# Primary Cutaneous CD4+ Small/Medium T-cell Lymphoproliferative Disorder in a Young Japanese Male Patient

## TL;DR

A young Japanese man was diagnosed with a rare skin lymphoproliferative disorder after initial misdiagnosis and treatment failure.

## Contribution

This case report highlights the possibility of misdiagnosing young patients with PCSM-LPD as pseudolymphoma.

## Key findings

- The patient's skin biopsy showed CD4+ T-cell dominance and clonal T-cell expansion.
- The lesion resolved after treatment with fludroxycortide tape.
- NFATc1 staining was negative, supporting the diagnosis of PCSM-LPD over pseudolymphoma.

## Abstract

A 34-year-old man became aware of an erythematous nodule on the left nasal wing. He was treated with topical steroids and oral antibacterial agents at his local doctor, but his condition did not improve, and he was referred to our hospital. A skin biopsy revealed diffuse cellular infiltration through the dermis. No epidermotropism was seen. The major infiltrate was small to medium-sized lymphoid cells. The number of CD3+ cells was almost the same as that of CD20+ cells, while CD4+ cells were dominant over CD8+ cells. Atypical lymphocytes were positive for BCL6 and PD-1. Polymerase chain reaction (PCR) analysis of immunoglobulin heavy chain and T-cell receptor gene rearrangements on paraffin-embedded tissue sections revealed a clonal expansion of T-cells. The patient was diagnosed as having primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder (PCSM-LPD) and treated with fludroxycortide tape. The red nodule completely disappeared after three months. Nuclear staining for nuclear factor of activated T-cells c1 (NFATc1), which had been suggested to be useful in distinguishing PCSM-LPD from pseudolymphoma, was negative in our case.

Our case was considered to be typical of PCSM-LPD among existing reports of PCSM-LPD from Japan, except for the young age of the patient. Our case suggested that young cases with PCSM-LPD may have been misdiagnosed with cutaneous pseudolymphoma (CPL), which may be one of the reasons why this type of lymphoproliferative disorder has been reported to occur in elderly people.