Fine needle aspiration cytology in diagnosis and management of childhood small round cell tumours

Abstract

Fine needle aspiration (FNA) cytology is accepted for diagnosing malignant tumours in adults. However, it has been slow in gaining acceptance among paediatricians and has only been used at some centres in the routine diagnosis of childhood tumours. The aims of this thesis were to study 1: the diagnostic accuracy of FNA cytology and II: the usefulness of immunocytochemistry (IC) and molecular techniques to aid the diagnosis of cytomorphology of the small round cell tumours (SRCTs) in childhood.

This is a retrospective study and the patients were retrieved from diagnostic files from the units of Paediatric Oncology and Cytology, Karolinska Hospital, Stockholm. Patient records, cytological and histological slides were reviewed. Fresh or archival FNA material was used for IC and molecular techniques. These included image cytometry (ICM) for DNA content, interphase fluorescence in situ hybridisation (FISH) for 1p deletion and N-myc amplification in neuroblastic tumours (NT), and interphase FISH for the diagnostic EWS gene (22q12) rearrangement in Ewing's sarcoma/peripheral primitive neuroectodermal tumours (pPNET). FNA cytology correctly diagnosed and classified 85/94 patients (90.4%) with SRCTs at primary disease into lymphoma (27/27: B-cell lymphoma 9/9; lymphoblastic lymphoma 8/8; Ki-1 anaplastic large cell lymphoma 2/2; Hodgkin's disease 6/6; leukemic lymphadenopathy 2/2), rhabdomyosarcoma (16/20), NT (21/24), and Ewing's sarcoma/pPNET (21/23). Therapy was based on FNA diagnosis alone together with clinical stage in 57 of 94 patients (60.6%) after primary work-up. Surgery for diagnosis was in these cases obviated. Forty-one FNAs correctly diagnosed relapse in 29 and excluded relapse in 12 cases. There was no false positive or negative diagnosis of malignancy. The INA material was insufficient for evaluation in one case each of ganglioneuroma, rhabdomyosarcoma and necrotic neuroblastoma, respectively (2.2% of 135 aspirations). All three patients with false primary diagnoses and four with a closest diagnosis of small round cell sarcoma (including 2 relapses) were diagnosed without IC or with aid of a limited panel of immunomarkers. Vimentin and MIC2 were unexpectedly immunostained in tumour cells on INA material from NT, but not in corresponding surgical specimens. Different preparation and fixation techniques may explain the findings. Sixty-two molecular analyses in 18 NTs on fresh (n = 34) or archival (n = 28) FNA specimens were evaluated by ICM for DNA content (n = 20), interphase FISH for chromosome 1 or 2 number (n = 11), 1p status (n = 16), and N-myc status (n = 15) and resulted in informative results of prognostic importance in 60 (97%). FISH on aspirated interphase tumour cells from 20 Ewing's sarcoma/pPNETs demonstrated the diagnostic EWS rearrangement in 18 cases (90%) using fresh (6/7) or archival (12/13) specimens.

Conclusions: FNA cytology combined with a panel of immunomarkers allows a conclusive diagnosis that allows therapeutic decisions in children and adolescents with lymphoma, rhabdomyosarcoma, neuroblastic tumours and Ewing's sarcoma/pPNET. It is possible to use interphase FISH and ICM on FNA specimens for prognostic characterisation in neuroblastic tumours and diagnostic purposes in Ewing's sarcoma/pPNET. FNA is a rapid and atraumatic procedure, which can be performed without general anaesthesia and in our study without complications.