Abundant eosinophil infiltration in a neurofibroma

We report a case of sporadic cutaneous neurofibroma showing diffuse eosinophil infiltration in a 72-year-old woman. The neurofibroma had been on the skin of the left anterior shoulder for approximately 10 years. The presence of mast cells is well known in neurofibroma. However, infiltration of neurofibromas by eosinophils has not yet been documented. We propose that eosinophil infiltration is mediated by the effects of mast cells. We suggest that this is indirect evidence that mast cells in some neurofibromas are not quiescent but active. We also reintroduce the notion that acid-fast stains are a useful method to discriminate between mast cell granules and eosinophil granules.