Staging of NHL according to international paediatric NHL staging system ⁽²²⁾

Stage I:

·  A single tumour not in the mediastinum and abdomen.

Stage II:

·  A single extra nodal tumour with regional LN involvement

·  Two or more nodal areas on the same side of the diaphragm

·  A primary gastrointestinal tract tumour (usually in the ileocecal area, with or without involvement of associated mesenteric nodes, that is completely resectable (if ascites or extension of the tumour to adjacent organs, it should be regarded as stage III)

Stage III:

· Two or more extra nodal tumours (including bone or skin)

·  Two or more nodal areas above and below the diaphragm

·  Any intrathoracic tumour (mediastinal, hilar, pulmonary, pleural, or thymic)

· Intra-abdominal and retroperitoneal disease, including liver, spleen, ovary, and/or kidney localizations, regardless of degree of resection.

· Any paraspinal or epidural tumour, whether or not other sites are involved.

· Single bone lesion with concomitant involvement of extra-nodal and/or non-regional nodal sites.

Stage IV:

· Any of the above findings with initial involvement of the CNS, bone marrow, or both.

Stage IV, due to CNS disease is considered if one or more of the following applies

· Any lymphoma cells by cytology in CSF.

· Any CNS tumour mass by imaging.

· Cranial nerve palsy (if not explained by extracranial tumour).

· Clinical spinal cord compression.

· Parameningeal extension: cranial and/or spinal

Stage IV disease, due to bone marrow involvement

 Defined by morphologic evidence of any lymphoma cells in a bone marrow aspirate.