Diagnostic challenges and considerations in CD30-negative classical Hodgkin lymphoma from biopsy specimens.

This study aimed to investigate the clinicopathological features and diagnostic strategies of CD30-negative classic Hodgkin lymphoma (cHL) based on core needle biopsy specimens. Six cases diagnosed at Yantai Yuhuangding Hospital and Beijing Gaobo Boren Hospital were retrospectively analyzed. The diagnosis was established through integrated evaluation of histomorphology and immunohistochemical (IHC) profiling. All cases underwent repeated CD30 immunostaining using multiple antibody clones and platforms to confirm true CD30 negativity. The cohort comprised five males and one female (male-to-female ratio 5:1), with a median age of 17.5 years (range: 6-86 years). Histological subtypes included four cases of mixed cellularity and two of nodular sclerosis, all demonstrating characteristic morphological features of cHL. CD30 expression was entirely absent in five cases and weakly positive in scattered tumor cells in one case. To ensure diagnostic accuracy, repeat biopsies were performed in four patients. IHC analysis revealed consistent expression of PAX5, C-MYC, ATF3, and p53 in all six cases, with variable positivity for CD20 (3/6), LCA (1/6), MUM1 (4/6), OCT2 (4/6), and BOB.1 (1/6). Epstein-Barr virus-encoded RNA (EBER) was positive in five cases (83.3 %), with none of the cases undergoing flow cytometry (FCM). Five patients received ABVD chemotherapy; four achieved complete remission, one died, and one was lost to follow-up. IDiagnosis was established based on histomorphological identification of Reed-Sternberg-like cells within a characteristic inflammatory background, in conjunction with an extended immunophenotypic panel. CD30 immunostaining was repeated using different clones and platforms to exclude technical artifacts. In cases with persistent CD30 negativity, complete excision was performed when feasible, and diagnosis was confirmed only if R-S-like cells concurrently exhibited: (1) variable or weak CD20 and LCA expression, never both strongly positive; (2) weak or absent PAX5 and MUM1; (3) discordant BOB.1 and OCT2 expression; and (4) positive c-MYC, p53, and ATF3 nuclear staining. Cases failing to meet all criteria were excluded. In conclusion, CD30-negative cHL diagnosed on limited biopsy material tends to affect younger male patients and retains typical morphological and immunophenotypic hallmarks of cHL. A thorough diagnostic approach incorporating multi-clone CD30 IHC and repeat sampling when necessary is crucial to avoid misdiagnosis in these diagnostically ambiguous cases.