Cow hooves and clover: Unusual morphology of peripheral T‐cell lymphoma

A 78-year-old male was referred with persistent lymphocytosis (12.4 × 109/L; reference range 1.0–4.0 × 109/L) with otherwise normal blood counts and leg ulceration. Dermatology review favoured pyoderma gangrenosum as the cause of leg ulceration. His peripheral blood showed abnormal lymphoid cells, some with cleaved or clover-leaf nuclei (top left and middle panels; May–Grünwald–Giemsa, objective ×100). Flow cytometry demonstrated an aberrant T-cell population negative for surface CD3 and TCRαβ/γδ but positive for cytoplasmic CD3, CD2, CD4 and CD5. Molecular studies demonstrated reproducible clonal T-cell receptor beta locus (TCRB)/T-cell receptor gamma locus (TCRG) rearrangements in lymph node and bone marrow samples. Computed tomography imaging revealed small bilateral inguinal nodes. Lymph node core biopsy showed effaced architecture with intermediate-sized, scattered pleomorphic atypical lymphoid cells (top right panel), expressing CD4 (bottom left panel), CD30 (bottom right panel), CD25, granzyme B and perforin. Although strong CD25 and CD30 expression prompted consideration of adult T-cell leukaemia/lymphoma (ATLL) and anaplastic lymphoma kinase-negative anaplastic large cell lymphoma (ALCL), negative Human T-cell lymphotropic virus-1/2 serology, preserved though variably downregulated pan-T-cell antigens and lack of sheets of anaplastic cells argued against these diagnoses. The mixed population of intermediate and larger atypical cytotoxic T cells, T-Cell Receptor-silent phenotype and consistent TCRB/TCRG clonality across specimens supported a diagnosis of CD30-positive peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS). He commenced treatment with Bv-CHP (brentuximab vedotin, cyclophosphamide, doxorubicin and prednisolone). He developed tumour lysis syndrome requiring dialysis but completed six cycles with resolution of the leg ulcers. Nodal disease has resolved, but after initial clearance, there is primary refractory lymphoma in the peripheral blood. PTCL-NOS is a rare lymphoma with a poor prognosis,1 diagnosed when more specific mature T-cell entities are excluded. The diagnosis of PTCL-NOS with strong CD30 expression and emerging evidence from the ECHELON-2 trial2 informed the choice of Bv-CHP chemotherapy,3 accepting that the benefit of brentuximab is less clear in PTCL (NOS) compared with ALCL. No funding was provided. Consent obtained from the patient for his case to be reported.