Adult T‐cell leukemia/lymphoma with angioimmunoblastic T‐cell lymphoma‐like feature and molecularly confirmed RHOA Gly 17 Val (G17V) 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. <italic>Epstein‐Barr virus encoded RNA</italic>‐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 <italic>RHOA Gly 17 Val (G17V)</italic> 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. [ABSTRACT FROM AUTHOR]