Vascular invasion and other invasive features in granular cell tumours of the skin: a multicentre study of 119 cases

Background Incidental finding of vascular invasion has been described in some benign granular cell tumours. Malignancy in granular cell tumours is excessively rare and its assessment relies on necrosis and cytological criteria. Aims To assess histopathological invasive features, particularly vascular invasion, in a large series of granular cell tumours of the skin. Methods 119 granular cell tumours of the skin were collected in 114 patients between 2001 and 2011. Histopathological and epidemiological data were collected. Five step sections and one orcein staining were performed in all cases. Results Mean age of the patients was 43.7 +/- 18 years. Granular cell tumours were multiple in 7% of patients. They were classified as benign in 111 cases, and atypical in eight cases. No malignant granular cell tumour was present. Tumours had 1.48 +/- 1.3 cm mean diameter, showed peripheral invasive growth pattern in 71% of cases, had a mean depth of 8.8 +/- 4.7 mm, and reached the subcutis in 66% of cases. Infiltration of arrector pili muscle occurred in 23% (95% CI 16% to 32%), and perineural spread in 66% (95% CI 56% to 74%) of cases. Vascular invasion occurred in 23% (95% CI 16% to 32%) of cases, with subendothelial layers infiltration or vascular obliteration. No intraluminal embolus was found. No association was found between vascular invasion and clinical outcome. Conclusions Histopathological features of local invasion are frequent in otherwise benign granular cell tumours. Vascular invasion consists of an infiltration of the subendothelial layers, without intraluminal cells, and may not be considered as a marker of adverse prognosis.