Aims: The present series describes 15 cellular neurothekeomas whose clinicopathologic features indicate a close relationship to dermatofibroma.
Methods: Retrospective clinicopathologic study.
Results: Lesions preferentially occurred in adolescents to young adults on the upper half of the body, often clinically diagnosed as some kind of fibrohistiocytic tissue response. Besides characteristic whorled nests to fascicles of palely eosinophilic epithelioid cells all lesions showed variable clues pointing to dermatofibroma: acanthosis, ill-defined storiform periphery, peripherally accentuated prominent sclerosis and lymphocytic demarcation/infiltration. All cases were positive with NK1C3 (CD 57), Ki-M1p and proliferating cell nuclear antigen, 7 for neuron specific enolase, 5 for factor XIIIa, 6 for smooth muscle actin and 3 with E9, an anti-metallothionein marker. These findings are similar to other types of dermatofibromas, the variability of the profile being best explained by time cycle and function dependent changes. Ultrastructurally, two cases showed microfilaments, attachment plaques, prominent pinocytosis and focal remnants of basal lamina. A careful study of data and microphotographs from the literature reveals that in many cases similar conclusions can be reached. Obvious discrepancies are most likely due to the confusion with myxoid neurothekeoma, a well circumscribed, more spindly and myxoid, S 100 positive lesion of Schwannian origin.
Conclusion: According to our results cellular neurothekeoma seems to be a whorled-nested to plexiform epithelioid variant of dermatofibroma.