Metastasis of lung adenocarcinoma within a pituitaryneuroendocrine tumor: case report and review of the literature

Abstract Introduction: Collision tumors in which malignant neoplasms metastasize to pituitary neuroendocrine tumors (PitNETs) are extremely rare. We report a case of PitNET with a history of colorectal and bladder cancers and a relatively rapid progression of neurological symptoms.Case Report: A 75-year-old man who underwent tumor resection for bladder cancer 36 years before and for colon cancer 18 years before without recurrence suffered from right-sided homonymous hemianopsia, ptosis and diplopia of the right eye. MRI revealed a tumor with a diameter of 3.2 cm, extending from the anterior pituitary gland to the suprasellar region. Gadolinium-enhanced MRI of the tumor showed heterogeneous contrast enhancement. Semi-emergency endoscopic endonasal transsphenoidal surgery was performed because of the relatively rapid progression of neurological symptoms. Histopathological examination revealed a group of thyroid transcription factor-1- and napsin A-positive papillary proliferating cells intermingled with α-subunit (α-SU)- and steroidogenic factor-1-positive PitNET cells. The patient was diagnosed with metastasis of lung adenocarcinoma within a PitNET (gonadotroph PitNET).Results: Genetic testing revealed a positive EGFR (Ex-19del) mutation, and chemotherapy was initiated. Additional stereotactic radiotherapy was performed for the residual tumor in the sella turcica. Chemotherapy was continued, and 24 months later, both the primary and metastatic tumors were well controlled.Conclusion: Cases of metastasis of a malignant neoplasm within a PitNET are difficult to diagnose. In the case of a sella turcica tumor with relatively rapid progression of neurological symptoms, early surgical intervention is recommended because of the possibility of a highly proliferative tumor and to obtain pathologic specimens.