[465] BD ProEx C Immunostaining in Cutaneous Melanocytic Lesions

M Li, D Frishberg, AE Walts, S Bose. Cedars-Sinai Medical Center, Los Angeles, CA

Background: ProEx C is a novel immunohistochemical marker combining antibodies against topoisomerase IIa and minichromosome maintenance protein 2 intended to detect cells with aberrant S-phase induction. Recently we reported expression of ProEx C in perineal melanomas. The purpose of our study is to evaluate the expression of ProEx C in malignant melanomas (MM), dysplastic nevi (DN) and intradermal melanocytic nevi (IDMN).
Design: Thirty cases (ten each of MM, DN and IDMN) were retrieved from our files. After H&E stained slides were reviewed and diagnoses confirmed, ProEx C and Ki-67 immunostains were performed on serial sections of a representative formalin fixed paraffin embedded block from each case with appropriate controls. Immunostains were reviewed and percent positivity recorded. Staining in 5% of lesional cells was scored as negative.
Results: Positive staining for ProEx C was seen in 7/10 (70%) of the MM (including 6/6 vertical growth phase MM and 1/3 radial growth phase MM) and 1/10 (10%) of the DN tested. Strong ProEx C positivity was observed in 15% of lesional cells in all of the positive staining MM. The one positive DN showed ProEx C staining in 10% of lesional cells. All 10 (100%) of the IDMN, 9/10 (90%) of the DN, and 3/10 (30%) of the MM (comprising 2/3 radial growth phase MM and 1/1 indeterminant growth phase MM) stained negative. In each case studied, ProEx C and Ki-67 staining was similar in pattern and distribution. In cases with 5% positivity, staining was largely confined to the junctional component. In cases with >5% positivity, staining was randomly distributed throughout the lesion.
Conclusions: Our findings suggest that a) Melanocytic lesions show differential expression with ProEx C. Most MM and one DN studied stained positive while all IDMN stained negative. b) ProEx C positivity correlates with growth phase in MM. Positive staining in 15% of lesional cells is strongly associated with vertical growth phase. c) ProEx C and Ki-67 show similar staining patterns in cutaneous melanocytic lesions. The potential of ProEx C immunostaining alone or in combination with Ki-67 to help stratify histologically similar cutaneous melanocytic lesions into prognostically different subgroups merits further study.
Category: Dermatopathology

Wednesday, March 11, 2009 9:30 AM

Poster Session V # 46, Wednesday Morning