BackgroundSquamous cell carcinoma of the lip (LSCC) and oral cavity can be life-threatening if not diagnosed early. Precancerous lesions like actinic cheilitis (AC), can transform into LSCC. Laminin is a fundamental component for basement membrane (BM) and its integrity may prevent neoplastic invasion. Therefore, laminin immunostaining of BM may be useful in identifying early invasion in actinic cheilitis and thus in the differential diagnosis between AC and invasive LSCC or high-grade epithelial dysplasia (ED).Materials and methodsBiopsies from 46 patients with oral lesions were histologically analyzed and immunohistochemically stained for laminin-1.ResultsAC was diagnosed in 34 patients and LSCC in 12 patients, including 3 patients with AC and concomitant high-grade ED/in situ carcinoma. Laminin-1 immunostaining revealed intense and linear expression of the BM in AC with low-grade ED. Loss of laminin expression was observed in LSCC. Intracellular laminin expression in parabasal cells was noted in AC with high-grade ED/in situ carcinoma.ConclusionLaminin immunostaining could be useful in identifying AC cases suspected of early invasion. It could also contribute to the histopathological differential diagnosis between AC with low- and high-grade ED and between AC and invasive LSCC. The findings of this study provide new insights into the mechanism involved in the progression process of AC into LSCC, encouraging preclinical studies that may document the stochastic role of laminin in this process.