SOLITARY CONGENITAL INDETERMINATE CELL HISTIOCYTOMA

Background.-Indeterminate cell proliferations are rarely described in the literature. We present a case of a patient who presented at birth with a solitary lesion that spontaneously regressed. Observations.-Five cases of indeterminate cell proliferations have been described in the literature. Their clinical patterns display some common features including adult onset, usually with multiple lesions and a relatively benign clinical course. This patient presented at birth with a single lesion and spontaneous regression, as one would expect with congenital self-healing reticulohistiocytosis. Biopsy confirmed a dermal histiocytic nodule that was predominantly CD1 and S100 positive. Unlike patients with congenital self-healing reticulohistiocytosis, however, electron microscopy failed to demonstrate Birbeck granules. Conclusion.-Indeterminate cell proliferations are a distinct entity. This presentation expands the range of clinical manifestations reported. It also suggests a close relationship between indeterminate cells and Langerhans cells.