Cutaneous plasmablastic lymphoma: retrospective comparative study of primary and secondary skin involvement

Cutaneous plasmablastic lymphoma (cPBL) is a rare and aggressive neoplasm that presents as skin nodules. Despite occurring in ~5% of PBL cases, the World Health Organization (WHO) does not distinguish primary cutaneous PBL (pcPBL) from secondary cutaneous PBL (scPBL), and their clinical differences remain poorly defined. To determine whether pcPBL represents a distinct clinical entity, we compare the clinicopathologic features, immunohistochemical profiles, and survival outcomes of pcPBL and scPBL.

Retrospective comparative study analysing 40 cases of cPBL (6 newly identified institutional cases and 34 cases from the literature), categorized as pcPBL (n = 25; no extracutaneous disease at diagnosis) or scPBL (n = 15; concurrent extracutaneous disease). Patients with pcPBL were older than those with scPBL (median 62 vs. 43 years; Mann-Whitney P = 0.018). Leg involvement was significantly associated with pcPBL (OR = 6.22; 95% CI: 1.21-31.9; P = 0.031). Disease-specific survival (DSS) analysis included 17 evaluable cases (pcPBL n = 11; scPBL n = 6). Median DSS was 42.0 months in pcPBL and 8.0 months in scPBL (log-rank χ² = 3.98; p = 0.046). Median follow-up (reverse Kaplan-Meier) was 20.0 months in pcPBL and not reached in scPBL. Cox models were directionally consistent but underpowered.

In this pooled analysis, cases presenting with primary cutaneous involvement tended to occur in older patients and more often involved the legs. However, these observations should be interpreted cautiously given small numbers and heterogeneity of the available data. Within pcPBL, EBV positivity correlated with better survival. These hypothesis-generating findings provide a basis for prospective, multi-centre studies to clarify classification, staging implications, and management of this rare lymphoma.