DISCUSSION: The differential diagnosis of mass lesions in the perisellar
region is wide. Pituitary adenoma and craniopharyngioma are the most common,
however, this latter lesion typically shows cystic spaces and often is
calcified. Invasive adenoma or pituitary carcinoma are other possibilities.
Less common primary tumors would include Langerhans cell histiocytosis
(histiocytosis X), lymphoma, myeloma, germinoma, and chordoma. Solitary
metastases in a patient with no known primary malignancy would be distinctly
uncommon, but renal cell carcinoma and melanoma are notorious for occult
primary tumors presenting with metastases. This is by no means a complete list
of potential perisellar masses: over 30 different lesions have been reported
in this region1.
In this case, the histologic features of the tumor strongly suggest a germinoma and this diagnosis is supported by immunohistochemistry for placental alkaline phosphatase.
Germinomas outside of the gonads typically occur in midline structures such as the sacrococcygeal, mediastinal, and retroperitoneal region as well as the pineal gland. Perisellar germinomas most commonly occur in children and arise in the hypothalamic region2 or at the base of the brain, usually in close association with the pituitary stalk and optic nerves. Unlike germinomas of the pineal, which predominantly occur in males, the distribution amoung the sexes is approximately equal when these tumors arise in this location. Diabetes insipidus is the most common presenting symptom with visual symptoms or hypopituitarism developing later. This case is atypical because of the presenting complaint of visual problems. Germinomas confined to the sella are distinctly uncommon. A retrospective review of 108 non-adenomatous sellar tumors evaluated by the neurosurgery department and the University of Hamburg during 1970-1990 reported only one germinoma diagnosed in this region.2 Treatment of germinomas is by radiotherapy and response is favorable with over 85% 10-year survival2.
1. Burger PC, Scheithauer BW, Vogel FS. Surgical Pathology of the Nervous
System and its Coverings (3rd edition). Churchill Livingstone, New York, 1991;
2.Nishio S, Inamura T, Takeshita I, Fukui M, Kamikaseda K. Germ cell tumor in the hypothalamo-neurohypophysial region: clinical features and treatment. Neurosurg Rev 16 (1993):221-226.
3. Sautner D, Saeger W, Ludecke DK. Tumors of the sellar region mimicking pituitary adenomas. Exp Clin Endocrinol 101 (1993):283-289.
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