Melanoma metastasis to a nonfunctioning pituitary macroadenoma: illustrative case

Abstract

BACKGROUND Metastases to the central nervous system are often multiple in number and typically favor the gray-white matter junction. Collision tumors, defined as the coexistence of two morphologically different tumors, such as metastases to a known pituitary adenoma (PA), are exceedingly rare. Only a few reported cases of metastases to a PA exist in the literature. OBSERVATIONS The authors present the case of a 64-year-old man with a known history of stage IV metastatic melanoma who was found to have hypermetabolic activity in the sellar region on surveillance positron emission tomography. On laboratory evaluation, he had clear evidence of pituitary axis dysfunction without diabetes insipidus. Subsequent magnetic resonance imaging showed a 2.4-cm sellar mass with features of a pituitary macroadenoma and internal hemorrhage, although no clinical symptoms of apoplexy were noted. He underwent a transsphenoidal endoscopic endonasal approach for resection of the sellar lesion. Final pathology showed a collision tumor with melanoma cells intermixed with PA cells. LESSONS Histological analysis verified the rare presence of a collision tumor of a melanoma metastasis to a nonfunctional pituitary macroadenoma. Metastasis to a preexisting PA, although rare, should be considered in the differential diagnosis in patients with sellar lesions and a known cancer history.

Collision of Two Tumors: A Case Report of a Lung Adenocarcinoma With Metastasis to a Pituitary Adenoma

“…1 Among collision tumors that involve carcinoma metastasizing to sellar tumors, the reported recipient tumors include pituitary adenomas, meningiomas, gliomas, schwannomas and hemangioblastomas, with meningiomas being a more common type of sellar recipient tumor than pituitary adenomas. 1,2 Although pituitary adenomas are the most common sellar lesions comprising 10 to 15% of In addition to the high incidence of visual disturbances and hypopituitarism, central diabetes insipidus is the most common symptom in patients with pituitary metastasis due to the predilection for hematogenous metastatic spread to the posterior pituitary lobe via the neurohypophyseal vessels. 6 Up to 30% of patients with pituitary metastases present with CDI, which rarely occurs with pituitary adenoma alone, as pituitary adenomas typically arise from neoplastic metastatic growth within a pre-existing, benign pituitary adenoma.…”

“… 1 Among collision tumors that involve carcinoma meta-stasizing to sellar tumors, the reported recipient tumors include pituitary adenomas, meningiomas, gliomas, schwannomas and hemangioblastomas, with meningiomas being a more common type of sellar recipient tumor than pituitary adenomas. 1 , 2 Although pituitary adenomas are the most common sellar lesions comprising 10 to 15% of all intracranial tumors, metastasis to a pituitary adenoma occurs in only 1 to 5% of patients with malignancies. 1 In the 36 reported cases of pituitary adenoma with metastatic carcinoma (including our case), lung cancer was the most common primary malignancy (n=9), with the majority being non-small cell lung carcinoma.…”

“… 6 Up to 30% of patients with pituitary metastases present with CDI, which rarely occurs with pituitary adenoma alone, as pituitary adenomas typically arise from the anterior lobe of the gland, which receives systemic arterial blood supply mainly from the capsular and inferior hypophyseal arteries. 2 , 7 Metastasis to a pituitary adenoma can rarely occur either via the arterial supply of the adenoma itself, via direct extension of an adjacent bone metastasis or via meningeal spread through the suprasellar cistern. 1 Hence, the presence of CDI in our patient should dissuade the diagnosis of pituitary adenoma as the sole cause of the sellar mass.…”

“…1,3,4 Other primary malignancy sites reported in these case series were the kidney (n=5), breast (n=5), melanoma (n=4), colorectum (n=3), stomach (n=1), pancreas (n=1), mediastinum (n=1) and prostate (n=1); the remaining 5 cases had unknown primary sites. [1][2][3][4] With the majority of the reported recipient pituitary tumors as non-functioning pituitary adenomas, most of the patients presented with symptoms of mass effect such as headache, cranial nerve palsies, visual disturbances and anterior pituitary hormone deficiency. 3,4 Compression of the pituitary stalk disrupts delivery of dopamine, the major inhibitory regulator of prolactin secretion, to the pituitary gland.…”

“… 1 Tumor-to-tumor metastasis, also known as a collision tumor, involving metastasis to a pituitary adenoma is rare, with only 35 cases being reported in literature to date. 2 The definitive diagnosis of a collision tumor is determined by histopathological examination, but the clinical presentation, a history of malignancy and imaging findings may provide clues to support the diagnosis. We present a rare case of a lung adenocarcinoma with metastasis to a non-functioning pituitary adenoma, diagnosed after post-operative histopathological and immunohistochemical examination of the excised tissue.…”