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

Abstract

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.

Cutaneous reactive B‐cell lymphoid proliferations

“…However, as previously mentioned, a debate exists whether reactive CLH can show clonal B‐cells by molecular methods. SM‐TLPD can show both clonal T‐cell and B‐cells 167 …”

Clonal B‐cell proliferations developing in the background of primary cutaneous CD4+ small/medium T‐cell lymphoproliferative disorder: A case series

“…They are responsible for B‐cell differentiation and germinal center reaction; germinal center B‐cells are dependent on TFHs for survival and proliferation. It is because of this that clonal B‐cell proliferations and B‐cell lymphomas may co‐occur in the background of TFH‐derived lymphomas, most with EBV positivity, and this has been well characterized for TFH lymphoma, especially “TFH lymphoma, angioimmunoblastic‐type.” 1–4 The presence of B‐cell proliferations has also recently been described in CD4 + PCSM‐LPD in two cases, one with accompanying B‐cell clonality 5 . We expand on this and report four cases of CD4 + PCSM‐LPD with accompanying clonal B‐cell proliferation, and one longstanding case of CD4 + PCSM‐LPD, in the background of which a B‐cell lymphoma developed.…”

“…This case may be representative of the advanced stage of the spectrum of B‐cell proliferations that may be encountered in primary cutaneous CD4 + PCSM‐LPDs. Hence, as with the nodal counterpart of TFH lymphoproliferations, and as Bakr et al 5 have also commented, primary cutaneous CD4 + PCSM‐LPD cases too may harbor accompanying clonal B‐cell proliferations and if left untreated, have the potential to evolve into B‐cell lymphomas. Based on our experience, the association of the accompanying clonal B‐cell proliferations with EBV seems to be less prominent, in comparison to TFH lymphoma, having only been seen in one of our five cases and to the best of our knowledge, not previously been reported in the literature.…”

“…[1][2][3][4] The presence of B-cell proliferations has also recently been described in CD4 + PCSM-LPD in two cases, one with accompanying B-cell clonality. 5 We expand on this and report four cases of CD4 + PCSM-LPD with accompanying clonal B-cell proliferation, and one longstanding case of CD4 + PCSM-LPD, in the background of which a B-cell lymphoma developed.…”

Follicular T-Helper Cells in Marginal Zone Lymphoma: Evidence of an Organoid Immune Response

“…Moreover, 2 of the MZL cases included had been the source of previous diagnostic confusion with PCSM-LPD in routine practice and are the source of a separate submission. 44 In many other cases, there were occasional interfollicular rosettes of PD-1(+) cells. The effector mechanisms of TFH requires cell-cell contact, mediated as they are through synaptic delivery of membrane-bound factors 35 ; therefore, stable colocalization of T cells and target B cells is required for this function, and it is not surprising that rosettes of TFH cells around B cells may be observed in situations of TFH accumulation.…”