Age / Sex : 40 / M

Age / Sex : 40/M

Chief complaint : A non-painful mass of the finger.

periosteal chondroma

Discussion

Findings:

Plain radiography:  Saucerization of the middle phalangeal bone of the 4^th finger at the ulnar aspect is seen. Focal bone proliferation is seen from the cortical bone. A mass density is seen contiguous to this lesion bearing stippled calcification.

MRI:  Rounded lesion with intermediate signal on T1W images, bright on T2W, definite enhancement at a inner portion of the mass.

Differential Diagnosis:

Juxtacortical chodroma, juxtacortical chondrosarcoma, florid reactive periostitis, bizarre parosteal osteochondromatosis.

Discussion:

Periosteal chondromas are benign slow growing cartilaginous tumors that arise within or beneath the periosteum and characteristically erode the adjacent cortex, as well as induce sclerosis and scalloping of the cortical surface.  Periosteal chondromas were first described as a pathologic entity in 1952.  They are relatively unusual tumors. As of 1990 only 165 cases have been reported in the world literature.  They may occur in all age groups, however most occur within the second and third decades.  Men outnumber woman in a ratio of 2:1.  The characteristic location is the metaphysis of the long bones, particularly the proximal humeral metaphysis.  Approximately 70% of cases occur within the humerus or femur, 25% of cases are within the bones of the hands and feet.  A common location is at an osseous insertion site of a tendon or ligament.  They are usually solitary, however rare reports of multiple lesions or associations with enchondromas exist.  Clinically, periosteal chondromas may present as a soft tissue mass.  Local swelling may be present as well as intermittent mild to moderate pain, which is worse with use of the affected part.  Typically there is a long history of symptoms prior to diagnosis.

Pathology:

Periosteal chondromas are composed of hyaline cartilage.  The surface may be mildly lobulated.  The tumor arises within the periosteum and erodes the adjacent cortex, and therefore resides within a cup or saucer-like crater within the cortical bone.  They are usually between 1-3 cm in diameter, and rarely larger than 4cm.  They are usually round or spherical in shape and well circumscribed.  There is no evidence of invasion of the surrounding soft tissue or the medullary bone.  The innermost margin is usually encased by a rim of endosteal lamellar bone, which separates the lesion from the medullary cavity.  Peripheral reactive new bone surrounds the lesion.  Subperiosteal new bone formation is present at the junction of tumor, bone and periosteum.  Grossly, a waxy blue-gray to white color is seen consistent with hyaline cartilage.  Microscopically, the tumor varies in cellularity.  Some features of atypia may be present suggestive of a low-grade malignancy; however mitotic figures are not seen.  Binucleate polymorphic cells are invariable.  A variable amount of calcification is present.

Imaging:

Three radiographic features associated with this lesion are described:

1) There is scalloping, "saucerization" or remodeling of the adjacent bony cortex.  The cortex is well defined and usually slightly sclerotic.  Protruding or "overhanging edges" are usually seen.  This ledge or buttress of periosteal new bone formation may extend to encase the lesion in a delicate complete or incomplete bony shell.  Therefore the lesion may occasionally, as in this case, appear totally intracortical in location without a juxtacortical soft tissue mass.

2) Lesions rarely show radiographically visible calcification.

3) The presence of a soft tissue mass should be apparent in the majority of cases.  Due to the difference in the degree of associated bony erosion and the soft tissue components, MRI has recently been found to be the most useful for delineating the relationship of the tumors to the surrounding soft tissues.  The lesions show the relatively low signal intensity of hyaline cartilage on the T1 weighted images.

Treatment:

These lesions may be removed by en bloc excision, excisional biopsy or curettage. Recurrences have been reported but are extremely rare and are probably related to inadequate surgical removal of the tumor. If a large amount of cortical bone is removed, prophylactic bone grafting is recommended.

References:

1. Abdelwahab IF et al. Case Report 588. Skel Rad 1990 19:59-61

Boriani S et al. Periosteal chondroma. A review of 20 cases. J Bone J Surg (Am) Feb 1983 65(2):205-12

2. Bauer TW et al. Periosteal Chondroma. A clinicopathologic study of 23 cases. Am J Surg Path Oct 1982 6(7):631-7

3. Lewis MM et al. Periosteal Chondromas a report of ten cases and a review of the literature. Clin Orth Rel Res Jul 1990 256:185-92

4. Resnick, D and G.Niwayama. Diagnosis of Bone and Joint Disorders, Vol 6. 1989 W.B.Saunders Philadelphia PA