Intraosseous lipomas: A report of six cases and a review of literature

Abstract

Background: Intraosseous lipoma is a very rare lesion, which constitutes not more than 0.1% of bone tumors. The introduction of cross-sectional imaging, especially MRI, seems to have increased the detection rate of these lesions.

Case report: The authors presented 6 cases of intraosseous lipomas in bones of the lower extremities. All lesions were detected incidentally and presented radiographically as radiolucent lesions with sclerotic borders and internal trabeculations. One lesion caused bone expansion. CT and MRI identified fatty tissue in all lesions. Cystic degeneration was present in one lesion and dystrophic calcifications in two.

Discussion: The radiographic appearance of intraosseous lipomas is not characteristic and requires differential diagnostics conducted for a long time. However, CT and MRI allow for a tissue-specific diagnosis. The detection of a predominant fatty component in a lesion confirms its benign character and no further diagnostic work-up is required.

Keywords: bone tumor; imaging; intraosseous lipoma.

Figure 1.

A 68-year-old male. (A) Plain film showing a radiolucent lesion in the proximal femoral diaphysis surrounded by a thick, irregular rim of osteosclerosis. (B) MRI. The lesion exhibiting high signal intensity on T1-weighted images, identical with the signal of subcutaneous fat.

Figure 2AB.

A 58-year-old male. (A,B) Plain films demonstrating a cystic lesion in the lateral femoral condyle and epicondyle. The eccentrically located lesion is surrounded by a sclerotic rim. It causes a moderate bone expansion, and contains internal trabeculations.

Figure 2C–E.

A 58-year-old male. MRI, T1-weighted (C), T2-weighted (D), and T2-weighted images with fat suppression (E): the signal of the peripheral part of the lesion showing the same pattern as the signal of the subcutaneous fat, whereas the central part contains fluid-filled space (low on T1, high on T2) corresponding to cystic degeneration (arrows in E).

Figure 3.

A 58-year-old female. (A) Plain AP film of both knee joints showing a cystic lesion surrounded with a thin sclerotic rim, located in the medial epicondyle of the left femur (arrows). In MRI (B) and CT (C) examinations, the lesion is composed exclusively of adipose tissue. Small foci of low signal intensity in MRI correspond to calcifications as shown by CT imaging (arrows in B and C).

Figure 4.

A 49-year-old male. AP radiogram (A) of the feet showing bilateral hallux valgus and mild osteoarthritis of tarsal joints. Lateral radiogram of the right foot (B) showing a cystic lesion in the head of the talus, surrounded by a sclerotic rim (arrows). MRI: T1- and T2-weighted images (C,D) and T2-weighted images with fat saturation (E) displaying a fatty nature of the lesion.

Figure 5.

A 28-year-old female. (A) Lateral radiogram of the foot showing a cystic lesion with a central calcification in the middle of the calcaneus (Ward’s triangle). (B) CT demonstrated a predominantly fatty content of the lesion with some soft tissue containing dystrophic calcifications in the center of the lesion.

Figure 6A,B.

A 55-year-old female with sarcoidosis. (A,B) plain AP film of the feet and lateral film of the right foot showing bilateral hallux valgus, hazy delineation of Lisfranc joints and a cystic lesion in the right cuboid bone.

Figure 6C–F.

A 55-year-old female with sarcoidosis. The lesion has a high signal intensity on T1- and T2-weighted images (C,D), which becomes attenuated on PD- and T1-weighted fat-saturated images (E,F). No contrast enhancement is observed in the lesion (F). Effusions and enhancement in the tarsal joints is due to inflammation in the course of sarcoidosis (arrows in E,F).