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Next-generation sequencing performed on peripheral blood was negative for pertinent gene alterations. In the recent fifth edition of the WHO, these subtypes are listed separately within the hierarchical structure of PCTCLs, with the term ‘pcPTCL NOS’ being reserved for rare cases that do not fit under any other described entity.1 In contrast, the 2022 International Consensus Conference (ICC) classification system does not include pcPTCL-NOS in its diagnostic framework.3 At the outset of the patient’s clinical course, MF was considered in the differential diagnosis; however, this case lacks several defining features seen in MF. According to the WHO classification, a diffuse or nodular dermal infiltrate, sometimes extending to the subcutis, is the defining histological finding in pcPTCL-NOS.1 In contrast, classic MF is characterised by epidermotrophism of small to medium-sized cells with cerebriform nuclei, sometimes forming Pautrier microabscesses.2 While some cases of transformed MF have been associated with the appearance of a CD20 component, recent studies suggest that dense CD20 component is more commonly attributable to a reactive B-cell population instead of true aberrant CD20 expression by T-lymphomatous cells.2 In contrast, aberrant CD20 expression has been documented in about a fifth of cases of pcPTCL-NOS.1 4 In our case, the neoplastic population showed true coexpression of CD3 and CD20 as well as T-cell receptor clonality, supporting the diagnosis of pcPTCL-NOS. [...]our case showed loss of pan T-cell markers CD2 and CD7 and a high Ki-67 proliferation rate, a pattern more consistent with pcPTCL-NOS. Peripheral T-cell lymphomas unspecified presenting in the skin: analysis of prognostic factors in a group of 82 patients.
