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Indian Journal of Cancer, Vol. 48, No. 3, July-September, 2011, pp. 368-370 Letter to Editor Concurrent occurrence of transarticular and intramedullary skip metastases in osteosarcoma of distal femur detected on plain radiographs YS Siddiqui, M Zahid, AB Sabir, G Kumar Department of Orthopaedic Surgery, J.N. Medical College, Aligarh Muslim University, Aligarh, India Code Number: cn11096 PMID: 21921342 DOI: 10.4103/0019-509X.84916 Sir, Osteosarcoma in association with skip metastasis is of rare occurrence. [1] When multiple bone lesions are simultaneously present at diagnosis, it is a synchronous multifocal osteosarcoma, whereas when the bone lesions appear at different intervals, it is a metachronous multifocal osteosarcoma. Whether these tumors are multicentric in origin or are bone metastases is controversial. [2] We are describing a case of osteosarcoma of distal femur in a 14-year-old girl, in whom the synchronous skip lesion was detected not only intramedullary in proximal femur, but also across the knee joint involving proximal tibial epiphysis, with no evidence of lung metastases. Examination revealed tender swelling [Figure - 1] with painful restriction of knee movements. Radiographs revealed typical appearances of osteosarcoma with skip lesions in proximal femur and proximal tibial epiphysis [Figure - 2], [Figure - 3] and [Figure - 4]. Computed tomography (CT) scan of the chest was normal. Blood investigations revealed low hemoglobin levels, raised serum alkaline phosphatase and lactate dehydrogenase levels. Fine Needle Aspiration Cytology from the distal femur and proximal tibial lesion was consistent with diagnosis of high-grade osteosarcoma. Bone scan was not done as the patient belonged to low socioeconomic class. However, clinical investigations and plain radiographic skeletal survey did not reveal any abnormality. According to the American Joint Committee on Cancer (AJCC) classification system, our patient was classified as having stage IV disease (as the patient was having transarticular skip lesion). Skip metastases are foci of tumor cells within the same bone as the primary lesion but are separated from the primary focus by normal intervening marrow. Occasionally, they may arise at the opposing side of a joint, [3] as in our patient. Skip lesions are a well-recognized feature of osteosarcoma and are associated with a poorer prognosis than cases clear of such lesions. [4] The inability of the plain radiographs to recognize the skip lesions is due to insufficient trabecular destruction by the lesion confined to the medullary cavity. It is well recognized that in the absence of cortical bone loss, approximately 50% of the underlying trabecular bone needs to be destroyed for it to be discernible radiographically. [5] In our patient, both skip lesions were detected on plain radiographs, though this is not true in all cases of multifocal osteosarcomas. However, skip metastases are best analyzed with long axis imaging of the entire affected bone. In localized osteosarcoma, the association of chemotherapy-surgery has indisputably improved prognosis. The role of chemotherapy combined with aggressive surgery has not been investigated in patients with synchronous multifocal osteosarcoma which is considered a fatal disease within a year. Hence, identifying skip metastases is important, both for defining local extent of the tumor and for prognostic reasons, as patients with skip metastases are more likely to also have distant metastases, which correspond to a lower 5-year survival rate than for those who do not have distant metastases. [4] In the present case, magnetic resonance (MR) imaging was not done, as both skip lesions were clearly visible on plain radiographs. Moreover, MR imaging would not change the management plan of our patient. Detection of skip lesions changed the management plan of our patient from endoprosthetic replacement of her distal femur to hip disarticulation which can be expected to give her better survival. Patient and her parents refused hip disarticulation, and she was managed with multi-agent chemotherapy alone. After three cycles of multi-agent chemotherapy, the size of the tumor marginally reduced clinically, with no variation in the size of skip lesions observed on plain radiographs. At her latest follow-up, 8 months after the initial presentation, the patient had developed multiple pulmonary metastases. Synchronous skip metastases are not always demonstrable on plain radiographs. An error in detecting skip metastases would result in continued local destruction and distant spread of the tumor. Hence, we advise MR imaging study of the bone involved along with proximal and distal joints in all cases of osteosarcomas. References
Copyright 2011 - Indian Journal of Cancer The following images related to this document are available:Photo images[cn11096f3.jpg] [cn11096f2.jpg] [cn11096f4.jpg] [cn11096f1.jpg] |
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