M.D. 2, and Robert J. Maurer, M.D. 3. Departments of 1 Radiology, 2 Pathology and 3 Orthopedic Surgery, Penn State University Hospital, The Milton S. Hershey ...
Skeletal Radio1 (1991) 20:628 632
Skeletal Radiology
Case report 704 Thomas M. Doud, M.D. 1, Richard P. Moser, Jr., M.D. 1, Michaela A.I. Giudici, M.D. 1, Elizabeth E. Frauenhoffer, M.D. 2, and Robert J. Maurer, M.D. 3 Departments of 1 Radiology, 2 Pathology and 3 Orthopedic Surgery, Penn State University Hospital, The Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033, USA
I m a g i n g studies
Fig. 1. Continued next page 9 1991 International Skeletal Society
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Fig. 1. A Frontal radiograph shows a large, densely clacified mass (diameter = 13 cm) in the medial soft tissues of the right thigh. B Posteroanterior (PA) and C lateral chest radiographs demonstrate diffuse, bilateral, pulmonary metastases of varying size. These metastases are disproportionately distributed adjacent to the heart. D Methylene diphosphonate (MDP) scintigram demonstrates marked radionuclide accumulation in the soft-tissue lesion in the thigh and diffuse uptake in the chest. Based exclusively on the scintigram, it is impossible to localize precisely the sites of the lesions of the chest (e.g., pulmonary parenchymal, pericardial, or osseous). Also noted were three foci of increased radionuclide uptake in the proximal end of the right femur and right hemipelvis. Only two of these foci (arrows) are apparent on this image. The third focus was
near the right sacroiliac joint and was readily apparent on the posterior image. E--G Axial CT scans with soft-tissue (E) and bone (F, G) windows demonstrate a large, sharply demarcated, densely but inhomogeneously calcified mass in the medial soft tissues of the right thigh. On all CT cuts, although the medial border of the mass is in close anatomic proximity to the adjacent femoral cortex, there is a distinct separation (arrows in E, F) between the mineralised soft-tissue mass and the femur. Overall, there was more extensive mineralization in the center of the soft-tissue mass (G). On one cut there was an area of increased attenuation (arrow in G) in the proximal end of the diaphysis of the right femur, corresponding to a focus of increased radionuclide activity on the scintigram. H CT scan through the midchest demonstrates multiple bilateral pul-
monary lesions. The cardiac contour is markedly irregular due to pericardial and/or pulmonary parenchymal disease adjacent to the heart. In addition, coexistent pericardial effusion cannot be excluded. I, J Axial magnetic resonance (MR) scans (2500/30) demonstrate a large, sharply demarcated, inhomogeneous, soft-tissue mass. On several scans an interesting nodular pattern (arrows) within the lesion is noted. K Coronal MR scan (600/30) also demonstrates inhomogeneous signal throughout the sharply demarcated soft-tissue mass (large arrows) in the medial tissues of the thigh. Adjacent to the mass is an area of abnormal signal (small arrows) in the proximal end of the diaphysis of the right femur. This corresponded to an area of increased activity on bone scan (D) and increased attenuation on CT (G)
Clinical information
unremarkable. Physical examination c o n f i r m e d the presence o f a firm, tender mass (measuring approxim a t e l y 16 x 14 cm) in the m e d i a l soft tissues o f the right thigh. N o signs o f n e u r o v a s c u l a r c o m p r o m i s e were present. L a b o r a t o r y findings were w i t h i n n o r m a l limits, except for a n e l e v a t e d a l k a l i n e p h o s p h a t a s e o f 189 ( u p p e r limit o f n o r m a l is 130). R a d i o g r a p h s o f the t h i g h r e v e a l e d a large, densely m i n e r a l i z e d , m e d i a l , soft-tissue mass. B o n e scan s h o w e d i n c r e a s e d u p t a k e (a) in the soft-tissue
m a s s in the thigh, (b) diffusely in the chest, (c) in the p r o x i m a l end o f the d i a p h y s i s o f the right f e m u r ( a d j a c e n t to the soft-tissue mass) a n d (d) in t w o l o c a t i o n s in the r i g h t hemipelvis. A chest r a d i o g r a p h d e m o n s t r a t e d diffuse, bilateral, p u l m o n a r y lesions. C T a n d M R scans clearly d e l i n e a t e d the e x t e n t o f the soft-tissue m a s s in the thigh. N o evidence o f c o r t i c a l inv o l v e m e n t o f the a d j a c e n t f e m u r was noted. A b i o p s y was p e r f o r m e d .
