Table 1 Clinical and pathological features to consider before diagnosing inflammatory myofibroblastic tumour (IMT)

Features that favour IMT		Features that argue against IMT
Child or young adult		Middle-aged or older adult
Mass in lung or soft tissue of abdomen, pelvis, or retroperitoneum		Mass in skin or subcutis, lymph node, spleen, or bladder
Diffuse inflammatory infiltrate with prominent plasma cells		Patchy, predominantly lymphocytic inflammatory infiltrate
Mild nuclear atypia including scattered ganglion-like cells		Moderate to severe nuclear atypia with hyperchromasia
Low mitotic rate without atypical forms		Atypical mitoses
ALK positivity by immunohistochemistry or ALK gene rearrangement		Necrosis