Abstract
Background. The EML4-ALK (echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase) fusion gene is an oncogenic driver mutation observed in patients with non-small cell lung cancer (NSCLC). Crizotinib has been shown to be effective in treating EML4-ALK-rearranged NSCLC detected using fluorescence in situ hybridization (FISH). Case. A 54-year-old male was diagnosed with adenocarcinoma of the lungs. We evaluated the presence of the EML4-ALK fusion gene in two specimens, a pretherapeutic specimen and a specimen obtained after the subsequent administration of third-line chemotherapy. The results of both examinations were positive on ALK immunohistochemistry but indeterminate on EML4-ALK FISH. However, treatment with crizotinib was effective. The incidence of indeterminate EML4-ALK FISH results at our hospital is 13 of 23 samples (57%). In our facility, mercurochrome is used to mark the tissue prior to embedding, and, because mercurochrome has a fluorescent green color, this makes it difficult to assess the results of specimens examined using EML4-ALK FISH. Conclusions. In order to correctly diagnose EML4-ALK-rearranged NSCLC, it is essential to appropriately store and identify effective means of processing tissue specimens to accurately detect the ALK fusion gene.
