Background: In clinical and histopathological practice, it is sometimes difficult to distinguish pseudoepitheliomatous hyperplasia (PEH) from squamous cell carcinoma (SCC) of the skin. Several studies have shown a low density of Langerhans cells in SCC of the skin, and recent research on cervical SCCs has suggested that the decreased density of dendritic cells is secondary to low E-cadherin expression. SCCs of the head and neck similarly have decreased E-cadherin expression, but E-cadherin expression is preserved in PEH. We hypothesized that PEH of the skin would have an increased number of Langerhans cells compared with SCC.
Methods: We studied immunohistochemical expression of CD1a on paraffin-embedded tissue in 12 cases of SCC and 11 cases of PEH of the skin.
Results: The number of Langerhans cells in SCCs vs. PEH was similar; in both types of lesions, the Langerhans cells were decreased in density compared with the normal flanking epidermis.
Conclusions: PEH has a decreased number of Langerhans cells compared with the normal epidermis. As SCCs also have decreased numbers of CD1a-positive cells, this stain is not useful in differentiating these two entities.