Novel case of a granular cell tumour mimicking breast malignancy and a metachronous axillary skin lesion

A 51-year-old woman presented with an asymptomatic screen-detected lesion of the right breast. The core biopsy showed a granular cell tumour (GCT). Twelve months later the woman presented with an incidental finding of a skin lesion in the left axillary fold during her annual breast surveillance review. Histopathology confirmed a second metachronous GCT. GCTs are an uncommon benign tumour of Schwann cell origin that can infrequently be multifocal. Due to the non-specific clinical presentation and radiological features, the gold standard of diagnosis relies on histologic assessment. We describe a novel case of metachronous GCT within the breast tissue mimicking a breast malignancy as a mammography screen-detected lesion, followed by a second GCT mimicking a scar lesion on the contralateral axillary fold.