A Case of ALK-Negative Anaplastic Large Cell Lymphoma Presenting as a Solitary Cutaneous Nodule

Anaplastic large cell lymphomas (ALCLs) are a group of CD30 positive T-cell non-Hodgkin lymphomas, accounting for only 3% all lymphomas. As per the 2017 World Health Organization updated classification, there four variants ALCL: anaplastic lymphoma kinase (ALK) positive, ALK negative, primary cutaneous, and breast-implant associated. The different ALCL share overlapping clinical presentations pathologic features, creating diagnostic challenge. A 71-year-old woman with past history presented progressively growing nodule on her back approximately 3 months. Physical exam demonstrated 8.0 x cm pink nodular indurated plaque located left upper back. punch biopsy lesion revealed medium to mononuclear cells nuclear pleomorphism, hyperchromasia, scattered mitotic figures. Immunohistochemistry that were negative ALK. Based histopathologic findings, diagnosis was rendered. Differential included cutaneous involvement by systemic ALK(-) ALCL. This case demonstrates importance clinicopathologic correlation in diagnosing guiding therapy.