Japanese Journal of Clinical Oncology 31:168-171 (2001)
© 2001 Foundation for Promotion of Cancer Research
Atypical Bone Metastasis and Radiation Changes in a Colon Cancer: a Case Report and a Review of the Literature
1Department of Therapeutic Radiology and 2Department of Radiology, Chosun University Hospital, Chosun University College of Medicine, Kwangju, Republic of Korea
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ABSTRACT |
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We report a unique case of skeletal metastasis with prominent soft tissue extension from a colon cancer in a 44-year-old male patient. Four years after the diagnosis of colon cancer, plain radiographic examinations revealed a prominent soft tissue mass associated with cortical destruction of the right femur. Palliative radiotherapy of the right femur was performed. After completing radiotherapy, massive remineralization was seen in the soft tissue component. With the assistance of pre- and post-radiotherapy computerized tomography images, obtained in the process of planning the radiotherapy, we reached the conclusion that in our case the pre-radiotherapy finding was an extreme case of eccentric expansion of the bony cortex due to the outgrowth of bony metastasis. Retrospectively, the initial prominent soft tissue mass associated with the cortical destruction seems to have been a protruding bone metastasis, extending from the medial aspect of the right femur. This peculiar feature with remineralization after radiotherapy should help explain the phenomenon of atypical bony metastasis from a radiological perspective.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONREFERENCES |
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When patients present with metastatic bone disease, the search for a primary may be helped by considering the appearance of lesions. Informative patterns include lytic and sclerotic lesions, ‘expanded’ lesions, ‘pseudo-sarcomatous’ lesions, acral lesions and soft tissue ossification (1).
The detection of prominent soft tissue masses associated with cortical destruction (pseudo-sarcomatous lesions) favors a diagnosis of a primary malignant lesion of bone, rather than a secondary deposit associated with bony metastasis. Nevertheless, colon cancer may metastasize to bone, producing soft tissue masses that occasionally contain calcification (2).
We report a case of atypical bone metastasis with prominent soft tissue extension from colon cancer. We focus on the radiographic findings pre- and post-radiotherapy and on post-radiation changes, which showed osteoblastic activity and peculiar remineralization in the soft tissue extension. We also present a review of the literature.
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CASE REPORT |
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A 44-year-old Korean male was admitted to the emergency room in September 1999 with painful swelling of the right thigh, inability to walk and severe constipation.
He had had a right hemicolectomy for colon cancer, located in the ascending colon near the hepatic flexure, in August 1995. The surgical specimen was a 5.7 x 3.2 cm ulcero-infiltrative tumor. The pathological findings were consistent with well-differentiated adenocarcinoma, with extension to pericolic fat and endolymphatic tumor emboli. Five out of 107 regional lymph nodes were infiltrated by adenocarcinoma. There was no perineural invasion and the resection margins were negative in all directions. The patient received 12 cycles of chemotherapy, with a regimen containing 5-FU and levamisol.
In May 1999, he visited the outpatient department (OPD), complaining of pain in the right thigh. Bone scintigraphy showed increased uptake in the right femur. Metastatic recurrence was diagnosed and palliative radiotherapy was advised; however, the patient refused treatment. He did not visit the OPD again and was lost to follow-up at that time.
On his admission to the emergency room 4 months later, plain radiographs of the right thigh were taken. The oblique view of the right hip demonstrated osteolytic bone destruction in the trochanteric area of the right femur, with cortical destruction accompanying a pathological fracture. A large soft tissue mass, with faint calcification, extended from the medial aspect of the bone destruction (Fig. 1a). His general condition was poor and radiotherapy was the only possible treatment. The fractured femur was splinted in the emergency room, then simulation for radiotherapy was performed. After the simulation procedure, a computerized tomography scan was taken for radiotherapy planning. This revealed considerable bone destruction, with a soft tissue mass and faint calcification, in the medial aspect of the right proximal femur (Fig. 2a). Concentric thickening of the rectal wall was noted and considered to be the cause of the patient’s severe constipation.
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Palliative radiotherapy of the right femur was performed, with a total dose of 30 Gy, given in daily 3 Gy fractions. After completion of radiotherapy to the right femur, follow-up radiographic examinations were undertaken. One month after radiotherapy, the oblique view of the right hip showed osteoblastic bone formation of the previously noted osteolytic lesion and a protruding expansile bony mass in the medial aspect of the right femoral neck (Fig. 1b). 99mTc–methylene diphosphonate (MDP) bone scintigraphy showed abnormally increased uptake in the right proximal femur (Fig. 3). Thereafter, palliative radiotherapy was given for the rectal mass lesion. The total dose of pelvic irradiation was 40 Gy with daily 2 Gy fractions. Non-contrast CT images taken in the process of radiotherapy planning showed a ballooning osteolytic–osteoblastic mass of protruding bone in the medial aspect of the right femoral neck (Fig. 2b). In addition, continuity of the cortical periosteum of the bulky encircled bone mass was suggested (Fig. 2b). Two months after radiotherapy to the right femur, the oblique view of the right hip showed more osteoblastic changes in the lesion (Fig. 1c).
