Peritumoral matrilin‐2 staining may be useful in distinguishing basal cell carcinoma from folliculocentric basaloid proliferation

Background Folliculocentric basaloid proliferation (FBP) is a benign and reactive proliferation which can histopathologically mimic basal cell carcinomas (BCCs). The incidental presence of FBP during the excision of a BCC can occasionally lead to excessive tissue removal. One distinguishing feature of BCCs is that they invade the stroma, whereas FBPs generally do not. Methods Matrilin‐2 is an extracellular matrix protein associated with tumor invasion, and we compared the expression of matrilin‐2 in peritumoral cells of BCC and FBP. Results We found increased matrilin‐2 expression within the peritumoral stroma of 41 of 42 BCCs (97.7%), with strong expression in all (100%) cases of infiltrative subtypes and in 21 of 25 (84%) nodular subtypes of BCC. We found no expression of peritumoral matrilin‐2 in any of the seven cases of FBP. Conclusion Our results suggest that immunolabeling with the matrilin‐2 antibody may help distinguish BCCs from FBPs.