Primary Cutaneous Sarcomatoid Anaplastic Lymphoma Kinase-Positive Anaplastic Large-Cell Lymphoma With Linear Distributional Lesions.

We report a case of cutaneous anaplastic lymphoma kinase-positive anaplastic large-cell lymphoma (ALCL) with linear distributional lesions and sarcomatoid histologic features. A sarcomatoid variant is the rarest morphological pattern of ALCL. Interestingly, the morphology of tumor cells in the present case transitioned from a sarcomatoid variant of ALCL at first diagnosis to a classic variant at relapse. The case is a diagnostic challenge considering both the clinical and histologic aspects. Awareness of the sarcomatoid variant of ALCL and its morphological changes can lead to a correct diagnosis.