Lipoblast-like signet-ring cells in neurofibroma: a potential diagnostic pitfall of malignancy

Benign peripheral nerve sheath tumours, including neurofibroma, may occasionally contain a heterologous mature fatty component. Additional lipoblast-like cells can be occasionally identified among mature adipocytes. We report the first case of a plexiform neurofibroma from a NF1 patient containing exclusively lipoblast-like cells exhibiting morphological and immunohistochemical features identical to univaculoted lipoblasts typically seen in myxoid liposarcoma. Awareness of the possibility that an otherwise typical neurofibroma may contain lipoblast-like cells is crucial for the pathologist to avoid a misdiagnosis of malignancy. Differential diagnostic problems and histogenetic considerations are provided.