[Borderline between Hodgkin and non-Hodgkin lymphomas with unfavorable clinical course: a clinical, histological and immunohistochemical analysis of 33 cases within the German Hodgkin Lymphoma Study].

Reevaluation of diagnostic biopsies from 502 patients who entered the German Hodgkin Therapy trial was performed by a panel of four pathologists. Classification revealed 90% of unambiguous Hodgkin-lymphomas (HL), 1.6% of Non-Hodgkin-lymphomas (NHL) and 8.4% of cases difficult to evaluate, reflecting to the well-known problem of the border between these 2 groups of lymphoma. As these cases had the worst prognosis, a second attempt of reclassification, including immunohistochemical studies, was made, resulting in final classifying of 25% of these cases as NHL, 50% as HL, and 25% as further unclassifiable. The most common differential diagnostic problem was separating pleomorphic nodular sclerosing HL from large cell NHL's and HL with rather few Hodgkin- or Reed-Sternberg-cells from Lennerts lymphoma or angioimmunoblastic lymphadenopathy. Immunohistochemistry was helpful for the differential diagnostic decisions in these individual cases. A very high percentage of these problem cases had initially entered the trial as lymphocyte depleted HL, and the large majority of deaths came from the large cell NHL group.