Prominent Blasts in Primary Cutaneous CD4+ Small/Medium T-Cell Lymphoproliferative Disorder. A Reconsideration of Diagnostic Criteria

Primary cutaneous CD4(+) small/medium T-cell lymphoproliferative disorder (PCSM-LPD), recently downgraded from a T-cell lymphoma, is a poorly characterized histopathological entity. Presenting as a solitary lesion that often grows rapidly, it may raise suspicion for a cutaneous B-cell lymphoma. However, classically, the dermal lymphoid proliferation is predominantly CD4(+) with a follicular T-helper profile and a smaller B-cell fraction. Diagnostic uncertainty may arise when B cells are present in large numbers, a B-cell clone is present, or large cell populations are seen. To meet the diagnostic criterion of PCSM-LPD, large cells should not constitute more than 30% of the infiltrate. The 2 cases presented in this article caused diagnostic uncertainty owing to the observation of high numbers of large cells and in one case the presence of a B-cell clone, on the background of otherwise typical clinicopathological features of PCSM-LPD. We review the literature specifically regarding the prevalence of large cell populations and their immunophenotypic characteristics and in light of this discuss whether a current diagnostic criterion should be reconsidered.

Automated summary

PCSM-LPD, previously classified as a T-cell lymphoma, is a poorly understood histopathological entity characterized by rapidly growing solitary lesions predominantly composed of CD4(+) lymphoid proliferation with a follicular T-helper profile and a smaller B-cell fraction. Diagnostic uncertainty may arise in cases with large numbers of B cells, B-cell clones, or large cell populations, where large cells should not exceed 30% of the infiltrate to meet diagnostic criteria.