RESUMEN
Immunohistological expression of VLA1-5 and alpha 6 beta 4 integrins have been studied in 21 cases of primary neuroendocrine carcinomas of the skin (NECS), three xenografts on nude mice and one NECS cell culture. The phenotypic properties of NECS cells were largely maintained in NECS grafted on athymic nude-mice and in the corresponding cell line. Our results indicate that alpha 1 beta 1 and to a lesser extent alpha 3 beta 1, alpha 5 beta 1 are the main integrins expressed in NECS. In addition, VLA2, 4 and alpha 6 beta 4 are heterogeneously expressed in the same group of tumors and very sparsely present. These data suggest that like neuroblastoma and primitive peripheral neuroectodermal tumor (pPNET) the absence or the heterogeneous distribution of such integrins is correlated with the aggressive behaviour of NECS although long-term follow-up was not available for our cases. On the other hand, the alpha 1 expression could be regarded as a novel marker for differential diagnosis between NECS (alpha 1+) and pPNET (alpha 1-). The alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1 heterodimers in the 21 NECS studied showed an uniform pericellular staining of both the peripheral cells and central cells of the tumor islands. The predominant expression of alpha 1 beta 1 is consistent with the hypothesis of a primitive epithelial totipotential origin in NECS.