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The patient expired at his home in April 2000. We could not determine the exact cause of death, because we were notified of his death by a telephone call from his wife and no autopsy was performed. Stool passage was maintained until his death, so the palliative pelvic radiotherapy was considered successful.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONREFERENCES |
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Skeletal metastasis of primary colorectal cancer is uncommon and is usually a late manifestation of the disease. Cayla et al. reported 11 cases and discussed the characteristics of bony metastases in carcinoma of the colon and rectum (3). The frequency of these metastases is fairly low (1.3% of all cases of bony metastases). Radiographically, metastases usually give rise to osteolysis. However, a mixed osteolytic–osteoblastic appearance is not rare and usually has a pseudo-sarcomatous appearance, with invasion of soft tissue and very marked periosteal reactions. Seife (2) had the same impression: skeletal metastases from carcinoma of the colon or rectum are generally osteolytic or mixed osteolytic–osteoblastic and an adjacent soft tissue mass containing calcification is occasionally evident. This radiological finding usually favors diagnosis of a primary malignant lesion of bone, rather than a secondary deposit associated with bony metastasis. Nevertheless, exceptions are encountered in certain locations and with certain types of neoplasms. Documentation by Cayla et al. and Seife suggests that differential diagnosis should include bony metastasis from colon cancer when pseudo-sarcomatous lesions with invasion of soft tissues and very marked periosteal reactions are encountered in patients with a diagnosis of colon cancer.
There are few reports of abnormal calcification in metastatic cancer from a primary colonic malignancy. Some researchers (3,4) have reported calcifying activity by non-osseous metastatic tumors arising from colon cancer. In addition, there are reports suggesting roles for cytokines and osteoblast stimulating factor produced by tumor cells in the process of osteoblastic metastases (5). In our case, however, the faint calcification within the soft tissue shadow was considered to be from the combined action of marked osteolysis and a shift of cortical bony fragments due to expansile growth of the metastatic tumor. This could offer a clue, because alignment of the calcific densities with non-contrast axial CT images showed an organized pattern that converged on the epicenter of the soft tissue mass and cortical destruction (Fig. 2b).
CT changes after radiotherapy are rarely reported. Wachenfeld et al. (6) evaluated the CT scans of 14 patients with multiple metastases of mammary carcinoma. They saw increased bone mineral density in osteolytic metastases 6 weeks after therapy, which was more distinct 3 months later. Weber et al. (7) investigated the radiotherapeutic effect on the rate of recalcification. After a total dose of 30 Gy, remineralization was observed in 70% of cases. In our case, non-contrast CT images taken in the process of radiotherapy planning for the rectal mass showed a massive atypical remineralization change in the soft tissue component of the metastasis (Fig. 2b) and 99mTc–MDP bone scintigraphy 1 month after treatment showed an abnormally increased uptake in the soft tissue mass, evidence of active ongoing reossification (Fig. 3).
In a review of the literature, from the era of plain radiography, there was some confusion between prominent soft tissue masses associated with cortical destruction (pseudo-sarcomatous lesions) and soft tissue within an expanded cortex (expanded lesions) with regard to atypical metastatic features. In our opinion, one point helps to distinguish the two: most expanded lesions are purely osteolytic, whereas pseudo-sarcomatous lesions contain calcific foci in the soft tissue components.
In our case, pre- and post-radiotherapy CT images gave the impression that the initial finding of prominent soft tissue extension was an extreme example of eccentric expansion of the bony cortex, with the formation of a ballooning soft tissue mass within the expanded cortex by metastasis. Additional features distinguishing pseudo-sarcomatous and expanded lesions may be whether the periosteum tears and whether the malignant cells have calcifying activity.
Although in any discussion of the features of atypical metastasis from colon cancer our case has limitations, because of the lack of histological confirmation, some points did indicate metastasis and suggest this conclusion. First, although plain radiographic findings favored a diagnosis of primary bone malignancy, our case had a history of antecedent colon cancer. Primary bone tumors are rare. Whenever a skeletal neoplasm is encountered, metastases should be prominent in the differential diagnosis, especially in adults. Only after metastases have been excluded should a primary bone malignancy be considered (8). Second, with the assistance of pre- and post-radiotherapy CT images, the initial plain radiographic findings in our case were considered to show an unusual expansile metastatic lesion, rather than a pseudo-sarcomatous lesion. Therefore, the two peculiar metastatic features observed at the time of plain radiography may not have been different entities, although our limited evidence makes such a generalization speculative. Our observations may help lead to a better understanding of the mechanism of atypical metastases from colorectal neoplasms.
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FOOTNOTES |
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+ For reprints and all correspondence: Yoon Kyeong Oh, Department of Therapeutic Radiology, Chosun University Hospital, Chosun University College of Medicine, 588 Seosuk-dong, Dong-ku, Kwangju 501-140, Republic of Korea. E-mail: ykoh@mail.chosun.ac.kr
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REFERENCES |
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1 Rosenthal DI. Radiologic diagnosis of bone metastasis. Cancer 1997;80:1595–607.[Web of Science][Medline]
2 Seife B. Osseous metastases from carcinoma of the large bowel. Am J Roentgenol 1973;119:414–8.[Web of Science]
3 Cayla J, Rondier J, Forest M, Heisbourg A, Meary R. Bone metastases of colonic and rectal neoplasms. Apropos of 11 cases. Sem Hop 1975;51:507–18.[Medline]
4 Wong LL, Peh WC. Clinics in diagnostic imaging (22). Calcified peritoneal carcinomatosis. Singapore Med J 1997;38:88–91.[Medline]
5 Mundy GR. Mechanisms of osteolytic bone destruction. Bone 1991;12(Suppl 1):S1–S6.
6 Wachenfeld I, Sanner G, Bottcher HD, Kollath J. The remineralization of the vertebral metastases of breast carcinoma after radiotherapy. Strahlenther Onkol 1996;172:332–41.[Medline]
7 Weber W, Rosler HP, Doll G, Dostert M, Kutzner J, Schild H. The percutaneous irradiation of osteolytic bone metastases – a course assessment. Strahlenther Onkol 1992;168:275–90.[Medline]
8 Moser RP, Madewell JE. An approach to primary bone tumors. Radiol Clin North Am 1987;25:1049–93.
Received October 16, 2000; accepted January 4, 2001.
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