This 6 7 - y e a r - o l d w o m a n c o m p l a i n e d o f p a i n in the right t h i g h o f 2 weeks' duration following detection of a p a l p a b l e m a s s in the m e d i a l soft tissues o f the thigh. A l t h o u g h h e r prim a r y care p h y s i c i a n i n i t i a t e d a s h o r t course of nonsteroidal antiinflammat o r y agents, the s y m p t o m s persisted. A p p r o x i m a t e l y 3 weeks later, a n o r t h o p e d i c c o n s u l t a t i o n was o b tained. P a s t m e d i c a l / s u r g i c a l h i s t o r y was
630 Diagnosis: Extraskeletal osteosarcoma of the thigh with several suspected skeletal metastases and extensive metastases to the chest
T.M. Doud et al. : Case report 704 Pathological studies
Grossly, the tissue sampled consisted of multiple, irregular fragments of bony and soft tissue measuring in aggregate 3 x 2 x 0.5 cm. Microscopically, the biopsy demonstrated a high-grade osteoblastic osteosarcoma with focal chondroid differentiation. Prominent osteoid formation by numerous, pleomorphic, sometimes bizarre neoplastic, stromal cells was present. Rare foci of cartilage blended imperceptibly with large irregular islands of bone; the majority of the extracellular matrix produced was osteoid, however. Since there were extensive metastases at initial presentation, no surgical therapy was performed. The patient is currently undergoing the sixth course of her chemotherapy regimen. Discussion
Extraskeletal osteosarcoma is a malignant mesenchymal neoplasm that produces neoplastic osteoid, bone, and occasionally chondroid material [5, 8, 10, 16]. It is located within the soft tissues without attachment to the underlying bone and, therefore, is appropriately considered extraskeletal [8, 16]. Contrasted with osteosarcoma of bone, extraskeletal osteosarcoma is rare, as reflected in a relative ratio of approximately 25:1 [8, 11, 14, 16]. Patients with osteosarcoma of bone typically present between the ages of 10 and 25 years, while those afflicted with extraskeletal osteosarcoma are older [3, 5, 10, 13, 14, 16]. Among others, Enzinger et al. maintain that the mean age at presentation is 54 years
[5, 8]. Scattered reports exist of extraskeletal osteosarcomas arising in diverse locations such as breast, lung, thyroid gland, kidney, prostate and urinary bladder [6, 8, 10, 11, 15]. Most investigators consider the most frequent site of involvement as the lower extremity, especially the thigh [3, 5, 7, 10, 11, 13, 14, 16]. The typical clinical presentation is a slowly growing, soft-tissue mass which may
Fig. 2. Continued next page be (but is not invariably) painful [3, 5, 8, 10, 13, 14]. Most lesions are deeply seated and fixed to the soft tissues [5, 8]. The most common sites
of metastases are lung and liver. Laboratory findings are usually within normal limits except for alkaline phosphatase activity which can be el-
T.M. Doud et al. : Case report 704
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Fig. 2. A Osteosarcoma with large irregular islands of osteoid produced by malignant stromal cells (original magnification x 25). B Irregular islands of osteoid formed by malignant cells (original magnification • 64). C Focal chondroid differentiation in osteoblastic osteosarcoma (original magnification • 25)
evated, especially with metastases [8, 13, 16]. It is unclear what role, if any, antecedent trauma plays in the development of extraskeletal osteosarcoma, which has also been reported as a complication of prior radiation therapy [1, 2, 4, 5, 8, 10-16]. Nevertheless, in the case reported here, the patient denied either prior trauma or radiation exposure. The prognosis of this tumor is poor, and the majority of patients succumb to metastases within 2-3 years from the time of initial diagnosis [5, 10, 11, 13, 16]. Early combination therapy consisting of radical or limb-sparing resection (if possible), radiation therapy, and adjuvant chemotherapy constitutes the current regimen which is most likely to achieve prolonged survival [5, 8, 10, 11, 13, 14, 16]. Most scientific papers concerning extraskeletal osteosarcoma have appeared in the oncological or pathological literature or in journals in which its radiological appearance
