Granular cell tumours of the colorectum: histopathological and immunohistochemical evaluation of 30 cases.

Granular cell tumours (GCTs) are uncommon in the gastrointestinal tract, particularly in the colorectum. Herein, we report a series of 30 colorectal GCTs and discuss the properties of colorectal GCTs based on histopathological and immunohistochemical studies. Searching the surgical pathology files identified 30 cases of colorectal GCTs for 2005-2013. A broad panel of antibodies including neural and macrophage markers were used for immunohistochemical evaluation. Colorectal GCTs predominantly involved the right colon and showed increased nuclear atypia including nuclear pleomorphism and nuclear spindling. All 24 cases with mucosal tumour components had infiltrative growth patterns within the mucosa. In all available cases, diffuse strong immunopositivity was observed for S100 and SOX10 of schwannian differentiation markers, as well as for CD68. Other neuronal lineage markers, including CD56, neuron-specific enolase, nestin, and synaptophysin showed consistently high expression rates. The immunohistochemical results are suggestive for a neural origin of GCTs. Histopathological and immunohistochemical features of colorectal GCTs were delineated in this large series of 30 colorectal GCTs. Although the incidence of GCTs is relatively low, clinicians and pathologists need to be aware of GCT in the differential diagnosis.