Hepatitis is one of the serious immune-related adverse events (irAEs). However, delayed-onset hepatitis induced by immune-checkpoint inhibitors (ICIs) is rare, and the histopathological features remain to be clarified. A 65-year-old woman with advanced lung adenocarcinoma in the right upper lobe (cT4N3M1c, c-stage IVB) received four courses of pembrolizumab. Her hepatic and biliary tract enzyme levels started increasing 2 months after the final administration of pembrolizumab, and the elevated levels of these enzymes prolonged. Liver biopsy revealed panlobular infiltration of inflammatory cells, and most of the infiltrating inflammatory cells were lymphocytes; however, there were a small number of neutrophils, eosinophils, and plasma cells. There was no confluent necrosis. Furthermore, immunohistochemical analyses proved that infiltrating lymphocytes were predominantly CD3-positive (CD3+) and CD8+, and few CD20+ and CD4+ lymphocytes were observed. Based on these findings, she was diagnosed with a case of hepatitis as an irAE. Administration of prednisolone (0.5 mg/kg/day) as well as the addition of azathioprine failed to suppress the deterioration. However, an increase in the dose of prednisolone (up to 1 mg/kg/day) enabled us to control hepatitis. This case showed that hepatitis can occur even after discontinuation of ICIs, and that liver biopsy may be useful in the diagnosis. Clinicians should not hesitate to perform liver biopsy for confirmation of the diagnosis.

Encephalitis is very rare, but often fatal immune-related adverse event (irAE) of immune checkpoint inhibitors (ICIs). A 65-year-old Japanese woman was admitted to our hospital because of general fatigue, chillness and high-grade fever for 4 days, 8 months after the initiation of the first-line pembrolizumab monotherapy for metastatic pulmonary adenocarcinoma. On the hospital day 3, she suddenly presented delirium and uncontrollable impaired consciousness. Although the magnetic resonance imaging (MRI) did not suggest a diagnosis of encephalitis and meningitis, the spinal fluid showed abnormally elevated levels of protein (317.6 mg/L) and cell count (197 cells/µL) with increased mononuclear cells (93%). An empirical and intravenous administration of acyclovir in doses of 10 mg/kg body weight every 8 h and steroid pulse therapy in dose of 1 g/body/day from the hospital day 5 until her death failed to improve her conditions. She died on the hospital day 8. The postmortem autopsy showed viable cancer cells in the metastatic tumor in the left occipital lobe and in the spinal fluids. However, many inflammatory cells infiltration in the meninges and perivascular cuffing were prominent especially in the brain stem and medial part of the temporal lobe. Infiltrating lymphocytes in the meninges and parenchyma of the brain stem were mainly composed of cluster of differentiation (CD)8-positive lymphocytes. For irAE encephalitis, early recognition of early signs and symptoms and subsequent early therapeutic intervention are necessary. It is important for oncologists to keep in mind of the possible adverse effects of immunotherapies on the nervous system.

Uncommon epidermal growth factor receptor (EGFR) gene mutations include G719S, T790M and S768I. T790M gatekeeper mutation is the most frequent mechanism of acquired drug resistance to first- and second-generation EGFR-tyrosine kinase inhibitors (TKIs). Osimertinib is a specific EGFR-TKI to overcome T790M resistance mutation. However, owing to a new drug and a rare mutation type, it remains unknown whether osimertinib is effective for acquired S768I. Herein, we reported a 76 year-old woman with pulmonary adenocarcinoma, which had acquired EGFR mutations of S768I and T790M in addition to original G719S after long gefitinib treatment. These mutations were detected in biopsy specimen of liver metastases. During two months of osimertinib, multiple liver metastases progressively enlarged. This case suggested that acquired S768I mutation might be resistant to osimeritinib, despite of co-occurrence of T790M.