A case of invasive mucinous adenocarcinoma of the lung showing stepwise progression at the primary site

Abstract Objective Invasive mucinous adenocarcinoma (IMA) is a variant of lung adenocarcinoma. We present one case of IMA with mixed mucinous and non-mucinous components, suggesting stepwise progression within the tumor. Material and method The two different components of IMA were separately examined by immunohistochemistry and performed amplicon sequencing (Ion Ampliseq Cancer Hotspot Panel v2, ilumina, San Diego, CA). Result Macroscopically, the IMA contained a small and well demarcated solid part. Tumor cells in the main part showed abundant intracytoplasmic mucin, whereas those in the solid part showed scant intracytoplasmic mucin and high-grade nuclear atypia. Both parts harbored the same KRAS p.G12 V mutation. The amplicon sequencing of the IMA showed oncogenic TP53 p.P278 L mutation was detected only in the solid part. Conclusion Oncogenetic TP53 mutation might promote stepwise progression of this case of IMA.