Aggressive epidermotropic cutaneous CD8(+) lymphoma is a distinct lymphoma that warrants inclusion as a distinct entity in future revisions of lymphoma classifications.

No abstract

Primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder (PCSMLPD) is a recently recognized entity in the 2017 World Health Organization (WHO) classification. It belongs to the T-follicular helper (TFH) lymphoproliferations. The clinical, pathologic, and molecular features of this localized disease are underresearched. We conducted a retrospective multicentric study of 60 patients with a PCSMLPD that presented as a single cutaneous lesion. Clinical, pathologic, and targeted molecular analyses were performed. PCSMLPD presented mostly as a nodule (45%), located on the head and neck area (50%) in adults (mean age: 59 y [43.3 to 75.2]). All patients had an indolent disease course, either at initial staging or during follow-up (mean: 16.6 mo [1.3 to 31.9]). Spontaneous regression was reported in 31.9% of cases. The infiltrates were most often nodular and/or diffuse, expanding in the whole dermis (78%, Pattern 1), rather than subepidermal band-like in the superficial dermis (22%, Pattern 2). Epidermotropism, folliculotropism, and capillary hyperplasia were common. The expression of TFH lineage markers was more extensive in lesions with Pattern 2, but a substantial B-cell infiltrate was seen in both types of lesions. A clonal rearrangement of the TCR genes was identified in 68% of cases. One sample of the 13 tested revealed a mutation in the DNMT3A gene among the 9 genes studied (TET2, DNMT3A, IDH2, RHOA, SETD2, PLCG1, STAT3, STAT5B, and CD28). PCSMLPD follows a benign clinical course and can spontaneously regress after biopsy. Although PCSMLPD expresses TFH lineage markers, mutations usually found in angioimmunoblastic T-cell lymphomas are uncommon.

Summary Background Primary cutaneous lymphomas (PCLs) are a heterogeneous group of T‐cell (CTCL) and B‐cell (CBCL) malignancies. Little is known about their epidemiology at initial presentation in Europe and about potential changes over time. Objectives The aim of this retrospective study was to analyse the frequency of PCLs in the French Cutaneous Lymphoma Registry (GFELC) and to describe the demography of patients. Methods Patients with a centrally validated diagnosis of primary PCL, diagnosed between 2005 and 2019, were included. Results The calculated incidence was unprecedently high at 1·06 per 100 000 person‐years. The number of included patients increased yearly. Most PCL subtypes were more frequent in male patients, diagnosed at a median age of 60 years. The relative frequency of rare CTCL remained stable, the proportion of classical mycosis fungoides (MF) decreased, and the frequency of its variants (e.g. folliculotropic MF) increased. Similar patterns were observed for CBCL; for example, the proportion of marginal‐zone CBCL increased over time. Conclusions Changes in PCL frequencies may be explained by the emergence of new diagnostic criteria and better description of the entities in the most recent PCL classification. Moreover, we propose that an algorithm should be developed to confirm the diagnosis of PCL by central validation of the cases.

Clinical features and outcome are the most discriminative to differentiate the two entities. Even histological and molecular markers were not fully specific; abnormal vs. normal T-cell phenotype and perforin expression may constitute helpful tools.