Keloids and hypertrophic soars of Caucasians show distinctive morphologic and immunophenotypic profiles

The aim of this study was to identify possible morpho-phenotypic difference s between keloids (K) and hypertrophic scars (HS) in a Caucasian population . Young HS (less than or equal to 1year of age) presented a high number of diffusely distributed spindle-shaped cells (alpha -smooth-muscle actin(+) a nd fibronectin(+)). Fully developed HS (>1 year of age and <3 years of age) were characterized by the frequent presence of distinct collagenous cellul ar nodules (cells: <alpha>-smooth-muscle actin(+) and fibronectin(+)). Old HS (greater than or equal to3 years of age) showed widespread collagenizati on phenomena. The histological profile of K was not related to the age of t he lesion and was characterized by the almost constant presence of abnormal ly thick, hyalinized collagen fibers, the presence of collagenous cellular nodules, and variable-albeit lower than in HS-expression of alpha -smooth-m uscle actin and fibronectin. Ultrastructurally, myofibroblasts were the pre dominant cell type in young and fully developed HS and in K. The immune-cel l infiltrate was composed of CD3(+), CD45RO(+), CD4(+), human lymphocyte an tigen (HLA)-DR+, and lymphocyte function associated antigen (LFA)-1(+) T ly mphocytes, strictly associated with CD1a(+)/CD36(+), HLA-DR+, and intercell ular adhesion molecule (ICAM)-1(+) dendritic cells, both in HS and K. Howev er, different amounts of immune cells were observed in relation to the type and age of the lesion, and these findings support the hypothesis that cell -mediated, major histocompatibility complex (MHC)-class II-restricted immun e responses play an important role in the development of HS and K.