Constant small‐cell changes and variable LEF1 expression in DUSP22‐rearranged primary cutaneous anaplastic large‐cell lymphoma: Analysis of the repeated biopsies of three patients

Abstract

AbstractDUSP22‐rearranged primary cutaneous anaplastic large‐cell lymphoma (pcALCL) has a biphasic histological pattern defined by large dermal atypical lymphocytes and epidermotropic small lymphocytes resembling pagetoid reticulosis, but the positivity rate of the biphasic pattern in DUSP22‐rearranged pcALCL is unknown. Immunohistochemically, LEF1 expression in >75% of tumor cells is associated with DUSP22‐rearrangement (DUSP22‐R) in systemic ALCL. However, whether this association applies to pcALCL remains unclear. To analyze these pathological clues for screening DUSP22‐R, we reviewed 11 skin biopsies from three patients with DUSP22‐rearranged pcALCL. All specimens showed a biphasic pattern, of which three showed nonpagetoid infiltration of the epidermis. In all lesions, small‐cell changes of tumor cells were observed not only within the epidermis but also under the epidermis. LEF1 positivity rates varied by lesion (range: 30%–90%, mean: 59.6%) with only three patients expressing LEF1 in more than 75% of tumor cells. In conclusion, the biphasic pattern was a constant finding in DUSP22‐rearranged pcALCL, but it was not always pagetoid reticulosis‐like. The recognition of small‐cell change outside the epidermis may be helpful in diagnosing DUSP22‐rearranged pcALCL. However, LEF1 expression was variable and its diagnostic usefulness may be limited.