ALK expressed in a gastrointestinal stromal tumor harboring PDGFRA p. D842V mutation:a case report

Gastrointestinal stromal tumors (GISTs) are the most common type of adult mesenchymal neoplasms. The events that drive GIST oncogenesis are primarily KIT or PDGFRA mutations, which lead to the susceptibility of these tumors to small-molecule tyrosine kinase inhibitors such as imatinib and sunitinib. However, previous studies have shown that patients with a PDGFRA D842V mutation in GISTs have a very low rate of response to imatinib treatment. Therefore, novel tyrosine kinase inhibitors (TKIs) are currently being evaluated in clinical trials to treat GISTs harboring a PDGFRA D842V mutation. Anaplastic lymphoma kinase (ALK) overexpression was not expected to be present in the GIST, and it has been used as a biomarker to distinguish GISTs from other types of mesenchymal tumors.

Here, we report a 37-year-old male patient who presented with a large mass in the right upper abdomen and was subsequently diagnosed with a GIST harboring a PDGFRA D842V mutation. We unexpectedly found that the GIST in this patient exhibited simultaneous ALK expression.

This is the first case reported of a GIST with ALK expression. This rare phenomenon suggests that the diagnosis of a GIST cannot be excluded absolutely if a tumor exhibits ALK expression. In addition, ALK may be a potential therapeutic target for patients with imatinib-resistant stromal tumors.