Endocrine Abstracts

Introduction: Giant prolactinomas are rare tumors accounting for 2–16% of all prolactinomas. They may be aggressive and invasive. Rarely, they might not have a suprasellar component and grow downward. Such extension can make it difficult to distinguish pituitary adenoma from other skull base tumors. We present a case that was considered to be chordoma based on clinical and radiological imaging features, but was diagnosed as prolactinoma by pituitary biopsy.

Case: A 67-year-old male patient with headache, dizziness admitted to the emergency department. There was no pathological finding in his physical examination. Cranial MRI demonstrated a large mass (5 x 3 x 3.5 cm) which destroyed the clivus, extending anteriorly towards the sphenoid sinus, and surrounding both cavernous sinuse. He was referred to neurosurgery department and underwent transsphenoidal biopsy for the differential diagnosis of clival tumors such as chordoma. The histopathological examination revealed it to be pituitary adenoma and immunohistochemical study showed a strong positive staining for the prolactin. He was diagnosed with giant prolactinoma and referred to our outpatient clinic. He reported reduced libido and difficulties in erection. Visual field examination was normal. Hormonal evaluation revealed that serum prolactin level was significantly increased (6290 ng/ml) and serum IGF-1 level was compatible with age and sex. Serum total testosterone level was decreased (115 ng/dl) while FSH and LH levels were within the reference ranges. The pituitary-adrenal and pituitary-thyroid axis were intact. He was started a dose of cabergoline 500 micrograms once weekly. Then the dose increased to 500 micrograms twice weekly as tolerated. He responded well to the medical treatment. Serum prolactin levels dramatically decreased. Pituitary MRI in 12 weeks intervals showed a remarkable reduction in mass.

Conclusion: This case highlights the importance of including invasive pituitary macroadenomas with infrasellar extension in the differential diagnosis of skull base tumors. Initially, evaluation of clinical signs and hormonal tests in patients with sellar-parasellar masses, can prevent unnecessary invasive procedures.