Granular cell tumour of the neurohypophysis: an unusual cause of hypopituitarism

Abstract

Granular cell tumours (GCT) are rare, slow-growing, benign neoplasms that are usually located in the head and neck. They are more frequent in the female gender and typically have an asymptomatic clinical course, being diagnosed only at autopsy. Symptomatic GCT of the neurohypophysis are exceedingly rare, being less than 70 cases described so far. The authors report on a case of a 28-year-old male that presented to the Endocrinology clinic with clinical and biochemical evidence of hypogonadism. He also reported minor headaches without any major visual symptoms. Further laboratory tests confirmed hypopituitarism (hypogonadotrophic hypogonadism, central hypothyroidism and hypocortisolism) and central nervous system imaging revealed a pituitary macroadenoma. The patient underwent transcranial pituitary adenoma resection and the pathology report described a GCT of the neurohypophysis with low mitotic index. The reported case is noteworthy for the rarity of the clinicopathological entity.

Learning points: Symptomatic GCTs are rare CNS tumours whose cell of origin is not well defined that usually give rise to visual symptoms, headache and endocrine dysfunction.Imaging is quite unspecific and diagnosis is difficult to establish preoperatively.Surgical excision is challenging due to lesion's high vascularity and propensity to adhere to adjacent structures.The reported case is noteworthy for the rarity of the clinicopathological entity.

Figure 1

Large suprasellar mass extending caudally to the sella turcica with 29 × 27 × 35 mm compressing the pituitary gland and optic chiasm. The lesion was isointense on T1 (panels 1 and 2) and hypointense on T2-weighted imaging (Panels 3 and 4). It is responsible for the enlargement of the sella turcica, marked compression of the infundibulum, optic chiasm, third ventricle pavement (causing ventricular deformation) and right cerebral peduncle.

Figure 2

(A) Hematoxylin and eosin, 200×; Highly cellular neoplasm, composed of nests of fusiform and polygonal cells with abundant eosinophilic cytoplasm. The nuclei are small, round and monotonous, without mitotic figures. Several large vessels can be appreciated. (B) Hematoxylin and eosin, 400×; In higher magnification, a nest of cells showing granular cytoplasm and eccentrically located nuclei. (C) Periodic acid-Schiff diastase, 400×; Cytoplasmic granules are PAS-D positive, revealing that the granular is not due to accumulation of glycogen. (D) S100, 100×; Immunohistochemistry for S100 was positive.

Figure 3

Electron microscopy (performed in PEFF tissue). Numerous vesicular structures account for the cytoplasmic granularity. The vesicular structures consist of secondary lysosomes.

Figure 4

Current tumour status, measuring 37 × 32 × 26 mm, isodense in T1 and T2 with intense homogeneous contrast enhancement.