SEER Inquiry System - Question 20041015 Details

For cases diagnosed prior to 1/1/2010:Code the Primary Site field to C809 [Unknown primary site]. The primary site of diffuse large B cell lymphoma can be either nodal or extranodal. The case described above is likely extranodal because there is no evidence of lymph node involvement. Because the extranodal site of origin is unknown, code the Primary Site to C809.

For cases diagnosed 2010 forward, refer to the Hematopoietic and Lymphoid Neoplasm Case Reportability and Coding Manual and the Hematopoietic Database (Hematopoietic DB) provided by SEER on its website to research your question. If those resources do not adequately address your issue, submit a new question to SINQ.