The purpose of this study was to achieve better understanding of extraskeletal myxoid chondrosarcoma (EMC). 13 cases of EMC confirmed by surgery biopsy were retrospectively studied. All patients underwent preoperative CT or/and MRI examinations. Among six patients who underwent preoperative CT examinations, six cases of lesions exhibited hypodensity on unenhanced image, three cases of tumor showed funicular spots or patchy calcification, and four cases of tumor did not show any obvious enhancement after enhanced CT scan. Among ten patients who underwent preoperative MRI examination, 8 cases of tumor revealed uniform or slight hyposignal intensity on T1WI, 10 cases of tumor demonstrated lobulated hypersignal intensity with multiple low signal intensity of interval septa on T2WI, and 5 cases of lesions indicated characteristic appearance: septa enhancement with tumor stroma between interval septa being unenhanced. EMC usually occurred at older men and at certain location such as limbs, trunk, and subcutaneous tissues. EMC usually exhibited low density mass (mostly 20-40HU) with calcification and in a portion of the cases showed light or no enhancement on CT. On MRI, EMC showed lobulated hypersignal intensity on T2WI with characteristic arc, septa, or interval septa enhancement.
Extraskeletal myxoid chondrosarcoma (EMC) is a rare low-grade malignant mesenchymal neoplasm of uncertain differentiation characterized by abundant myxoid matrix located in the soft tissues. It affects mainly the soft tissues of the proximal end of long bones. Its incidence in the head and neck region is less than 5% [
EMC demonstrate a strong tendency for local recurrence (37- 48%) and metastatic disease (50%), usually pulmonary [
Studies in the past were aimed at improving disease control in the surgical resection, radiotherapy, with some reported benefit from tyrosine kinase inhibitor sunitinib malate in the metastatic setting [
In this article, we reported CT and MRI studies of 13 cases of EMC with corresponding pathological analyses. The purpose of this study was to achieve better understanding of EMC by describing its radiological and pathological characteristics. To our knowledge, this is the largest cohort of patients with EMC imaging characteristics that has been analyzed to date.
A total of 13 EMC cases were obtained from April 2005 to March 2017 at two hospitals, including our own. All cases were clinically diagnosed and went through surgical procedures, pathological analyses, and postsurgical follow-up in our hospital.
Computer tomography (CT) exams were performed in 7 cases before surgery. Dual energy CT (Siemens SOMATOM Definition) images were acquired with the following parameters: slice thickness 5-10 mm, tube voltage 120 kV, tube current 559 mA, pitch 3.2, gantry perpendicular to the CT table. Multiplanar reformatting of CT images was performed on a workstation (Advantage Workstation 4.3; GE Healthcare, Waukesha, WI, USA).
Magnetic resonance imaging (MRI) with and without contrast was performed in ten cases on a 3.0T MRI scanner (GE Signa Excite). Dedicated coils were used for imaging different body areas and the regions of interest. MR images were acquired using spin echo sequences—axial view: T1WI: TR/TE 440/8.2 ms, T2WI: TR/TE: 4000/142.5 ms, slice thickness: 5mm, NEX:4.0, FOV: 38cm×38cm, and matrix: 256×224~512×446. Fat-suppressed T1-weighted transverse images: the gadopentetate dimeglumine (Magnevist, Schering, Berlin, Germany) was intravenously injected. The dose was 0.1mmol/kg per patient and the injection rate was 2.0 ml/s—axial view: T1WI: TR/TE 560/8.0 ms, slice thickness: 6mm, FOV: 38cm×38cm, and matrix: 320×192~512×446; corona view: T1WI: TR/TE 560/8.2 ms, slice thickness: 5mm, FOV: 40cm×40cm, and matrix: 320×192~512×446.
All images were analyzed by two board-certified radiologists, who specialize in musculoskeletal imaging. On CT images, tumor location, morphology, size, edge, density, and the presence of calcification of the tumor were evaluated. On MR images, tumor morphology, edge, signal intensity and enhancement, necrosis, hemorrhage, and peritumoral edema were evaluated. All imaging findings were correlated with pathological analyses.
Tumor specimens obtained after surgical resection were fixed in 10% formaldehyde solution for 24 hours for dehydration, and the paraffin-embedded specimens were sliced and stained with hematoxylin and eosin (H&E). Immunohistochemistry: streptavidin-peroxidase-biotin (S-P) link staining with 3,3'-diaminobenzidine (DAB) color rendering was performed on some specimens. Cytoplasmic brown precipitate was considered to be positive. Histopathological characteristics were evaluated by a board-certified pathologist specializing in musculoskeletal specialty.
