Metastatic lung adenocarcinoma presenting as a pituitary mass

What happened, in summary

A 64-year-old Asian woman was hospitalized after 3 months of blurred vision and intermittent headache. Her vital signs and routine blood and urine tests were unremarkable, but eye examination showed reduced vision, especially in the right eye. Initial brain CT and MRI suggested a pituitary macroadenoma, a usually non-lung diagnosis that can mimic metastatic disease in the sellar region. MRI showed a homogeneously enhancing sellar lesion measuring about 1.6 × 0.8 × 1.3 cm with an hourglass appearance. During the same workup, chest CT found irregular nodules in the basal segment of the left lower lobe measuring 2.0 × 1.7 cm, suspicious for lung cancer. PET/CT showed metabolically active lesions in both the lung and sellar region, raising concern for malignancy. Fiber bronchoscopy identified a left lung neoplasm, and staining suggested lung adenocarcinoma. Postoperative pathology from the sellar mass showed metastatic adenocarcinoma. Immunohistochemistry supported lung origin: CK7, CK18, TTF-1, Napsin A, and GATA3 were positive, while CK20, CDX-2, GFAP, PAX-8, ER, and HER2 were negative. The Ki-67 index was 10%. Next-generation sequencing identified somatic mutations in TSC2, POLD1, ARID1A, CTNNB1, and ERBB2, and PD-L1 expression was low, with a tumor proportion score of 1%. The diagnosis was metastatic lung adenocarcinoma involving the pituitary/sellar region. Systemic lung-cancer treatment, recurrence status, and longer follow-up were not described in the available case details. She had no prior hospitalization or significant personal or family history noted. Routine blood and urine tests were normal, while endocrine findings were recorded separately in the medical table.