Distinguishing between irritated seborrheic keratosis and squamous cell carcinoma in situ using BCL-2 and IMP3 immunohistochemistry.

ABSTRACT

BACKGROUND: Distinguishing an irritated seborrheic keratosis (ISK) from a squamous cell carcinoma in situ (SCCIS) can occasionally be challenging, both histologically and clinically. The purpose of this study was to determine if an immunohistochemical profile of select markers can aid in differentiating these two entities. METHODS: We randomly selected and stained 103 ISK and 111 SCCIS for EGFR, IMP3, and BCL-2. IMP3 staining was scored as negative or 0 (0% positive), 1+ (1%-25% positive), 2+ (26%-50% positive), and 3+ (>50% positive). BCL-2 and EGFR were graded as either positive or negative. RESULTS: Sixty five out of 103 (63%) ISKs were positive for BCL-2, none (0%) were positive for IMP3, and 18 (18%) were positive for EGFR. Fifteen out of 111 (14%) SCCISs were positive for BCL-2, 26 (23%) were positive for IMP3, and 27 (24%) were positive for EGFR. BCL-2 was moderately sensitive (63%) and specific (87%) in identifying ISK. IMP3 was specific (100%) but not sensitive (23%) for SCCIS. CONCLUSION: Our findings indicate that the combination of IMP3 and BCL-2 may be of diagnostic utility in distinguishing between ISK and SCCIS in daily clinical practice. EGFR immunohistochemistry did not appear to be useful in this setting.