Case Presentation: A 70-year-old man with a past medical history of HIV on antiretroviral therapy, chronic obstructive pulmonary disease, tobacco use disorder, and ischemic cardiomyopathy presented due to 2 weeks of headache and hemoptysis. On review of systems he noted chronic diplopia going on for the last few months. The initial examination did not note the presence of a cranial nerve palsy. Initial work up in the emergency department included a CT angiogram of the thorax that revealed a new right lower lobe mass, concerning for malignancy. CT head was notable for a new right sided hyperdense lesion within the cerebellum. MRI of the brain revealed bilateral cerebellar lesions concerning for hemorrhagic metastasis. During the initial workup he was hemodynamically stable with normal blood pressure and normal basic laboratory values. A rapid response was called following his lung biopsy due to hypotension which was poorly responsive to IV fluids and required the initiation of midodrine. Lactic acid levels remained normal and infectious workup was negative. Cortisol and adrenocorticotropic hormone levels obtained the following morning were low, (ACTH < 3, AM cortisol 2.1) indicative of secondary adrenal insufficiency. MRI of the pituitary gland revealed a two-centimeter lesion within the pituitary, encroaching upon the cavernous sinus which was not seen on the initial MRI brain. Further evaluation revealed panhypopituitarism (TSH < 0.03, Free T4 0.5, FSH < 1, and LH < 1) and a right cranial nerve VI palsy. He was started on hydrocortisone and levothyroxine for adrenal insufficiency and hypothyroidism related to panhypopituitarism. Biopsy results from his lung mass were consistent with poorly differentiated lung adenocarcinoma.
Discussion: Lung adenocarcinoma has the potential to metastasize, most commonly to the bones, the liver, and the cerebellum. In this case, the patient’s initial chief complaints led to the identification of the lung mass and cerebellar metastasis. We suspect that the lung biopsy, NPO status, and associated anesthesia precipitated adrenal crisis, leading to the eventual diagnosis of the pituitary mass. It is rare for lung adenocarcinoma to metastasize to the pituitary gland. However, the chronic diplopia reported on admission may have lead to an earlier diagnosis if not for reliance on the initial CT and MRI findings. MRI of the whole brain compared to MRI of the pituitary gland share very close specificity levels (80-90% and 100%, respectively) in detecting pituitary lesions; however, the sensitivity of MRI of the brain compared to MRI of the pituitary, are significantly different (30-35% and 90-95%, respectively) (Ji Ye Lee et al. 2017).
Conclusions: Lung adenocarcinoma with metastasis to the pituitary is exceedingly rare. The presence of diplopia on review of systems was an early clue to the diagnosis but was dismissed given discordant MRI and CT findings. A thorough physical examination on admission would have revealed a cranial nerve six palsy, which is often associated with pituitary masses due to impingement on the cavernous sinus. Additionally, the lack of pituitary involvement on MRI brain should not have been reassuring given the lack of sensitivity the imaging provides for smaller pituitary lesions. Luckly, the patient’s adrenal crisis was promptly recognized and his panhypopituitarism was appropriately treated. When pituitary lesions are suspected, obtaining dedicated pituitary imaging is critical as a standard MRI brain lacks the sensitivity of dedicated pituitary imaging.