Clin Orthop Surg.  2015 Jun;7(2):264-268. 10.4055/cios.2015.7.2.264.

Osteochondrolipoma Presenting as a Popliteal Cyst

• Choi YJ
• Kang JH
• Kang GH
• Choi SJ

• KMID: 2164555
• DOI: http://doi.org/10.4055/cios.2015.7.2.264

Abstract

Here, we describe a popliteal mass that was initially misdiagnosed as a simple popliteal cyst, which finally turned out to be osteochondrolipoma. A 63-year-old housewife presented with sustained knee pain in association with a palpable mass on the popliteal fossa. The mass was in the posteromedial area and soft, non-tender, non-movable in the posteromedial area. Using plain radiography, the mass appeared as a round, soft tissue density lesion containing bony fragments. We performed an ultrasound-guided needle biopsy in conjunction with magnetic resonance imaging, followed by an open excisional biopsy. Microscopically, histological sections showed a lipoma with cartilaginous and osseous differentiation, finally diagnosed as osteochondrolipoma. In conclusion, popliteal masses are not always simple cysts, and the evaluation of masses in the popliteal fossa is always necessary.

Keyword

Popliteal cyst; Neoplasm; Biopsy

MeSH Terms

Female
Humans
Lipoma/complications/*diagnosis
Middle Aged
Osteochondroma/complications/*diagnosis
Popliteal Cyst/etiology
Soft Tissue Neoplasms/complications/*diagnosis

Figure

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  Fig. 1 The plain radiograph of the left knee shows a mass-like lesion containing fat (long arrow) and internal ossifications (short arrows) in the posterior area of the left knee.

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  Fig. 2 The ultrasound (US) scan of US-guided biopsy reveals a well-defined soft tissue mass and prominent acoustic shadowing caused by internal ossifications.

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  Fig. 3 Sagittal plane magnetic resonance imaging scans: (A) T1-weighted image, (B) T2-weighted image, (C) fat-suppressed gadolinium-enhanced image, and (D) axial T1-weighted image. The contents of the mass are presumed to be fat (arrows), enhancing fibrous tissue (arrow heads), and ossifications. The tibial nerve (curved arrow) is shown separately.

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  Fig. 4 Photograph of the popliteal mass. The mass is well-circumscribed and the cut surface is yellow and fatty with traversing whitish fibro-chondroid bands and nodules.

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  Fig. 5 Histological sections of the tumor specimen show lipoma with cartilaginous and osseous differentiation. (A) Ossification in the chondroid nodule. Lamellar bone with osteoblasts and osteoclasts is being formed in the chondroid nodule (H&E, ×40). (B) Fibroblast proliferation and fibrous band is intimately apposed to the fat necrosis area of lipoma (H&E, ×100). (C) A chondroid nodule in the lipoma. Chondroid matrix and chondrocytes are arising in the fibromyxoid band (H&E, ×40).

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