Endocrine Abstracts (2004) 7 P259

Diagnostic difficulty in differentiating between meningioma and pituitary adenoma

ECI Hatfield1, DH Lewis1, M Powell2, KL Ng1, C Kong1 & C Johnston1

1Department of Endocrinology and Diabetes, Hemel Hempstead General Hospital, Hemel Hempstead, UK; 2Department of Neurosurgery, The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.

We report two patients (AB 41 years, LS 55 years) presenting with symptoms of hyperprolactinaemia. Prolactin levels were moderately elevated: 1539 (AB), 1186 (LS) (NR 59-619 mU/L). The remainder of the pituitary profile was normal. Neither patient had visual field defects. MRIs (without contrast) reported pituitary macroadenoma with suprasellar extension but no optic chiasm compression. The initial diagnosis was of probable non-functioning adenoma causing stalk compression. Both patients responded to treatment with dopamine agonists. Follow up MRIs (without contrast) revealed no significant change in tumour size over the next two to four years.However, following contrast MRI, the diagnoses were revised to that of meningioma (plus possible additional pituitary adenoma in LS). Neurosurgical review determined that neither tumour was resectable. Both patients remain well and are regularly reviewed with MRI and visual field assessment.These cases illustrate that difficulties can arise in differentiating between pituitary adenoma and sellar/parasellar meningioma. Meningioma mimicking pituitary adenoma has previously been reported. In addition, meningioma and pituitary adenoma may co-exist, as is the possibility in LS.Several features on contrast MRI can help differentiate between meningioma and pituitary adenoma, such as intensity and homogeneity of enhancement. Furthermore, CT head may aid the diagnosis of meningioma by revealing certain characteristic features, such as hyperostosis.Differentiation between meningioma and pituitary adenoma is important, especially when surgical intervention is a consideration, since the surgical approach will be different in the different tumours.Conclusion:The differential diagnosis of patients with hyperprolactinaemia and a significant sellar mass should include meningioma. Some centres do not perform contrast enhanced MRI for all pituitary imaging. Whilst contrast may not always be required, it is indicated in all those presenting with apparent macroadenoma, as our cases demonstrate. Management of such cases should involve close liaison between neuroradiologist, endocrinologist and neurosurgeon.

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