<prompt> Which is the most common subtype of classical Hodgkin lymphoma?Mixed-cellularity typeLymphocyte-depleted typeNodular sclerosis typeLymphocyte-rich type  <response>: The WHO classification recognizes two major types of Hodgkin lymphoma: Classical Hodgkin lymphoma CHL Nodular lymphocyte predominant Hodgkin lymphoma NLPHL Classical Hodgkin lymphoma is fuher classified into four subtypes: Nodular sclerosis - most common form of Hodgkin lymphoma, constituting 65 to 70 of cases. Mixed-cellularity - constitutes about 20 to 25 of cases. Lymphocyte-rich - uncommon Lymphocyte-depleted - least common, 5 cases, predominantly seen in HIV-positive patients. The Reed-Sternberg cells in Classical HL have a similar distinctive immunophenotype: Positive for CD15, CD30 and weakly positive for PAX5 a B-cell transcription factor Negative for other B-cell markers CD20, CD45 leukocyte common antigen and T-cell markers In case of Nodular Lympocyte predominant Hodgkin lymphoma NLPHL: RS cell variant Popcorn cells are present, which are CD15 and CD30 negative and positive for CD20. 