Expression of laminin-5 γ2 chain in cutaneous pseudocarcinomatous hyperplasia

Since the use of laminin-5 as a marker of invasiveness has been proposed by several authors, our objective was to compare the expression of this protein in pseudocarcinomatous hyperplasia and squamous cell carcinoma (SCC).

Sixty-four paraffin-embedded skin biopsy samples with diagnosis of epidermal hyperplasia (non-pseudocarcinomatous), pseudocarcinomatous hyperplasia, actinic keratosis/carcinoma in situ, microinvasive and frankly invasive SCC were obtained for immunohistochemical study.

Adjacent normal epithelium and epidermal hyperplasia (non-pseudocarcinomatous) showed no staining. In pseudocarcinomatous hyperplasia, laminin-5 was positive, at least focally, in 14 of 16 (87.5%) samples and was concentrated in peripheral cells of elongated rete pegs and in migrating cells in dermis. In samples of microinvasive carcinoma (n = 7), the expression was observed in all cases and was concentrated in the leading edge of the tumor. All cases (n = 21) of frankly invasive SCC showed cells expressing laminin-5, at least focally. Well-differentiated areas of the tumor presented a pattern of expression in peripheral cells of tumor nests while a diffuse pattern of expression was observed in less differentiated areas.

We showed that cytoplasmic laminin-5 expression should not be used as a criterion of malignancy and is not useful in distinguishing pseudocarcinomatous hyperplasia from microinvasive and well-differentiated SCC.