Keywords
metachronous - osteoid osteoma - fibula - humerus
Introduction
Osteoid osteomas are almost always solitary, with multiple tumors occurring in the
same patient in less than 1% of reported cases.[1]
[2] Where multi focal tumors are encountered, they are typically found in the same bone[1] with up to 60% of cases being identified in the proximal femur and mid-diaphysis
of the tibia.[3] The second commonest site is in the spine where up to 20% of cases occur, particularly
in the posterior elements.[4] We report a rare case of metachronous osteoid osteoma of the mid-diaphysis of the
right fibula followed by right distal humerus osteoid osteoma after a 7-year disease-free
interval.
Discussion and Conclusion
Osteoid osteoma is an uncommon neoplasm of the bone accounting for ∼10% of benign
bone tumors.[5] It was first described by Jaffe in 1935.[6] Patients classically present with persistent dull achy pain worse during the night
relieved with aspirin or nonsteroidal anti-inflammatory drugs. It is most commonly
seen in adolescents and young adults in a 2:1 male to female ratio.[7] The treatment of symptomatic osteoid osteoma usually involves radio frequency ablation
or curettage.
The classic radiological appearances of osteoid osteoma are of a radiolucent oval
central focus with a size of smaller than 1 cm with surrounding reactive sclerosis.[8] CT may show a well-defined nidus of low attenuation, but higher attenuation may
be seen in cases where the nidus is mineralized.[8] MRI demonstrates the nidus with marked perilesional osseous and soft tissue edema
and surrounding sclerosis.[9] A joint effusion and synovitis may also be seen.
The occurrence of multiple osteoid osteomas is rare. The majority of cases were found
to be localized to the same region/bone.[10] Schai et al reported a case of multifocal osteoid osteoma with one focus in the
cancellous region of the greater tuberosity of the humerus and a second cortical focus
at the proximal humerus diaphysis.[2] In very rare cases, multiple synchronous tumors may be found in adjacent bones and
to a lesser extent in remote bones.[11] Beck et al reported a metachronous osteoid osteoma of the tibia and the T7 vertebral
body, while Giuseppe et al described a case of osteoid osteoma of the right distal
femur with a history of previous osteoid osteoma in the left distal femur.[11]
[12] In our patient, the lesions were found to be anatomically distant and were separated
by a 7-year interval. It is possible that this occurrence represents nothing more
than a mere coincidence; however, it is also possible that a metachronous presentation
of these tumors reflects a genetic predisposition.
Our case indicates that a second osteoid osteoma may occur in a different bone in
the same patient even after many years. Therefore, in the case of a patient with previous
history of OO presenting with typical signs and symptoms of osteoid osteoma such as
deep and persistent pain at a different site, worsening at night, and relieved by
salicylates, it is important to include a metachronous osteoid osteoma as part of
the differential diagnosis.
