Primary cutaneous langerhans cell sarcoma: a report of four cases and review of the literature.

Langerhans cell sarcoma (LCS) is a rare but potentially life-threatening neoplastic condition. The diagnosis of LCS requires morphological and immunophenotypic characterization to distinguish it from other epithelioid-appearing malignancies. Four cases of LCS were encountered in the consultative practices of 2 of the authors. The patients ranged in age from 54 to 88 years of age. In 2 of the cases the patients had a history of acute myelogenous leukemia with eruptions occurring after initiation of decitabine. One patient died within 3 months of presenting with the skin eruption, whereas the other patient is in remission. In the other 2 patients, there was no antecedent history; the presentation was in the context of a solitary nodule. One patient declined treatment and died of disseminated metastatic disease. The other patient had complete excision with no evidence of recurrent or metastatic disease. In all cases, the biopsies showed a sheet-like growth of large atypical epithelioid cells. Phenotypic studies revealed positivity for CD4, CD1a, and S100 in all and variable staining for langerin, lysozyme, CD83, CD31, and CD14. Cutaneous LCS represents a terminally differentiated myeloid tumor with a variable but potentially aggressive clinical course. It may be related to a common stem cell defect given the association with acute leukemia. The morphology ranges from atypical appearing Langerhans cell to a high-grade large cell epithelioid malignancy mimicking amelanotic nodular melanoma.