Background: An extraskeletal chondroma is a benign soft tissue tumor but occasionally atypical morphologic features create difficulties for differential diagnosis from malignancy.Case Report: A gradually enlarging tumor was removed from the left palm of a 61-year-old female patient. Histological images showed an extremely rare case of extraskeletal chondroma with proliferating large chondroblast-like cells,containing both atypical cells and karyomitosis. Eleven years after the surgery, there was no sign of a local recurrence or metastasis.Conclusions: Careful diagnosis of this type of extraskeletal chondroma is required to avoid overtreatment due to incorrect diagnosis.

Keywords: extraskeletal chondroma, chondroblast-like cell, Hand, long-term follow-up