 10% of all intracranial tumors, rarely occur in the sellar and parasellar regions. In fact, only six such cases have been reported to date, with four arising from within the sella proper showing suprasellar extension, one arising from the tuberculum sellae with suprasellar extension, and one originating from the extracavernous trigeminal nerve, which also extended into the suprasellar space (81-84). Schwannomas that do not arise from a cranial nerve, such as those of intrasellar origin, are presumed to arise from ectopic Schwann cell rests or from autonomic vasomotor fibers. With the evolution of cavernous sinus surgery, schwannomas arising from cranial nerves within the cavernous sinus are increasingly recognized and surgically managed. In a recent review by Sekhar et al. 12% of 103 benign cavernous sinus tumors were schwannomas (85).

Paragangliomas

Paragangliomas are tumors of neural crest origin, the majority of which arise in the adrenal medulla and paraganglia. More than 80% of extra-adrenal cases involve the head and neck, with the carotid body, temporal bone, and vagal body being the classic and most common sites. Though rare, there have been periodic reports of paragangliomas arising in the parasellar region (86-92). Some have a primary intrasellar origin, whereas others have arisen in the cavernous sinus and secondarily involving the sella. Headache, hypopituitarism, and diplopia were variably present, with a sizeable sellar region mass being a uniform finding. Some are amenable to transsphenoidal removal, whereas others have been treated transcranially. Three of these cases were treated with postoperative radiation therapy. Given that neither the pituitary gland nor adjacent parasellar structures contain paraganglionic tissue, the cellular origins of these tumors is obscure. Persistent embryonic "rests" of paraganglionic tissue and/or abnormal migration of neural crest cells into the parasellar region have been invoked as possible mechanisms accounting for their origin in or around the sella.

Hemangioblastomas

Isolated accounts of sellar region hemangioblastomas, both sporadic and in association with the von Hippel-Lindau (VHL) syndrome, have appeared in the literature (93). Of reported examples in the sellar region, most originated from the anterior pituitary, pituitary stalk, optic nerves, and upper clivus (94-96). The treatment is surgical resection with a goal of gross total resection. In all seemingly sporadic cases, one must undertake investigations to exclude an underlying VHL syndrome.

Lipomas

Rarely, incidental lipomas of the hypothalamus are seen at autopsy, appearing as discrete pedunculated masses hanging down from the tuber cinereum. Genuine symptomatic examples are exceptional and are not only more adherent to but also have parenchymal involvement with the hypothalamus, tuber cinereum, and mammillary bodies (97,98). Depending on their size, hypothalamic dysfunction, hyperprolactinemia, and varying degrees of hypopituitarism may all be presenting features. Although benign and slow growing, symptomatic lipomas are often so intimately related to surrounding nervous tissue that complete resection is seldom possible.

Other Tumors

An additional spectrum of rare and peculiar tumors of the parasellar region are the subjects of isolated case reports. These include fibrosarcoma (99), gloman-gioma (100), cavernous hemangioma (93,101-103), primary lymphoma (104), primary melanoma (105,106), myxoma (107), osteogenic sarcoma (108), and pseudotumor (109).

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