DIAGNOSTIC-IMAGING OF PRIMITIVE NEUROECTODERMAL TUMOR OF THE CHEST-WALL (ASKIN-TUMOR)

Objectives. To describe the radiological features of primitive neuroec todermal tumour (PNET) of the chest wall (Askin tumour) at diagnosis a nd to analyse the radiological changes occurring as a consequence of t reatment and during follow-up. Materials and methods. Nine children wi th histologically proven PNET were studied. At diagnosis, all patients underwent chest X-ray (CXR), chest CT and bone scintigraphy; three pa tients also had MR and three had US. During treatment and follow-up, C T was performed in all patients. Results. CT demonstrated a solid hete rogeneous chest wall mass in all children at diagnosis and six had a r ib lesion. Small nodular densities in the extra-pleural fat were ident ified in three patients at diagnosis. US, performed in three patients, excluded tumour infiltration of the lung or diaphragm, which had been suspected on CT. On MR, the lesions showed high signal intensity in T 1-weighted/proton-density images and intermediate/high signal intensit y in T2-weighted images compared with muscle. Minimal chest wall invol vement was demonstrated in one case by MRI. Extensive necrosis of tumo ur mass with pseudo-cystic appearance was documented in the five patie nts who underwent chemotherapy Macroscopically complete resection was performed in five patients but there was early local recurrence after surgery in two, identified by CT in one and by MR in the other. Conclu sions. PNET of the chest wall should be considered in a child with a c hest wall mass. CT is valuable for evaluating tumour extension at diag nosis, the effects of chemotherapy and assessing tumour recurrence aft er surgery. However, CT can overestimate pleural, lung or diaphragmati c infiltration, which are better evaluated by US. MR was superior to C T in the evaluation of tumour extension in one of three patients and m ay be considered complementary to CT, particularly in very large chest wall tumours.