A total of 13 cases (6 males and 7 females) were collected, with ages ranging from 28 to 65 years with an average age of 41.9 years. The locations of EMC in each patient are listed in Table
The clinical and imaging manifestations of EMC.
No | Age | Sex | location | Medical history | size (cm) | Manifestation of CT | CT value (Hu) | CT enhancement | T1WI | T2WI | Internal mass |
---|---|---|---|---|---|---|---|---|---|---|---|
1 | 52 | M | Right gluteal | 20+ days | 7.5x7 | / | / | / | Slight low signal | Strongly high signal, lobulated | Enhancing internal septation |
2 | 55 | F | Left thigh | 1 year | 1.6x2.2 | Low density, round mass | 15-25 | Minimal (<10Hu) | / | / | / |
3 | 40 | M | Right thigh | 6 years | 7.5x7.1 | / | / | / | Iso signal, with dark internal septation | Strongly high signal, lobulated | Enhancing internal septation |
4 | 44 | F | lower abdomen | 1 year | 8.9x8.5 | Isodensity, lobular mass, with calcification | 37-40 | Moderate enhancement, heterogeneous | Iso signal, with dark internal septation | Strongly high signal, lobulated | Enhancing internal septation |
5 | 43 | F | Spinal canal | 3 years after operation | 1.1x1.5 | / | / | / | Slight high signal | Iso signal | Heterogeneous |
6 | 54 | M | Right pars nasalis pharyngis | 20 days | 4.0x2.7 | Isodensity, irregular mass | 24-38 | Minimal (<10Hu) | / | / | / |
7 | 65 | M | Right carpal canal | 8 years | 1.5x1.8 | / | / | / | Iso signal | high signal, with dark internal septation | / |
8 | 47 | M | Left buttocks | 5 years | 8x6 | / | / | / | Iso signal, with dark internal septation | Strongly high signal, lobulated | Enhancing internal septation |
9 | 45 | F | Right knee | 1 week | 8.0x6.6 | Low density, irregular mass | 23-28 | / | Iso signal, with dark internal septation | Strongly high signal, lobulated | Enhancing internal septation |
10 | 48 | F | Walls of the chest | 3 years | 3.2x4.1 | Low density, irregular mass | 16-20 | Minimal (<10Hu) | / | / | / |
11 | 28 | F | Right lower jaw | 1 month | 4.6x3.7 | / | / | / | Slight low signal | High signal | Heterogeneous |
12 | 43 | M | Right lower limb, pelvis | 3 years | 12x10 | Uneven density, irregular mass, with calcification | / | Moderate (>20Hu) | Mixed signal | Strongly high signal, lobulated | Rim enhancement |
13 | 33 | F | Right lumbosacral portion | 2 months | 4.5x2.5 | Uneven density, irregular mass | / | Minimal (<10Hu) | Slight low signal | Strongly high signal, lobulated | / |
CT findings of all cases are listed in Table
MRI findings of all cases are listed in Table
Images obtained from a 52-year-old man with EMC of the right gluteus. (a-b) T1WI and T2WI: the lesion (red arrow) demonstrated lobulated mass with hyposignal intensity on T1-weighted sequences and hypersignal intensity on T2-weighted sequences; it showed enhancing internal septation after injection of gadolinium (c).
Images obtained from a 55-year-old woman with EMC of the left thigh. (a, b) Transverse CT scan showed low density, round mass without marked enhancement (white arrow).
Typical radiological appearance from a 40-year-old man with EMC of the right thigh. An irregular-shaped soft tissue mass in right thigh with long T1 and T2 was observed (a, b). An enhanced MRI scan revealed an obvious uneven enhanced mass with radiated arrangement separation enhanced like spokes (c).
A 44-year-old woman with extraskeletal myxoid chondrosarcoma of the lower abdomen (red arrow). Transverse CT scan showed low density, irregular mass with spot-like calcification (a). Axial contrast-enhanced CT shows that this mass is with moderate enhancement (b). The lesion exhibited hypersignal intensity on T2-weighted sequences (c) and heterogeneous enhancement after injection of gadolinium (d).
Images obtained from a 43-year-old woman with EMC of the spinal canal (red circle). MRI showed a mass in the spinal canal with both slight high signal on T1WI and T2WI (a, b). Gadolinium-enhanced T1-weighted fat-suppression images showed heterogeneous enhancement (c).
