Neuroblastoma-like neurilemoma

We report three cases of neurilemoma occurring in the superficial soft tissue of the palm, posterior neck, and flank that closely resembled neuroblastoma by virtue of a predominance of small, round hyperchromatic schwann cells with scant cytoplasm which, in one case formed perivascular rosettes and, in the others, giant rosettes with central collagen cores. Although the diagnosis of neuroblastic tumor was seriously entertained in all cases, the diagnosis of a schwannoma was substantiated by the finding of focal areas of conventional schwannoma and by the typical immunophenotypic profile. All tumors strongly and diffusely expressed S-100 protein but lacked neurofilament protein, protein gene product (PGP), and synaptophysin. Ultrastructurally the cells contained slender cytoplasmic processes invested with basal lamina, but no dense core granules. All were excised conservatively, and none has recurred during the 2, 12, and 27 month follow-up periods.