D2I2.
benign

Chondroblastoma

Chondroblastoma is a rare, , locally aggressive bone tumor that typically affects the epiphyses or apophyses of long bones. It is thought to arise from an outgrowth of immature cells (chondroblasts) from secondary ossification centers, originating from the epiphyseal plate or some remnant of it.

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Plain-language summary adapted from Wikipedia. Not medical advice.