Pyoderma gangrenosum and pseudoepitheliomatous hyperplasia: a poorly recognized association

The histopathological distinction between florid pseudoepitheliomatous hyperplasia (PEH) and squamous cell carcinoma (SCC) is frequently difficult. Knowledge of the list of underlying conditions known to be associated with PEH and the recognition of features of such entities under the microscope are crucial to avoid a misdiagnosis of malignancy. The link between pyoderma gangrenosum (PG) and PEH is poorly understood and has been rarely mentioned in the literature. Given the lack of specific clinical and histopathological diagnostic features of PG, distinguishing PEH and SCC in epidermal proliferations associated with PG is particularly problematic. We report a case of PG of the dorsal hands which was initially mistaken for a well differentiated SCC on a skin biopsy and only correctly diagnosed on careful clinicopathological review.