Neurothekeoma: report of a case in an infant and review of the literature

Neurothekeomas (nerve sheath myxomas) are uncommon benign tumors of nerve sheath origin. We describe an infant with a neurothekeoma and review the literature of neurothekeomas in children and adults. Neurothekeomas have been reported in 292 patients whose ages have ranged from 15 months to 84 years. They occur twice as often in women as in men. Neurothekeomas were most commonly located on the upper extremities and the head and neck. They also occurred on the trunk, the lower extremities, and mucosa. Histologic variants of neurothekeomas include classical, cellular, and mixed tumors. Surgical excision was the most common treatment. Recurrences were attributed to an incomplete excision; treatment of these tumors is by complete excision. Neurothekeomas should be included in the differential diagnosis of dermal nodules in infants and children.

Cellular 'neurothekeoma': an epithelioid variant of dermatofibroma?

AIMS

Cellular neurothekeoma is a rare benign cutaneous neoplasm with conflicting opinions regarding its histogenetic origin (nerve sheath, smooth muscle, myofibroblasts) as well as its relation to myxoid neurothekeoma (nerve sheath myxoma). The present series describes 15 cases whose clinicopathological features indicate a relationship to dermatofibroma.

METHODS AND RESULTS

In this retrospective clinicopathological study, the 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. Immunohistochemically, all cases were positive with NK1C3 (CD57), KiM1p and proliferating cell nuclear antigen, seven were positive for neurone specific enolase, five for factor XIIIa, six for smooth muscle specific actin and three for E9, an antimetallothionein marker. These findings are similar to those of conventional 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 the data and photomicrographs from the literature reveals that in many cases similar conclusions could be reached. Obvious discrepancies are most likely due to the confusion with myxoid neurothekeoma, a well circumscribed, more spindly and myxoid, S100 positive lesion of Schwannian origin.

CONCLUSION

The appearance of dermatofibromas is markedly influenced by architectural, e.g. in deep penetrating dermatofibroma, and/or cellular/stromal criteria, e.g. in epithelioid cell histiocytoma or sclerosing dermatofibroma. Cellular neurothekeoma seems to be a variant of dermatofibromas with both architectural and cellular/stromal peculiarities, i.e. plexiform pattern, epithelioid cytology and stromal sclerosis.