Indeterminate cell histiocytosiswith naïve cells

Histiocytoses are a heterogeneous group of disorders characterized by proliferation and accumulation of cells of mononuclear-macrophage system and dendritic cells. Histiocytoses are categorized according to the cell of origin into Langerhans cell histiocytosis (LCH), Non Langerhans cell histiocytoses and indeterminate cell histiocytosis (ICH). ICH is an extraordinary rare neoplastic dendritic cell disorder that has poorly understood histogene-sis and pathogenesis. It is characterized by a proliferation of dendritic cells, which mimic Langerhans cells immunophenotypically (posi-tive for CD1a and S-100 protein), but lack Birbeck granules characteristic of Langerhans cells. Twenty-four year-old Egyptian male was presented with reddish brown chest wall nodule. Clinical, histopatho-logical, immunohistochemical and ultrastruc-ture features are typical for ICH. He was in a good state without any evidence of recurrence or metastasis after 24 months follow up. Peculiar histopathological features were detected in the present case. Many unidenti-fied cells with Hematoxylin & Eosin Langerhans like features showed negative staining for S-100, CD1a, Langerin and CD68. In absence of cellular atypia and mitosis, the infiltrating cells showed epidermotropism that was reported once in ICH as well as neural and perineural invasion that were not previously reported. Therefore we prefer using a tenta-tively designated diagnosis; dendritic cell tumor, not otherwise specified or newly pro-posed diagnosis (Indeterminate cell histocyto-sis with naïve cells) for the present case