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Age / Sex : /
Age / Sex: 64/F
Chief complaint: Palpable mass at the 4th finger
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
* Send Application Answers to Ja-Young Choi, MD (drchoi01@radiol.snu.ac.kr)
Courtesy : Sang Yong Lee, MD. Department of Radiology, Chonbuk National University Hospital
Diagnosis: BPOP, Nora's lesion(bizarre parosteal osteochondromatous proliferation)
Discussion
Findings:
1) Plain radiography Round mass, which has striated mesh-like internal densities, at the dorsal aspect of proximal interphalangeal joint of the 4th finger, left hand?
2) CT Periarticular round lesion separated from the phalangeal cortex. However at some portion round mass is connected to the phalangeal cortex. Round mass has well circumscribed maring and trabeculae-like internal densities. Round mass surround the proximal phalanx and base of middle phalanx.
Differential Diagnosis:
Osteochondroma
Myositis ossificans
Streess fracture with extensive callous formation
Diagnosis: Bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion
Discussion:
- Rare, benign lesion that was first described by Nora et al. in 1983 in the hands or feet of young adults.
- Short tubular bone involvement
- Minor trauma is an etiologic factor in the development of BPOP.
- Antecedent trauma is reported in the patient's history from 0% to 50% of cases.
- Myositis ossificans and florid reactive periostitis may progress to BPOP.
- High recurrence rate after surgical resection, up to 55% of cases
- Histologically it is composed of cartilage, bone and spindle cells. The cartilage may form a cap on the surface of the lesion, and undergoes enchondral ossification. As myositis osfficians does, with time it progresses to mature bone.
* Radiographic findings
- Dense, non-homogeneous and often multilobulated mass with a broad base attached to the bone cortex.
- Heavy mineralization with sclerotic appearance.
- Occasionaly, rapid growth and aggressive features on imaging studies.
- No cortical or permeative bone destruction.
- No continuity between mass and medullary cavity of underlying bone.
- Positive scintigraphy with an intense tracer uptake in the lesion.
* MRI features
- Useful in differentiating BPOP from several of its mimickers.
- Low signal on T1WI, high signal on STIR imaging.
-Variable signal on FSE T2 and GRE sequences, probably related to the relative amounts of cartilage present within the lesion.
References:
1. Ryu KN, Park YK, Han CS. Radiological Findings of Bizarre Parosteal Osteochondromatous Proliferation. Journal of the Korean Radiological Society 1999;41(3):571-575.
2. Shin BK, Cho HD, Yum BW, et al. Bizarre Parosteal Osteochondromatous Proliferation of the Femur (Nora’'s Lesion). J. of Korean Bone & Joint Tumor Soc 1999;5(3):178-182.
3. Ly JQ, Bui-Mansfieldb LT, Taylor DC. Radiologic demonstration of temporal development of bizarre parosteal osteochondromatous proliferation. Journal of Clinical Imaging 2004;28:216–218.
4. Sundaram M, Wang L, Rothman M, et al: Florid reactive periostitis and bizarre parosteal osteochondromatous proliferation: Pre-biopsy imaging evolution, treatment and outcome. Skeletal Radiol 2001;30:192-198.
5. Torreggiani WC, Munk PL, Al-Ismail K, et al. MR imaging features of bizzarre parosteal osteochondromatous proliferation of bone (Nora’'s lesion). Eur J Radiol 2001;40:224–231.
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