Pagetoid self-healing Langerhans cell histiocytosis in an infant.

We report Langerhans cell (LC) histiocytosis in a male infant who developed numerous papular lesions on the trunk and posterior scalp soon after birth and spontaneously recovered from the disease within 7 months. Histologically S-100-positive cells were detected in the epidermis and papillary dermis, in some lesions mostly in the epidermis. Tumor cells in the epidermis were either clustered, forming nests, or scattered singly in pagetoid fashion. Electron microscopy confirmed the presence of Birbeck granules in these cells. They exhibited many interesting features usually not found in normal LCs, including mitosis, frequent apoptosis, Birbeck granules invaginated in the nucleus, autophagocytosis of Birbeck granules, and active ingestion of extracellular material through Birbeck granules attached to cell membranes. It is suggested that either a strong epidermotropism of tumor cells or a proliferation of the resident LCs of the epidermis is responsible for this intraepidermal growth pattern. Cellular necrosis through very active apoptosis and the superficial nature of the growth might have contributed to the self-healing course in this patient.