Ki-1 positive large cell lymphoma of the orbit

Anaplastic large cell lymphoma (ALCL) positive for the cell marker Ki-1/CD30 is a recently recognized high grade lymphoma. The authors present a case of a three-year-old female child with a rapidly growing sino-orbital lesion with central nervous system extension, suggestive of rhabdomyosarcoma. The child presented a clinical challenge for prompt diagnosis and treatment. Histologically, the unusual tumor showed a mixture of large malignant lymphocytes and histiocytes. Immunohistochemically, the malignant lymphocytes showed positive reactivity to LCA, Ki-1, CD3, UCHL-1. The histiocytes were positive for KP-1 and lysozyme. There was complete resolution of the lymphoma. To the authors' knowledge, this is the first case of Ki-1+ ALCL lymphoma involving the orbit of a child.