The final diagnosis of this patient was based on FNAC of the cervical lymph node, which revealed atypical lymphocytes with finely clumped chromatin, prominent nucleoli, and vacuolated cytoplasm, all of which are consistent with Burkitt lymphoma, and IHC, which revealed positive B cell markers and a Ki67 index of 100%. The gene discussed is MKI67; the disease is Burkitt lymphoma.