Intradermal nevocellular nevus with adenoid features: Report of a case

Intradermal nevocelluar nevus is a very common hamartomatous neoplasm of the skin. The author herein reports two tumors of intradermal nevocelluar nevus in the neck occurring in a 55-year-old woman. The tumors were characterized histologically by typical intradermal nevocelluar nevus with significant areas of adenoid or glandular formations. In both tumors, hair follicles were seen in centers of the tumors. The cellular features of the adenoid areas were the same as those of solid areas. In solid areas, vague vacuolated and obvious vacuolated cells were recognized in some areas. In solid areas of the surface and lateral areas of the tumors also showed clear cut adenoid features without vacuolations. The adenoid features showed mild depositions of hemosiderins. There were gradual merges between solid areas and adenoid or glandular areas. Histochemically, the tumor cells including adenoid structures had glycogen, but had no mucins. Immunohistochemically, cells of both tumors were strongly positive for S100 protein, vimentin, NSE, NCAM, and bcl-2, and were weakly positive for synaptophysin and chromogranin. The tumor cells showed low cell proliferative potential; the Ki-67 labeling index was 2%. The tumor cells including adenoid structures were negative for CK AE1/3, CK CAM5.2, desmin, smooth muscle actin, HMB45, p53, p63, CD31, laminin, type 4 collagen, CEA. CD34, CA125, CA19-9, CD45, GFAP, KIT, PDGFRA, CD68, estrogen receptor, progesterone receptor, EMA, MUC1, MUC2, MUC5AC, and MUC6. These histological, histochemical, and immunohistocheimical findings strongly suggested that the present two tumors with adenoid structures belong to intradermal nevocelluar nevus. The formation of the adenoid architectures in the intradermal nevocelluar nevus was discussed. Possible mechanisms appear loss of cell adhesions molecules. The adenoid structures seem not to be degenerative ones. Pathologists should be aware that intradermal nevocelluar nevus may show adenoid structures to avoid diagnostic confusions, for example adenoma and adenocarcinoma of skin appendages. The occurrence of this hitherto undescribed condition in two intradermal nevocelluar nevus in a patient may imply genetic lineage. To elucidate the mechanisms of adenoid structures in intradermal nevocelluar nevus seems future work.