was not emphasized [5, 8, 9, 13, 15]. This case is particularly educational because, to the best of our knowledge, it demonstrates several features of extraskeletal osteosarcoma which have not been previously illustrated, e.g., extensive chest metastases, scintigraphic and M R appearance, and suspected skeletal metastases. Furthermore, for correlation, a complete imaging spectrum is available. Radiographs of the patient reported in this case demonstrated a large, densely mineralized, soft-tissue mass in the right thigh, without apparent involvement of the adjacent femoral cortex (Fig. 1 A). The chest radiographs (Fig. I B, C) showed multiple, bilateral, pulmonary metastases, confirmed on CT examination (Fig. 1H). On scintigraphic study (Fig. 1 D), increased radionuclide activity was noted in both the large soft-tissue mass in the thigh and in numerous metastases in the chest. Of additional interest, the bone scan revealed three suspected skeletal metastases, two in the right hemipelvis
and one in the proximal end of the right femoral diaphysis, adjacent to the soft-tissue mass. Computed tomography of the right thigh (Fig. 1 E-G) also identified the sharply demarcated, heavily mineralized soft-tissue mass, with several areas of suspected necrosis within the lesion. The medial border of the soft-tissue mass was in close anatomical proximity to, yet still distinct from, the adjacent femoral cortex. Cortical involvement was not demonstrated. M R I (Fig. 1 I-K) demonstrated a large, sharply demarcated, soft-tissue mass of mixed low signal intensity on Tl-weighted images and mixed, but predominantly high, signal intensity on proton and T2-weighted images. Within the marrow of the adjacent femoral shaft, decreased signal was detected on Tl-weighted images. This finding corresponded to subtle increased attenuation on CT (Fig. 1 G) in an analogous location. The imaging studies of this patient demonstrated some particularly interesting features. (1) On the chest radiograph, the pulmonary parenchymal metastases were disproportionately "clustered" around the h e a r t findings confirmed by CT and scintigraphy. In fact, the CT and scintigraphic images suggested possible pericardial metastases. When the scintigraphic images were interpreted initially, metastases of ribs could not be excluded, although when correlated with the chest radiograph, this possibility was deemed unlikely. (2) Both CT and M R images (Fig. 1 EG, I K) suggested that the extraskeletal osteosarcoma was well-marginated. These tumors are typically delineated by a "pseudo-capsule", however, beyond which additional malignant material is frequently encountered on careful histological examination [5]. The M R scan (Fig. 1 J) also revealed an interesting appearance of lobulation within the tumor, but the significance of this finding is unclear [5]. (3) To the best of our knowledge, skeletal metastases from extraskeletal osteosarcoma have been mentioned on only a few occasions in the literature, and we were unable to identify any radiological illustrations of this phenomenon [3, 16]. Due to the large size of
632 the soft-tissue mass in this case, we believe the m a l i g n a n c y clearly arose in the thigh. O n the radiographs, there was no discernible lesion in the proximal diaphysis o f the right femur. In this latter location, however, abnormalities were n o t e d on the scintigram, CT and M R image (Fig. 1 D, G, K) - highly suspicious for a skeletal metastasis, particularly considering the extensive metastases in the chest. The scintigram also suggested two metastases in the pelvis, alt h o u g h this area was n o t assessed by C T or M R I . The radiographic differential diagnosis o f extraskeletal osteosarcom a includes synovial sarcoma, chond r o s a r c o m a o f soft tissue, liposarcom a o f soft tissue, a n d myositis ossificans [10]. D u e to the extensive mineralization within the lesion (Fig. I A), only myositis ossificans was a reasonable alternative diagnosis to extraskeletal o s t e o s a r c o m a [10, 14]. Naturally, the presence o f the extensive metastatic disease excluded the diagnosis o f myositis ossificans. In addition, on C T scan (Fig. 1 F) the mineralization within the mass was greatest in the center o f the lesion and least at the periphery. This pattern is typical for mineral encountered in a soft-tissue s a r c o m a but is the opposite o f that associated with
T.M. Doud et al. : Case report 704 myositis ossificans, where the degree o f opacification is greatest at the periphery o f the lesion [5, 8, 10, 11, 14]. In summary, a case o f extraskeletal o s t e o s a r c o m a occurring in its m o s t c o m m o n location, the thigh, is reported. Particular emphasis is given to d e m o n s t r a t i n g the spectrum o f radiological findings, including CT, M R I , and scintigraphy and to illustrate that this entity can metastasize to bone.
Acknowledgment. We would like to thank Ms. Constance Gardner-Hornyak for her expert support in preparation of the manuscript.
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