Non-small-cell lung cancer infiltrated with chronic myelomonocytic leukaemia: a molecular diagnostic challenge to recognise mixed cancers in a single biopsy

Molecular profiling techniques such as targeted next-generation sequencing (NGS) have become increasingly important in routine cancer diagnostics. Genomic alterations that are characteristic in certain malignancies are sometimes also detected in other cancers. Detection of rare variants may challenge the initial diagnosis or uncover a co-existing malignancy.1,2 We report on a non-small cell lung cancer (NSCLC) case with an oncogenic mutation in PIK3CA, and unusual mutations in both MET and IDH2, of which the last was shown to originate from tumor-infiltrating chronic myelomonocytic leukemia (CMML).