General Approach to Lytic Bone Lesions

D. Lee Bennett, MD, MA; Georges Y. El-Khoury, MD

Disclosures

Appl Radiol. 2004;33(5) 

In This Article

Differential Diagnosis

One of the most important first steps in deriving a differential diagnosis when evaluating a lytic lesion is to know the age of the patient. This is an important piece of information in musculoskel-etal radiology. Typically, only certain lesions occur within any given age range; therefore, the age of the patient must be considered in order to generate a correct differential diagnosis. Some of the lytic lesions that are largely confined to certain age groups are: metastatic neuroblastoma in the infant and young child, metastasis and multiple myeloma in the middle-aged and elderly, Ewing's sarcoma and simple bone cyst in the long bones in children and young teenagers, and giant cell tumor in the young to middle-aged adult (20 to 50 years of age).[3,4]

The next step is to examine the lesion to see if it has a pathognomonic appearance and/or location. Some lytic lesions have a characteristic radiographic appearance (including matrix) and/or location that are inherently diagnostic. A few examples include: a corduroy vertebral body (hemangioma; Figure 3), a fallen fragment sign (simple bone cyst; Figure 4), intralesional gas in a juxta-articular lesion (subchondral cyst, such as a degenerative cyst or intraosseous ganglion cyst; Figure 5), an enlarged bone with coarsened trabeculae and a thickened cortex (Paget's disease; Figure 6), chondroid matrix in a geographic lytic lesion in the hand (enchondroma; Figure 7), vertebra plana in an otherwise healthy child (Langerhan's cell histiocytosis; Figure 8), and the cockade sign in the calcaneus (intraosseous lipoma; Figure 9). One must become familiar with characteristic pathognomonic radiographic signs and appearances of lytic lesions.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 3.

Vertebral body hemangioma in a 48-year-old woman. (A) The vertically oriented, thickened trabeculae (corduroy sign) of a vertebral body hemangioma can be seen on this lateral view, which is coned down to the L2 vertebral body. (B) T1- weighted and (C) T2-weighted MR images show the typical increased signal intensity of a vertebral body hemangioma (arrows). (D) This axial CT image of the L2 vertebral body illustrates the classic dot appearance to the trabecular bone found in vertebral body hemangiomas.

Figure 4.

Simple bone cyst in an 8-year-old child. This anteroposterior radiograph of the proximal humerus shows the fallen fragment sign (arrow) of a simple bone cyst.

Figure 5.

Intraosseous ganglion cyst in a 16-year-old. This axial CT image shows intralesional gas (arrow), which confirms the diagnosis of an intraosseous ganglion cyst in this otherwise healthy patient.

Figure 6.

Paget's disease involving the calcaneus in a 50-year-old man. (A) This lateral radiograph of the ankle readily shows the classic Paget's disease findings of an enlarged bone, coarsened trabeculae (arrows), and thickened cortex (arrowheads). (B) This coronal T1-weighted MR image of the calcaneus also shows the coarsened trabeculae (arrow) and thickened cortex (arrowheads) of Paget's disease. In the peripheral skeleton, bone involved with Paget's disease should have normal marrow signal interspersed between the coarsened trabeculae.

Figure 6.

Paget's disease involving the calcaneus in a 50-year-old man. (A) This lateral radiograph of the ankle readily shows the classic Paget's disease findings of an enlarged bone, coarsened trabeculae (arrows), and thickened cortex (arrowheads). (B) This coronal T1-weighted MR image of the calcaneus also shows the coarsened trabeculae (arrow) and thickened cortex (arrowheads) of Paget's disease. In the peripheral skeleton, bone involved with Paget's disease should have normal marrow signal interspersed between the coarsened trabeculae.

In regard to matrix, mineralization of both chondroid and osteoid matrix can be visible on radiographs. Mineralization of chondroid matrix is seen as dot-like, popcorn-like, arcs and rings of calcifications within the bone tumor, while osteoid matrix has a cloud-like, wispy appearance (Figures 10 and 11). Some lesions that can have radiographically visible chondroid matrix include enchondroma, chondroblastoma, and chondrosarcoma. Osteoid matrix can be seen in osteosarcoma and osteoid osteoma/osteoblastoma.[5]

Figure 6.

