Neurofollicular hamartoma with strong diffuse S-100 positivity - A case report

Neurofollicular hamartoma is a recently described lesion with a distinct pi losebaceous and spindle cell proliferation. Neurofollicular hamartoma is co mposed of spindle cells haphazardly arranged in a fibromyxoid stroma closel y associated with an abnormal hyperplasia of folliculosebaceous units. Alth ough this histologic pattern has been classified as "neurofollicular," all cases reported thus far have had only scattered spindle cells with S-100 po sitivity. We present a case of neurofollicular hamartoma with strong and di ffusely positive staining of spindled cells for S-100 protein. This lesion also shows scattered positivity of spindle cells for monoclonal neuron spec ific enolase and synaptophysin. We interpret the results of immunostains of this lesion as evidence for neural differentiation. This case validates th e concept of "neurofollicular" hamartoma.