Age / Sex : 47 / M

Chief complaint : Palpable hand mass

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Courtesy : 박찬규, Chankue Park, 양산부산대학교병원, Pusan National University Yangsan Hospital

Enchondroma protuberance

Discussion

Findings:

About 1.1 x 1.7 x 1.0cm sized exophytic mass in the right 3rd metacarpal bone.

- with intramedullary location and cortical expansion

- with lobulated shape and circumscribed margin

- with peripheral and septal enhancement

Differential Diagnosis:

Osteochondroma, Periosteal chondroma

Discussion:

Enchondroma protuberans (EP)

- rare form of enchondroma which demonstrates exophytic growth outside the margins of the bony cortex

- common site: hand (usually in the phalanges or metacarpal bones) > ribs > long bones of the arm

Radiologic findings

- Radiographs of EP typically show a well-defined geographic, osteolytic intramedullary lesion that may have poorly defined matriceal calcification combined with a cortical defect and well-defined round soft-tissue expansion. Although EP can usually be diagnosed using only radiographs, some cases could not be positively diagnosed using radiography alone because it did not reveal the protruded mass or the cortical defect. The MR images clearly delineated the connection between the intramedullary lesion and the exophytic protrusion through the cortical defect as well as the tumors themselves, which resulted in the diagnosis of EP.

Differential diagnosis

 - Osteochondroma: presence of a cartilage cap with underlying trabecular bone

 - Periosteal chondroma: periosteal location and lack of communication of the lesion with the medullary canal

Tip. Enchondroma typically appears as an intramedullary lucent lesion without mineralization at hand. However, if bone mass of the hand appears to be an exophytic mass with the characteristics of a chondroid tumor, consider enchondroma protuberans.

References:

HS Kang, JM Ahn, Y Kang. Oncologic imaging: Bone tumors. Springer. 2017

A Kord, B Kravis, S Rsotami. Enchondroma protuberans of the hand: A case report. Radiology case report. 2020 15(7):943-946

An YY, Kim JY, Ahn MI. Enchondroma Protuberans of the hand. Am J Roentgenol. 2008 190(1):40-4.