Presentation
Decreased vision.
Patient Data
There is a T1 isointense to brain, T2 hyperintense mass filling the inferior recesses of the third ventricle and extending down along the infundibulum into the pituitary fossa. It demonstrates intermediate relatively homogeneous contrast enhancement. The pineal gland, is a little bulky and demonstrates similar signal intensity and enhancement.
The mass elevates and compresses the optic chiasm and results in increased signal in the optic tracts bilaterally.
The patient went on to have an endoscopic transphenoidal biopsy.
Histology
MICROSCOPIC DESCRIPTION: The sections show fragments of unremarkable anterior pituitary tissue and fragments of loosely aggregated tissue which is densely infiltrated by small lymphoid cells and scattered eosinophils. In several fragments there is also a population of atypical large cells with round, oval and reniform nuclei, some with prominent nucleoli and a variable amount of pale cytoplasm. These cells are intimally mixed with the small lymphoid cells. An occasional mitotic figure is identified in the large cells.
Immunohistochemistry shows strong staining in the atypical large cells for c-kit (CD117) in a membrane and Golgi pattern. Scattered large cells also show moderate staining for CD30 and weak staining for placental alkaline phosphatase (PLAP). The small lymphoid cells are predominantly CD3+ T lymphocytes with lesser numbers of CD20+/CD79a+ B lymphocytes. There is positive S-100 immunostaining in several fragments consistent with background posterior pituitary tissue. No staining for CD1a is seen. No trophoblastic component is identified.
DIAGNOSIS: germinoma
Case Discussion
This case illustrates typical appearances of a germinoma, tracking along the floor of the third ventricle and down the pituitary infundibulum.
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