Indeterminate cell tumor [histiocytosis]

Indeterminate cell tumor [ICT; histiocytosis] is a rare disorder characterized by accumulation of histiocytes that do not fulfill the phenotypic criteria designated for Langerhans cells [LC]. The cells classified as "indeterminate" exhibit overlapping features between dendritic cells and histiocytic cells by showing variable reactivity for CD1a and positivity for S-100 protein and CD68. Ultrastructurally, absence of Birbeck granules, a feature consistent with LC, epitomizes the lesional cells. Herein, we report a case of ICT in a new born emphasizing its histogenesis and clinical, morphologic, immunohistochemical, and ultrastructural features