2.4 Follow-up and outcomes
The patient was discharged without any complications 10 days after surgery. In addition, this patient's follow-up after 4 years showed no signs of recurrence or metastasis (Fig. 4).
PO is a rare type of bone tumor. Dwinell et al reviewed 400 cases of osteosarcoma in 2000 cases of primary bone tumors and found 15 cases of PO, accounting for 0.75% of all primary bone tumors and 3.8% of osteosarcoma. PO onset generally occurs between the ages of 20 to 40, usually in the lower femur, upper tibia, and popliteal fovea. Therefore, most of the studies on diagnosis and treatment of PO focus on young people and the effect on the femur. However, diagnoses of PO at other ages and uncommon sites are rarely mentioned.
Diagnosis of PO emphasizes the triple combination of clinical, radiographic, and pathologic findings. The typical PO has a slow onset, mainly presenting as a painless and gradually increasing mass, with approximately 86% of cases being palpable, and about 33% of cases having adjacent joint activity limitation. In the present case, the tumor was consistent with others reported in the literature as it was a painless, palpable mass but the patient had no adjacent joint activity limitation. Generally, imaging examinations of PO show the shape and size of the bone tumor by X-ray plain film, while the CT and MRI show the relationship between the tumor and bone and the degree of invasion of the medullary cavity.[13,14] There was a comprehensive assessment of the relationship and degree of invasion between the area of the tumor soft tissue mass and the vascular nerve, which was of significant use for the clinical diagnosis and formulation of the surgical program. The major pathologic feature of PO is that the gross tumor is a hard bone mass attached to 1 side of the epiphyseal cortex or half a week. Microscopically, the neoplastic trabeculae and active fibrous interstitium contained no obvious heterogeneity, pleomorphism, or nuclear division of tumor cells. Hence, when clinical and imaging identification is difficult, pathological biopsy should be performed to obtain an accurate preoperative diagnosis to improve treatment planning.
Early diagnosis of PO of the peroneal bone in middle-aged or elderly patients is difficult and misdiagnosis or missed diagnosis is common. PO should be differentiated from benign tumors that mainly include ossifying myositis and florid reactive periostitis. Special attention should be paid to the identification of osteochondroma. In this case, according to the clinical history and imaging features of the patient, the experienced radiologist found that PO was misdiagnosed as osteochondroma, which may be due to the following factors: first, incidence of PO in middle-aged or elderly individuals is extremely rare; second, both osteochondroma and PO present as painless, slow-growing, textured hard masses; third, after the discovery of lesions and due to similar imaging performance, clinicians tend to focus on more common diseases. Moreover, myositis ossificans usually has a history of trauma and pain, and its ossification is around the lesion, while the ossification of PO is at the center of the tumor. Whether the tumor encroaches on normal bone is also an important basis for differentiation. Florid reactive periostitis is a common disease of the phalanx and nearly 40% of the patients have a history of trauma. Histology predominantly indicates the proliferative fibroblast lesions, which often involve osteoid tissue. However, unlike in PO, the tumor edge is the braided bone containing bone marrow and the center is the immature area with abundant cells.
On the other hand, malignant tumors primarily include periosteal osteosarcoma, high-grade surface osteosarcoma, and extracortical infiltration of intramedullary well-differentiated osteosarcoma. Periosteal osteosarcoma is generally associated with relatively small lesions and often presents with a characteristic acicular periosteum.[14,16] In addition, PO should be differentiated from extracortical infiltration of the intramedullary well-differentiated osteosarcoma, which has a similar histology, although most intramedullary well-differentiated osteosarcomas are widely involved with the medullary tissue, while PO usually has focal invasion. Intramedullary well-differentiated osteosarcoma is similar to highly malignant classic osteosarcoma in both X-ray and histological morphology. Unlike PO, high-grade surface osteosarcomas are mainly osteoblast-like and contain little or no cartilage components.
PO has limited remote diffusion potential with local invasiveness. Nevertheless, the presence of bone marrow infiltration and moderate cell atypia did not correlate with a worse prognosis and it has been reported in the literature that PO has a generally good prognosis.[11,20] Therefore, surgical treatment should be actively sought. Simple tumor resection is feasible for patients with smaller tumors and extensive and thorough resection should be performed for patients with larger tumors, invasion of adjacent bone, or recurrence. If the tumor infiltrates important blood vessels or nerves and cannot be completely removed, amputation is considered. In this case, due to moderate tumor size and the absence of vascular or nerve damage, we performed a complete resection of the tumor and a 1-week post-operative radiography showed a complete resection of the tumor. If not completely excised, recurrence may be seen, since the remaining tumor tissue can dedifferentiate and metastasize after recurrence. Hence, great care should be paid during the first operation to achieve complete excision. It has been reported that the 5-year recurrence rates following marginal and extensive resection were 10% and 8.8%, respectively. PO grows slowly, and recurrence and metastasis often occur years after surgery. Patients with incomplete surgery can have multiple recurrences, so multiple surgeries are not uncommon.[22–24] The longest recorded recurrence was 21 years after the initial operation. Therefore, for low-grade malignant tumors of PO, the follow-up time should be long to facilitate close observation. If PO dedifferentiation occurs, it is the same as classic osteosarcoma and is treated in the same manner, with comprehensive treatment dominated by neoadjuvant chemotherapy and surgery. For the typical surgical plan of PO, we advocate that the same method should not be pursued, but full use should be made of highly developed imaging examinations to accurately judge the location, size, and boundary of the tumor, and design different individualized surgical plans. Tumor resection should have a negative resection margin to avoid recurrence and normal tissue and function should be retained as much as possible.
In short, PO of the fibula in middle-aged or elderly patients should not be ignored. Given its rarity, PO should be carefully evaluated. Any analysis based on a single factor or incomplete information may lead to arbitrary diagnosis. We believe that as long as we raise awareness, it is possible to make a correct diagnosis early. In addition, most cases of PO have a good prognosis and should be treated actively. In order to understand this condition better, we recommend that plastic surgeons and radiologists learn to recognize the possibility of PO in older age groups and uncommon locations.
We greatly appreciate the patient and her family for allowing us to make use of the medical documentation and information that led to the present article. We would also like to thank the Editage company in Shanghai, which provided English language editing, for their assistance
DM, and ZB performed the surgery and managed the patient postoperatively. CGP drafted the manuscript. XQ critically revised the manuscript. CGP analyzed the patient data. All authors read and approved the final manuscript.
Funding acquisition: Bin Zhang, Min Dai.
Resources: Bin Zhang, Min Dai.
Supervision: Bin Zhang, Min Dai.
Writing – original draft: Guiping Chen.
Writing – review & editing: Qiang Xu.
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Keywords:Copyright © 2019 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
chemotherapy; imaging; misdiagnosis; osteosarcoma; parosteal osteosarcoma; pathology; surgery