Paget's disease involving the calcaneus in a 50-year-old man. (A) This lateral radiograph of the ankle readily shows the classic Paget's disease findings of an enlarged bone, coarsened trabeculae (arrows), and thickened cortex (arrowheads). (B) This coronal T1-weighted MR image of the calcaneus also shows the coarsened trabeculae (arrow) and thickened cortex (arrowheads) of Paget's disease. In the peripheral skeleton, bone involved with Paget's disease should have normal marrow signal interspersed between the coarsened trabeculae.

Figure 7.

Enchondroma of the proximal phalanx in a 57-yearold woman. The pathognomonic findings of a lytic geographic lesion with expansion and chondroid matrix (arrows) are seen on this radiograph of the proximal phalanx of the index finger.

If the appearance of the lytic lesion is not pathognomonic, such that one cannot give a definitive diagnosis or a succinct differential diagnosis, then the radiologist must determine the aggressiveness of the lesion. Generally speaking, benign lesions can have a quiescent or aggressive appearance, while malignant lesions have an aggressive appearance. Two radiographic characteristics we have found useful in determining the aggressiveness of a lytic lesion are the appearance of the lesion based on the Lodwick classification system and the type of periosteal reaction present.

The authors use the revised Lodwick classification system when evaluating the appearance of a lytic lesion because this has been shown to be a reliable and accurate method of determining that certain lesions have a very high likelihood of not being malignant based on their radiographic appearance.[6,7] This is a fairly versatile classification system in that multiple factors important in evaluating lytic bone tumors can be incorporated into a single grading system. The factors incorporated into the revised Lodwick classification system include soft-tissue involvement, pattern of bone destruction, size of lesion, zone of transition, margin sclerosis, and host response.

The revised Lodwick classification system consists of five grades labeled IA, IB, IC, II, and III. The grading of a lesion is performed in a sequential four-step manner.

The first step is to determine the type of bone destruction present in the lesion. A lesion with geographic destruction would be defined as a lesion having a sharp, clearly defined margin (grade I; Figure 12). Moth-eaten destruction is similar to moth-eaten clothes with holes of destroyed bone. Permeative destruction is an ill-defined, diffuse, somewhat subtle destructive process of bone. Those lytic lesions that are entirely moth-eaten and/or permeative are grade III (Figure 13). Any lytic lesion that is a combination of geographic with moth-eaten and/or permeative destruction is a grade II lesion (Figure 14). If the lesion is grade II or III, then that lesion is classified and is considered malignant until proven otherwise. If the lesion is grade I, then classification proceeds to the second step. Lodwick often found it difficult to differentiate between grade II and III lesions, but it does not really matter because both grades indicate an aggressive lesion that needs further evaluation and/or treatment.

Figure 8.

Langerhan's cell histiocytosis involving the spine in an 8-year-old boy. In this otherwise healthy child, vertebra plana can be seen (arrow) in the thoracic spine, which is consistent with Langerhan's cell histiocytosis.

Figure 9.

Intraosseous lipoma of the calcaneus in a 35-year-old man. (A) This lateral radiograph of the ankle shows a geographic lytic lesion in the calcaneus. Dystrophic calcifications, known as the cockade sign, can be seen within the lesion (arrow). This is a classic pathognomonic appearance and location of an intraosseous lipoma. Parasagittal (B) T1- weighted and (C) Short tau inversion recovery (STIR) MR images, respectively, show signal characteristics (hyperintense on T1 and hypointense on STIR) that are consistent with a fatcontaining lesion (intraosseous lipoma). Signal arising from the dystrophic calcifications can also be seen within the lesion (arrows).

Figure 9.

