Recurrent inflammatory myofibroblastic tumors harboring PIK3CA and KIT mutations.

Inflammatory myofibroblastic tumour (IMT) is a relatively rare soft tissue malignancy. It exhibits locally aggressive behavior with a tendency for local recurrence and rare metastasis, and rare recurrent IMTs may show histological progression. The genetic hallmark of IMT is ALK rearrangement from chromosome arm 2p, but gene mutations involved in IMT remain poorly understood. The aim of the present study was to perform a pairwise comparison of the gene mutations occurring in primary and recurrent IMT from the same patient. We conducted a high-throughput analysis of 238 known mutations of 19 oncogenes in pairwise comparison primary and recurrent samples from 2 patients of IMT using Sequenom MassARRAY technology. Our results revealed 2 mutations in 2 recurrent lesion samples, including one in exon 11 of the KIT gene, resulting in a T-C substitution at position 1727 (L576P), the recurrent sample underwent histologic progression with "pleomorphic undifferentiated sarcoma-like" transformation; the other mutation was in exon 19 of the phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) gene, resulting in a G-A substitution at position 1624 (E542K). Moreover, no any mutation was found in the primary lesion samples from 2 patients. Our findings suggest that variable genome changes might be present in IMT, especially during the progression from a primary tumour to recurrence. To the best of our knowledge, no such longitudinal study of IMT has been undertaken previously.