Abstract

A 64 year old male with a history of neurofibromatosis type 1 presented for new green to brown drainage from a "neurofibroma" on his scalp that had been present for 5 years. Clinical exam revealed a large tumor with discrete overlying nodules and several areas of purulent drainage protruding off of the left temporoparietal scalp. An MRI brain with and without contrast was significant for an 11x6.1x12.2cm heterogeneous lesion with remodeling of the adjacent bone due to mass effect but without clear signs of invasion. The tumor was narrowly resected and reconstructed with a split thickness skin graft. 

Histologic examination revealed a large endophytic multilobulated cystic lesion. There were several areas of trichelimmal differentiation consistent with a proliferating pilar cyst. However, these areas alternated with areas of pleomorphism, wild atypical keratinocytic cells, numerous mitoses, and necrosis. Adjacent to the lesion there were several neurofibroma-like lesions with comma-shaped bland spindle cells, thin whispy collagen, and mast cells. However, immunohistochemistry of these areas revealed negativity for S100 protein. 

This patient was presented at multi-disciplinary tumor board meeting and is currently undergoing radiation treatment. Further staging with a PET-CT was negative for metastatic disease. 

This exceedingly rare malignancy has a risk of local recurrence after resection and can metastasize. It has no known association with neurofibromatosis and no collision tumors with neurofibromas have been reported previously to our knowledge.