[504] Utility of p53 Immunostaining in Inflamed Proliferative Skin Lesions.

Karl M Napekoski, Wilma Bergfeld. Cleveland Clinic, OH

Background: Immunohistochemical (IHC) staining for the p53 tumor suppressor protein has been used as an ancillary tool in distinguishing benign from malignant epithelial lesions. Literature has shown that the majority of malignant lesions show strong and diffuse p53 immunoreactivity while benign proliferative skin lesions typically show a basal/parabasal immunoreactivity. Inflamed seborrheic keratoses with reactive atypia present a diagnostic challenge as these benign lesions may have overlapping histologic features with well-differentiated squamous carcinomas. This study evaluates the utility of p53 IHC in a variety of benign and malignant proliferative skin lesions.
Design: Thirty cases were identified for study and included cases diagnosed as invasive squamous cell carcinoma (SCC) (n = 3), SCC in-situ (n = 13), inflamed seborrheic keratosis (SK) (n = 7), inflamed verruca vulgaris (n = 3), and non-inflamed verruca vulgaris (n = 4). Of note, four of the SCC in-situ lesions were arising within a SK. Immunohistochemical staining for p53 (1:20 dilution; Ventana, Tucson, AZ) was performed on all cases and the pattern of nuclear staining within the keratinocytes was recorded as either basal/parabasal or diffuse.
Results: The majority of invasive SCC (66%; 2/3) and SCC in-situ (85%; 11/13) demonstrated diffuse positivity for p53. One of the SCC in-situ lesions arising within an SK demonstrated only rare basal cell positivity. The majority of SK's (71%; 5/6) showed basal/parabasal staining; while unexpectedly a subset (29%; 2/7) of the inflamed SK's showed diffuse staining. All of the verruca vulgaris lesions, inflamed or non-inflamed, stained in a basal cell-only pattern for p53.
Conclusions: In concordance with previous literature, the majority of malignant lesions studied (invasive SCC and SCC in-situ) demonstrated a pattern of strong, diffuse positivity for p53. The basal cell-only staining of all the verruca vulgaris lesions is also in concert with previous studies. Interestingly, a minority of inflamed SK's showed a strong and diffuse pattern of p53 immunoreactivity while one SCC in-situ lesion arising within a SK had only rare basal cell positivity. These findings suggest a limitation to the utility of p53 in distinguishing benign from malignant lesions. The diffuse positivity within an inflamed SK raises the possibility that a subset may represent pre-malignant lesions.
Category: Dermatopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 115, Wednesday Afternoon


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