Adult T‐cell leukemia/lymphoma with angioimmunoblastic T‐cell lymphoma‐like feature and molecularly confirmed <i>RHOA Gly 17 Val (G17V)</i> mutation: A case report

We report a case of adult T-cell leukemia/lymphoma (ATLL) with angioimmunoblastic T-cell lymphoma (AITL/nTFHL-AI)-like feature. An 88-year-old Japanese woman with seropositive for the Human T-lymphotropic virus type 1 (HTLV-1) was incidentally diagnosed with generalized lymphadenopathy. Biopsy of the cervical lymph node demonstrated the proliferation of small- or medium-sized and large atypical lymphocytes associated with eosinophils, high endothelial venules, and clear cells. Immunohistochemical analysis revealed atypical lymphocytes were CD3- and CD4-positive. Atypical T cells bore the T-follicular helper phenotype (PD1, ICOS, and BCL6) and were positive for CD25 and chemokine receptor 4. Epstein-Barr virus encoded RNA-positive cells were scattered in the background via in situ hybridization. The histological findings were similar to those of AITL/nTFHL-AI; however, the immunohistochemical results did not exclude the possibility of ATLL. Southern blot analysis detected integration of HTLV-1 proviral DNA. The RHOA Gly 17 Val (G17V) mutation was detected by the peptide nucleic acid-locked nucleic acid clamp method. Finally, the patient was diagnosed with ATLL with AITL-like feature and exhibited a similar morphology, immunophenotype, and mutational signature to AITL/nTFHL-AI. ATLL mimics other types of T-cell lymphomas. Thus, in HTLV-1 endemic areas, routine screening for HTLV-1 serology is necessary to avoid misdiagnosis of other lymphoid malignancies.