Endocrine Abstracts

Background: Secondary malignant sarcoma in the sella after radiotherapy for pituitary tumours is rare. Osteogenic sarcoma arising within the fossa after pituitary irradiation has only been described in a few case reports.

Clinical Case: A 31-year-old male patient without significant medical History presented in 2012 with bitemporal hemianopia. There were no associated headaches or clinical features of excess hormone secretion. MRI demonstrated a 26×30×28 mm mass in the pituitary fossay with suprasellar extension and compression of the optic chiasm. There was no invasion of the cavernous sinus. Biochemical investigations showed a mildly elevated serum prolactin of 851 mIU/l (normal range <500), low morning cortisol of 19 nmol/l, low testosterone of 1.8 nmol/l and normal thyroid function- TSH 3.60 mIU/l, free T4 10.4 pmol/l, consistent with a non-functioning pituitary tumour with partial hypopituitarism. He underwent urgent transsphenoidal resection of the tumoury resulting in normalization of vision and a small intrasellar tumour remnant. Three years later repeat surgery was undertaken due to tumour regrowth, now measuring 32×23×30 mm. Histopathological evaluation confirmed a pituitary neuroendocrine tumour of gonadotroph lineage, with expression of SF1 but negative hormonal immunoreactivity. There was no histological invasion or mitoses. Ki-67 was 8%. Because of a significant tumour remnant, he then received postoperative radiotherapy (49.2 G, in 30 fractions). yearly imaging showed stable and asymptomatic residual tumour. 8 years after radiotherapy he experienced worsening visual disturbance and headaches. Repeat MRI showed pituitary mass regrowth to 44×32×44 mm with a large area of unenhanced low T1 and T2 signal intensity and macrocalcification. A third transsphenoidal resection of the recurrent pituitary tumour was undertaken. Histopathology assessment now revealed a gonadotroph tumour seen closely intermingled with a malignant spindle cell component. Focal areas of osteoid production were seen. These cells demonstrated expression of SATB2, loss of H3K27me3 and high Ki67 of 60%. A diagnosis of radiation- induced sarcoma was favoured over sarcomatous transformation in view of the latency period between radiotherapy and the development of this neoplasm in the field of radiation.

Conclusion: This case describes a rare and serious complication of radiotherapy occurring 8 years after treatment of a pituitary gonadotroph tumour, highlighting the need for careful long-term radiological monitoring.