Endocrine Abstracts

Introduction: We submit a rare presentation of round blue cell pituitary tumour complicated by cranial diabetes insipidus following transphenoidal surgery.

Case history: 47-year-old lady with severe headache was diagnosed with a 10 mm non functioning pituitary macro adenoma. Initial plan for conservative management was revised as she developed sixth cranial nerve palsy, bi temporal hemianopia and rapidly enlarging pituitary tumour to 20×18×19 mm. Urgent Transphenoidal pituitary decompression was performed. However the headache got worse and the cranial nerve palsy did not resolve. As the vision significantly deteriorated, she underwent a repeat surgery in 2 weeks. Pituitary tumour was found to be of fibrous consistency and the histology confirmed poorly differentiated round blue cell tumour with mitotic index 50%, positive for CD99 and CD56, cytogenetically unclassified.

Management and discussion: On 1st post-operative day, she developed polyuria and polydipsia, diagnosed with cranial DI and commenced on DDAVP. Next day she developed generalised seizure caused by rapidly developing hyponatraemia, managed with strict fluid balance and a fluid restriction of 1.5l daily with dynamic management DDAVP dose. Chemotherapy with Vincristine, Doxorubicine, Cyclophosphomide and high dose of Dexamethasone started. She developed steroid-induced diabetes mellitus, managed with Glargine. She became very thirsty despite normal serum sodium and urine osmolality raising the possibility of hypothalamic thirst centre being affected by the aggressive pituitary tumour. Patient had some improvement in her vision after two cycles of chemotherapy and it was planned to complete 4 cycles followed by high dose radical adjuvant radiotherapy with an optic chiasm sparing regime. Overall prognosis remains poor.

Conclusion: We presented this case to illustrate a rare, aggressive pituitary malignancy which possibly has invaded the hypothalamus causing disruption to the thirst mechanism in addition to cranial diabetes insipidus.