NCIt definition : Unresectable unilateral tumor infiltrating across the midline, with or without regional
lymph node involvement; or localized unilateral tumor with contralateral regional
lymph node involvement; or midline tumor with bilateral extension by infiltration
(unresectable) or by lymph node involvement. The midline is defined as the vertebral
column. Tumors originating on one side and crossing the midline must infiltrate to
or beyond the opposite side of the vertebral column. (cancer.gov);
Alternative definition : NCI-GLOSS: In stage 3 neuroblastoma, the tumor (1) cannot be completely removed during
surgery and has spread from one side of the body to the other side and may also have
spread to nearby lymph nodes; or (2) is in one area of one side of the body only,
but has spread to lymph nodes on the other side of the body; or (3) is in the middle
of the body and has spread to tissues or lymph nodes on both sides of the body, and
the tumor cannot be removed by surgery.;