Cutaneous neuroblastoma (CN) is a rare tumor in adults. Histologically CN can be confused with other small, round cell tumors, especially with Merkel cell tumor. This is the second case that we have encountered in a 6-year period. A 46-year-old man with severe adult respiratory distress syndrome had a 2.5 x 2.0 x 2.0-cm, rapidly growing, fleshy nodule over his nose. The clinical impression was pyogenic granuloma (PG) or keratoacanthoma (KA). Histologically, the tumor showed undifferentiated cells with frequent Homer Wright rosettes and mitoses. Conventional special stains and a broad panel of immunohistochemical markers were applied that were positive only for neuron-specific enolase. Ultrastructurally the cells contained dense-core granules and immature desmosomes. The diagnosis of CN was made and an extensive radiologic and laboratory workup was initiated, but the results were negative for another primary tumor. The patient subsequently died and a thorough postmortem examination revealed multiple visceral metastatic lesions but no primary tumors in the adrenal glands, the sympathetic chain, or the central nervous system.
Conclusions: (a) CN does occur in adults and can mimic other fast-growing tumors of the skin, for example, PG or KA; (b) the diagnosis of CN requires the combined use of immunohistochemistry and electron microscopy; and (c) the dermatologist should be aware of this rare, but important, tumor because its primary cutaneous manifestation may enable early recognition.