%0 Journal Article
%T p16 Expression Is Lost in Severely Atypical Cellular Blue Nevi and Melanoma Compared to Conventional, Mildly, and Moderately Atypical Cellular Blue Nevi
%A Laura M. Chang
%A David S. Cassarino
%J ISRN Dermatology
%D 2014
%R 10.1155/2014/348417
%X Background. Significant decreases in p16 expression have been shown to occur in melanoma compared to Spitz tumors, and loss of p16 staining has been found to correlate with melanoma tumor progression. However, comparison of p16 between atypical cellular blue nevi (CBN) and melanoma has not been reported previously. Methods. p16 immunohistochemical staining was evaluated in 14 atypical CBN, 8 conventional and atypical melanocytic nevi, and 16 melanomas, including 4 malignant CBN. p16 staining intensity was graded on a scale of 0¨C3 and the percentage of melanocytes stained with p16 was determined. Results. p16 staining was significantly higher in all CBN as a group when compared to melanomas ( ) and malignant CBN ( ). Higher p16 expression was also seen in mildly ( ) and moderately atypical ( ), but not severely atypical, CBN compared to melanomas. Conclusions. p16 immunohistochemical expression is higher in mildly and moderately atypical CBN compared to severely atypical CBN and melanomas. In conjunction with additional markers and histology, p16 staining may be useful in confirming the benign nature of these tumors, but is not useful in distinguishing severely atypical CBN from malignant cases, consistent with the overlapping histologic features between these tumors. 1. Introduction Distinguishing atypical and unusual variants of melanocytic nevi from melanoma by routine histologic examination can be difficult in some cases [1¨C3]. In particular, differentiating atypical cellular blue nevi (CBN) from melanoma (including melanoma arising in or mimicking a cellular blue nevus, the so-called ˇ°malignant cellular blue nevusˇ±) can pose a significant diagnostic problem [1], and it has been shown that even experienced dermatopathologists often disagree in differentiating CBN, especially atypical CBN, from melanoma [4]. Like melanoma, CBN often lack maturation, can have dermal mitotic figures, extend deeply in the dermis, and may have perineural and even intralymphatic involvement [5]. Immunohistochemistry is a useful tool in the diagnosis of some cases of melanoma, and markers such as S-100, HMB-45, Melan-A, MITF, and the proliferation marker Ki-67 are often used. Ki-67, in particular, has been found useful to distinguish benign from malignant melanocytic lesions [6], but additional markers would clearly be beneficial. p16 is one of the proteins that regulates the G1/S checkpoint of the cell cycle, and it is the product of the tumor suppressor gene CDKN2 [7]. Since loss of p16 expression has been documented to occur in melanoma [8], p16 may be a potential
%U http://www.hindawi.com/journals/isrn.dermatology/2014/348417/