Solitary congenital histiocytoma: two cases.

Background. Solitary histiocytoma is an uncommon form of Hashimoto-Pritzker syndrome and an exceptional type of histiocytosis with cells of undetermin ed origin. A solitary often ulcerated congenital nodule is generally observ ed. We report two cases, one of each form. Case reports. Both cases presented an ulcerative budding congenital tumefac tion of the plantar aspect of the right foot for the first child and the pa rieto-axillary region in the second. Histology disclosed a granulomatous in filtrate of histiocytes positive for specific immunolabels (protein S100 an d CD1a). In the first case, electron microscopy revealed histiocytes devoid of Birbeck granules and myelinoid bodies leading to the diagnosis of Lange rhans histiocytosis with cells of unknown origin. In the second case, 18 p. 100 of the cells contained Birbeck granules. There has been no recurrence after a 5-year follow-up in a case. Discussion. These cases recall the congenital nature of some types of solit ary histiocytomas. Indeed, congenital Langerhans histiocytoma can occur as a unique nodule. The tumefaction may lie in any localization. Histological diagnosis is required. The benign nature of these lesions is confirmed by t he absence of distant lesions and the lack of recurrence after complete exc ision. About a dozen cases have been reported. Most have been Hashimoto-Pri tzker syndromes. Only one case has been reported with cells of undetermined origin. The diagnosis of histiocytosis with cells of undetermined undeterm ined origin is made when the ultrastructure study demonstrates the vacuity of the histiocyte cytoplasm. This condition is similar to Hashimoto-Pritzke r syndrome by the absence of recurrence and systemic diffusion. It can howe ver be observed in adults. The undetermined cell types would correspond dif ferent phases of Langerhans cell maturation or involution.