Typical radiological appearance from a 48-year-old man with EMC of the walls of the chest. Transverse CT scan showed low density, irregular mass ((a), CT value=16.2Hu) without marked enhancement ((b), CT value=19Hu in CT Contrast Enhancement).
Imaging features (yellow arrow) from a 28-year-old woman of the right lower jaw. (a) T1-weighted MRI shows a uniform low signal mass. (b) T2-weighted MRI shows a heterogeneous high signal mass. (c) Gadolinium-enhanced T1-weighted fat-suppression images showed heterogeneous enhancement.
During surgical procedures, tumors showed a lobulated appearance with complete pseudocapsules. The gross specimen sections were composed of a plurality of jelly-like tumor nodules, separated by fibrous tissues between the nodules, partially exhibiting cystic degeneration, hemorrhage, and necrosis. Under optical microscope, numerous lobes were seen in the tumor, and the lobes were filled with mucinous stroma or cartilage myxoid stroma. Also a large number of tumor cells in the shape of a short spindle or circle that were distributed around the tumor periphery were observed. A small amount of tumor cells was embedded in the mucinous stroma, which was plentiful in the central region. In rare cases, tumor cells lost their self-adhesion and became distributed throughout the mucinous stroma.
In 9 out of 13 cases, the patients had clinical follow-up within 10-33 months. Five of those patients have had no recurrence to date. Four of those patients had recurrent tumors in the original site within 5-19 months, and one patient had another recurrence after the second surgery. One patient died due to lung metastases.
EMC was first described by Stout et al. in 1953 [
Recent statistics show that EMC cases have a high rate of local recurrence, metastasis, and patient mortality rate [
Our data shows that the average age of onset of the EMC patients was about 41.9 years. In six cases (2/3) EMC was located in the hips, thighs, knees, and wrists, similar to those reported in the literature. Atypical EMC locations included the nasopharynx, lower jaw, chest, abdomen, and spine. The average diameter of EMC was found to be 5.5 cm (1.5~8.9cm). Depending on their locations, EMC tumors were more likely to be diagnosed when patients suffered from nerve compression symptoms. These tumors exhibited smaller diameters. EMC has a 5-year survival rate of 100% and a 10-year survival rate of approximately 70% [
There was no specificity of CT findings for primitive EMC [
Tumor calcification, additionally, had not been reported in the literature. However, different forms of calcification were found within the tumors in 3 cases in this study, one of which was a large tumor located in the right thigh and the pelvic areas. Calcification was mainly shown as a large amount of spots and patches in the tumor peripheries. Under microscope, tumor stromal necrosis was observed, leading to a secondary calcium deposition. No calcium was present in the central area with mucus.
EMC was characterized by the presence of cartilage matrix on MR images [
It is essential to differentiate EMC from extraskeletal mesenchymal chondrosarcoma, which is also rare. As the histologic overlap between EMC and other epithelioid and myxoid soft tissue neoplasms is noteworthy, especially at the high-grade end of the spectrum, it is difficult to exclude the fact that some of the tumors included in these series may represent alternative diagnoses [
One limitation of this study is that it is a retrospective and multicenter study due to the rareness of EMC, and a single inspection method is not sufficiently conducive to the determination of EMC. The second limitation is that only 4 cases had both CT and MRI scans, with one case lacking an enhanced CT scan and another case lacking an enhanced MRI scan. Two cases (cases 2 and 13) did not show definite enhancements on CT scans (CT number increases were less than 10 HU). It is unknown whether enhancement and enhancement patterns on MRI would have been observed due to the lack of MRI scans. Future large-scale studies need to be performed to further improve the characterization of EMC.
Preliminary conclusions can be reached by combining the literature and the findings in this study. EMC is likely to exist at certain ages in certain genders (older men) and in specific body regions (limbs, trunk, and subcutaneous tissues). The existence of EMC is also characterized by tumors with low density (mostly 20-40 HU) and calcifications on CT images, mild or no enhancement on enhanced CT images, lobulated hyperintensity on T2WI, and peripheral or septal enhancements on contrast-enhanced MRI. However, EMC cannot be distinguished from common extraskeletal chondrosarcoma using MRI only. Therefore, diagnosing this disease with both CT and MRI exams is recommended.
All authors declare that they have no conflicts of interest.
Ling Zhang and Ruoning Wang contributed equally to this work.
This work was supported by the China Science and Technology Planning Project of Guangdong Province (2016ZC0058) and China Medical Research Fund of Guangdong Province (A2017496).