Case 529 -- A 61-year-old man with hyponatremia

Contributed by Christian Bernreuther, Jörg Flitsch*, Dieter K. Lüdecke*, Christian Hagel
Departments of Neuropathology and * Neurosurgery
University Medical Center Hamburg-Eppendorf, Martinistr. 52, D-20246 Hamburg, Germany


A 61-year old male presented with dizziness, nausea, vomiting, hyponatremia of 128 mmol/l, and a reduced serum osmolality of 271 mosm/kg (normal range 280-300 mosm/kg). A CT scan of the head showed an intra- and suprasellar mass. Endocrinologically, low levels of ADH, 1.2 ng/l (2-6ng/l), morning cortisol, 90 µg/l (100-250µg/l), and testosterone, 1.6 µg/l (2.8-8µg/l). Low-normal values for ACTH, LH, and FSH were also found. Basal hormone levels were normal for PRL, STH, TSH, and IGF-1. After adequate cortisol substitution, the hyponatremia resolved with a complete clinical relief of symptoms. A MRI scan of the sellar region was performed. The scan confirmed an adenoma-like appearance of an intra- and suprasellar tumor of 2.8 x 2.8 x 2.3 cm in diameter without obvious infiltration of the cavernous sinus (Figure 1A and 1B). The optic chiasm was elevated, but an ophthalmological exam showed no signs of chiasm syndrome. No involvement of other cranial nerves was observed. The patient underwent transsphenoidal microsurgery without complications under adapted perioperative hydrocortisone substitution. The post-operative course was uneventful, further anterior lobe insufficiencies or Diabetes insipidus did not occur. A MRI scan 5 months after surgery showed gross total removal of the lesion, however, a suspected remnant of the lesion is currently under observation. (Figure 1C and 1D)


Histological investigation of the specimen revealed a tumor composed of elongated, densely packed, cytologically monotonous cells with fusiform, tapered, and cigar-shaped nuclei growing in haphazardly distributed fascicles. The cellularity was uniform throughout the tissue fragments, hypocellular areas were not found. Occasionally, palisading of nuclei was observed (Fig. 2A). There was no prominent nuclear polymorphism. Mitotic activity was inconspicuous. Intratumoral vessels showed prominent wall thickening with occasional small perivascular hemorrhages. Immunohistochemical studies showed a diffuse positivity for S-100 protein (Fig. 2B) and focal expression of the glial fibrillary-acidic protein (Fig. 2D). There was no significant proliferation, less than 1% of the tumor cells were labelled with Ki-67 antibodies (Fig. 2C). The tumor cells were negative for EMA, cytokeratin, and pituitary hormones.


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