A Case of Dendritic Cell Neurofibroma With Pseudorosettes.

Dendritic cell neurofibroma with pseudorosettes (DCNP) is a rare benign peripheral nerve sheath tumor. Till date, 34 cases of DCNP arising from various sites have been reported. Histopathologically, DCNP is known to present with characteristic pseudorosettes, in which a type II cell is surrounded by type I cells. In the present report, we discuss the rare case of a 63-year-old man diagnosed with DCNP on the left flank (size: approximately 10 mm). On microscopic examination of the resected lesion, we observed the characteristic pseudorosettes with centrally placed type I cells, which exhibited small, dark, slightly irregular oval nuclei with nuclear inclusions, surrounded by type II cells, which showed a large pale nucleus with a constriction, a small nucleolus, and mildly eosinophilic cytoplasm. The type II cells were positive for S-100, CD57, LAMP2, fascin, and factor XIIIa. Although previous reports have suggested that type II cells exhibit a dendritic form, our immunohistochemical analyses revealed that these cells were dermal interstitial dendritic cells.