Morphometrical differences between pseudo-epitheliomatous hyperplasia in granular cell tumours and squamous cell carcinomas

Aim: Granular cell tumour (GCT) is a benign tumour which occasionally induces pseudo-epitheliomatous hyperplasia (PEH) of the covering epithelium, mimicking squamous cell carcinoma (SCC) invasion. PEH cells do not show marked atypia, but the presence of pseudoinvasive patterns remains a diagnostic problem since several misdiagnosed cases have been reported. This study investigated objective morphometric criteria to distinguish GCT-PEH from SCC. Methods and results: The complexity of the epithelial connective tissue interface (ECTI) in 57 profiles from nine SCC and 12 GCT-PEH cases was analysed using fractal geometry. Epithelial and non-epithelial cells were segmented using a space partition procedure and analysed morphometrically. GCT ECTI profiles were significantly more complex than those of SCC. The complexity of ECTI quantified by global and local fractal dimensions allowed up to 86% correct discrimination between GCT-PEH and SCC. The cell-wise discrimination between the two entities using cellular morphology was 76% but when the two approaches were combined, the correct discrimination was 96%. Conclusions: The architectural features of GCT-PEH and SCC show differences which, when quantified, could be used to differentiate the two diagnostic classes. Characterization of these differences may help to elucidate some of the mechanisms of tumour infiltration and metastasis.