Clinical and pathological observations that support or controvert the malignant origin of pulmonary Langerhans' cell histiocytosis (LCH)
| Observations against a malignant origin | Observations compatible with a malignant origin |
| Clinical | |
| Occurs almost only in heavy cigarette smokers | Existence of diffuse (aggressive) forms of |
| Isolated pulmonary involvement in most cases | LCH |
| Spontaneous remission frequent | Recurrence after transplantation |
| Pathological findings | |
| Bronchocentric distribution of lesions | LC in pulmonary LCH are clonal |
| Virtual absence of LC in end stage lesions | |
| Cellular atypia rare | |
| Low rate of LC proliferation | |
LC = Langerhans' cells.