Pathological characteristics of gastrointestinal stromal tumours with PDGFRA mutations

AIMS: The aim of this study was to identify the characteristics of PDGFRA-mutated gastrointestinal stromal tumours (GISTs) in comparison with KIT-mutated GISTs. METHODS: A total of 151 GISTs were examined for KIT and PDGFRA mutations, and clinical and histopathological parameters were evaluated and analysed statistically according to mutation status. RESULTS: KIT and PDGFRA mutations were detected in 123 (81.5%) and 15 cases (9.9%), respectively. Clinically, all PDGFRA-mutated GISTs were located in the stomach with no recurrences and tumour-related deaths were noted. Pathological parameters associated with PDGFRA mutations were epithelioid and mixed type, low to moderate cellularity, moderate to severe intratumoural lymphocytic infiltration, prominent myxoid change, frequent rhabdoid cells and multinucleated giant cells, increased cellular pleomorphism, low mitotic count, and lower risk assessment (p < 0.05). Compared with KIT-mutated GISTs, PDGFRA-mutated GISTs had unique histopathological patterns, intermingling of spindle and epithelioid cells, and/or a jigsaw puzzle-like arrangement of epithelioid cells. CONCLUSIONS: PDGFRA-mutated GISTs have distinctive histological patterns that are differentiated from KIT-mutated GISTs. The algorithmic approach by a combination of several distinguishing histological and immunohistochemical features between KIT- and PDGFRA-mutated GISTs might be helpful in predicting the mutated gene of each GIST on pathological examination.ope