Intraosseous lipoma of the calcaneus in a 35-year-old man. (A) This lateral radiograph of the ankle shows a geographic lytic lesion in the calcaneus. Dystrophic calcifications, known as the cockade sign, can be seen within the lesion (arrow). This is a classic pathognomonic appearance and location of an intraosseous lipoma. Parasagittal (B) T1- weighted and (C) Short tau inversion recovery (STIR) MR images, respectively, show signal characteristics (hyperintense on T1 and hypointense on STIR) that are consistent with a fatcontaining lesion (intraosseous lipoma). Signal arising from the dystrophic calcifications can also be seen within the lesion (arrows).

Figure 9.

Intraosseous lipoma of the calcaneus in a 35-year-old man. (A) This lateral radiograph of the ankle shows a geographic lytic lesion in the calcaneus. Dystrophic calcifications, known as the cockade sign, can be seen within the lesion (arrow). This is a classic pathognomonic appearance and location of an intraosseous lipoma. Parasagittal (B) T1- weighted and (C) Short tau inversion recovery (STIR) MR images, respectively, show signal characteristics (hyperintense on T1 and hypointense on STIR) that are consistent with a fatcontaining lesion (intraosseous lipoma). Signal arising from the dystrophic calcifications can also be seen within the lesion (arrows).

The second step is to re-evaluate the margin of the lesion, including any cortex that the lesion abuts. If any of the margins are indistinct, then the lesion is classified as grade IC (Figure 15). Margins that are indistinct should not be confused with moth-eaten/permeative destruction (grade II or III). If the lesion cannot be classified as grade IC, then classification proceeds to the third step.

Figure 9.

Intraosseous lipoma of the calcaneus in a 35-year-old man. (A) This lateral radiograph of the ankle shows a geographic lytic lesion in the calcaneus. Dystrophic calcifications, known as the cockade sign, can be seen within the lesion (arrow). This is a classic pathognomonic appearance and location of an intraosseous lipoma. Parasagittal (B) T1- weighted and (C) Short tau inversion recovery (STIR) MR images, respectively, show signal characteristics (hyperintense on T1 and hypointense on STIR) that are consistent with a fatcontaining lesion (intraosseous lipoma). Signal arising from the dystrophic calcifications can also be seen within the lesion (arrows).

In the third step, the lesion is evaluated for expansion. If an expanded cortical shell is present and it exceeds 1 cm, then the lesion is classified as grade IB (Figure 16). The fourth step consists of evaluating the lesion for the presence of a circumferential sclerotic margin. If the lesion has a sclerotic margin, it is classified as grade IA (Figure 12). Those with a nonsclerotic margin are classified as grade IB.

Figure 10.

Enchondroma of the distal femur in a 45-year-old woman. This anteroposterior radiograph of the distal femur readily shows the coarse dot-like, popcorn-like mineralization of chondroid matrix.

Usually, the authors recommend follow-up imaging for lytic lesions that are asymptomatic, have a grade IA appearance, and are found in an otherwise healthy patient. Nonspecific and nonpathognomonic lytic lesions that are grade IB, IC, II, III, or are symptomatic warrant further work-up at the time of discovery. Based on previous studies, the likelihood of malignancy using the revised Lodwick classification (disregarding patient symptoms and whether the lesion is pathognomonic in appearance) is as follows: grade IA is 6%, grade IB is 48%, grade IC is 36%, grade II is 97%, and grade III is 100%.[6,7] If pathognomonic lesions are excluded from the results of these studies, the likelihood of malignancy of grade IA lesions falls to 2% to 4%.

If periosteal reaction is present, we classify it as either solid or interrupted ( Table 1 ).[8] Solid periosteal reaction is described as a single layer of new bone thicker than 1 mm and uninterrupted throughout its extent. Interrupted periosteal reaction is simply the laying down of new bone that is interrupted -- that is, not continuous or solid. Some examples include sunburst and Codman's triangle. Interrupted periosteal reaction indicates that the associated lesion is aggressive.[8] Those lesions that are not pathognomonic in appearance and have an interrupted periosteal reaction also warrant further work-up because of their higher likelihood of malignancy.[8] It is important to remember that interrupted periosteal reaction is sometimes seen with osteomyelitis.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....