Osteoblastoma of the thumb with a novel PRSS44::ALK fusion and literature review of osteoblastoma of hands and feet bones

Abstract

Osteoblastomas (OBs) are benign neoplasms constituting approximately 1% of primary bone tumors with a predilection for the spine and sacrum. We describe an OB of the proximal phalanx of the left thumb in a 38‐year‐old female. MRI of left hand demonstrated a 29‐mm mildly expansile enhancing lesion involving the entire proximal phalanx of the first digit. Histology displayed a bone‐forming tumor consisting of trabeculae of remodeled woven bone framed by plump osteoblasts in a vascularized background. Next‐generation sequencing analysis identified a PRSS44::ALK fusion gene.