A rare antenatally detected mass of the hand: tumour or congenital anomaly?

Tumour and tumour-like lesions of the hand can arise from various tissues and may present at birth. Rarely, anomalies of the hand may have an appearance mimicking a mass. We describe the imaging features of an antenatally detected floating thumb and describe its unusual mass-like appearance. While no hand tumour with similar imaging appearance has been reported, a few congenital lesions mimicking this appearance have been described. Awareness of these anomalies and identification of the typical imaging features of floating thumb allow diagnosis to be made with certainty.