Primary Cutaneous Anaplastic Large Cell Lymphoma With Positive ALK Expression and a Rapidly Progressive Cutaneous Nodule

Primary cutaneous anaplastic large cell lymphoma (pcALCL) is a distinct entity from systemic ALCL (sALCL). sALCL usually shows immunohistochemical positivity for anaplastic lymphoma kinase (ALK) and epithelial membrane antigen (EMA), whereas these tests are negative in pcALCL. In contrast to sALCL, pcALCL is rarely found in children and young adults. We present here a case of a rare clinical condition in a 21-year-old woman, who has pcALCL with positive ALK and patchy EMA expression. She experiences a large, rapidly growing nodule without any outside-nodule manifestation. In conclusion, both ALK and EMA expression alone cannot distinguish pcALCL from secondary skin involvement by a sALCL.