gms | German Medical Science

Objective: Although malignant melanoma frequently metastasizes into the brain, pituitary melanoma is rare. We report an uncommon case of pituitary and lung metastatic melanoma and deliver a brief review of the literature on primary and metastatic pituitary melanoma.

Methods: An 81-year old female presented to our emergency room with a 1-week history of progressive horizontal diplopia. She denied further symptoms and any history of cancer. Except of left abducens palsy, neurological examination was normal. Magnetic resonance imaging demonstrated a multinodular pituitary mass with heterogenous contrast enhancement. Considering an endocrine-inactive pituitary adenoma, transsphenoidal resection was performed. Postoperatively, the initial symptoms recovered fully. Histological examination revealed a pituitary malignant melanoma. We performed a literature search on PubMed using the keywords “pituitary”, “metastatic”, “primary” and “melanoma”.

Results: As no history of melanoma was known, staging workup was performed revealing multiple pulmonary lesions. However, there was no evidence of cutaneous, uveal or gastrointestinal melanoma as a primary tumor. Refusing adjuvant brain radiation and further oncological treatment, the patient died 5 months after surgery. Six reports of metastatic and seven reports of primary pituitary melanoma were analyzed. Next to diplopia due to cranial nerves III, IV and VI palsy, diabetes insipidus, headache and visual disturbance were common symptoms at first presentation. In metastatic pituitary melanoma, symptoms tend to progress more rapidly than in primary pituitary melanoma. Due to its melanin content, pituitary melanoma showed a high intensity on T1-weighted images. In contrast, pituitary adenoma is generally T1-hypointense. Transsphenoidal resection often resulted in immediate relief of symptoms. Normally, adjuvant irradiation of the sellar region was performed.

Conclusion: Since pituitary melanoma is rare, it may be misinterpreted as endocrine-inactive adenoma. Occasionally, pituitary melanoma could be identified preoperatively by characteristic appearance of melanin in MRI tomography. Transsphenoidal resection relieves symptoms and prognosis is dependent on overall tumor stage and local tumor control.