Clinical, Pathologic, and Molecular spectrum of Angioinmmunoblastic T-cell Lymphoma Cutaneous Lesions

Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive malignancy that frequently presents with extranodal involvement. Cutaneous tropism is clinically and histopathologically variable, which may pose a diagnostic challenge. We conducted a retrospective analysis of 40 samples of 20 cases of cutaneous AITL, focusing on the clinicopathologic and molecular correlations between skin and lymph node (LN) samples. In all cases, cutaneous involvement was concurrent with or followed the diagnosis of nodal AITL, with no cases preceding systemic involvement. Clinically, cutaneous AITL presented in 2 main forms: an evanescent rash and persistent lesions, with histopathology revealing diverse infiltration patterns, including perivascular, nodular, granulomatous, panniculitic, vasculitis, and epidermotropic. Clinical presentation and histologic patterns tend to correlate. Histopathologically, plasma cells were present in 15/22 skin samples, 5 of them being kappa-light restricted but polytypic in corresponding LNs. Epstein-Barr virus+ B cells were present in 10 cutaneous lesions and were already present in corresponding LNs. Molecular studies found correlations in all but one case between LN and skin, particularly in the presence of RHOA and TET2 mutations, which were identified in 8 of 12 cases. Molecular analysis was also informative in 4 cases with low levels of infiltration. The study also highlighted unique cases with distinct clinical and histopathologic patterns coexisting in the same patient over time. One case exhibited simultaneous granulomatous and epidermotropic patterns in different skin lesions. Four cases of cutaneous B-cell lymphomas associated with AITL were identified. Our study underscores the importance of integrating clinical, histopathologic, and molecular data to accurately diagnose cutaneous AITL.