Like florid reactive periostitis, BPOP (also known as Nora's lesion) is also a rare in relation to the long bones (and shows overlapping radiologic and histologic thus it is crucial to diagnostically separate this entity from reactive periostitis. osteochondromatous proliferation (Nora's lesion), and periosteal .. Nora's lesion, a distinct radiological entity? Skeletal Radiol. This relationship is usually well delineated in lesions of long bones, particularly .. features with osteochondroma but pathologically represents a distinct entity. The lack of anaplasia and distinct radiographic appearance should lead to the . proliferation (BPOP or Nora lesion) and florid reactive periostitis (,–,).
We decided to perform a subungual approach, lifting the nail plate, which allowed a dorsal view of the terminal toe phalanx. We have also removed the portion of the nail which presented alterations. The dimensions of resected segment excluding the nail were 1,3 x 1,8 x 1,1 cm and the lesion was well circumscribed and presented a narrow base Figure 2.
The histopathology revealed areas of hypercellular cartilage, which presented a bluish color, large chondrocytes and endochondral ossification.
Moreover, bony trabeculae presented a rim of osteoblasts and the intertrabecular spaces were filled with fibroblastic tissue. There were no signs of malignancy. The postoperative radiography did not show any signs of lesion. The patient did not receive any other therapy. At this moment, one year after surgery, the patient has no symptoms or signs of lesion recurrence. Figure 2 Macroscopic appearance of the osteocartilaginous resected segment: It is described as a distinct entity containing atypical and bizarre cartilage that often undergoes a characteristic irregular ossification 5.
It occurs mainly in adults and its occurrence in children and adolescents was only rarely described in the literature. Its gross appearance was similar to that of a small osteochondroma or a subungual exostosis. At first, according to physical examination and radiological findings, we admitted the diagnosis of subungual exostosis. In this regard, some radiological exams can be valuable. Moreover, this will inform about its behavior and prognosis.
Histopathologically the lesion had three components: Subungual exostosis occurs mostly on the terminal phalanx of the great toe. It may be preceded by a history of trauma and usually presents as a painful nodular growth or as an externally visible localized lesion that erodes the overlying tissue. Plain radiography normally shows an outgrowth with trabeculated pattern of cancellous bone with or without defined cortex. Resection of its capsule and decortication of the underlying cortical bone is reported as fundamental to reduce recurrence rates.
However, a longer follow-up is essential as recurrence is reported to occur from 10 to months after surgery.
Nora’s lesion: a rare tumor in the pediatric population
However, it seems not to be related with physical trauma. The imaging appearance of certain lesions observed in the long bones seem to be more aggressive than previously thought, demonstrating infiltration of the soft tissue at the periphery and cortical destruction along with medullary infiltration [ 39 - 12141718 ].
In this study, information regarding cortical changes could be obtained only for 18 of the 43 lesions. In three cases, the margins of the lesions were not clearly defined, and there were lucent areas within the lesion itself. Information regarding medullary invasion and soft tissue retention marrow involvement, soft tissue extension could be obtained only for 17 of the 42 patients.
Medullary invasion and soft tissue retention were identified in four Due to their radiological features, the major challenge was differentiating these lesions on the long bones from radiologically similar conditions, especially from malignant bone tumors, such as parosteal, classic osteosarcoma and chondrosarcoma.
Taking into account the data in the literature, and based on our own opinion, we believe that this lesion observed in the long bones consists, clinically and radiologically, of four phases, and that the radiological imaging of these lesions varies according to location and stage.
Initially, the lesion is located in the soft tissue adjacent to the bone, with no continuity between the lesion and the bone cortex. This stage stage I is similar to the radiological and clinical findings of myositis ossificans [ 81920 ].
The lesion then begins to grow slowly, forming a radiolucent line zone between the lesion and the adjacent cortex. In this stage stage IIthe radiological and clinical findings are similar to those of parosteal osteosarcoma [ 520 ].
In the next stage stage III [ 1112 ], and the lesion comes into contact with the cortex. Cortical thickness or cortical destruction then begins to develop. The clinical and radiological findings are similar to those of florid reactive periostitis and periosteal malignant bone tumors.
In the last stage stage IV [ 1017 ], and the lesion causes cortical perforation, along with medullary invasion. The radiological and clinical findings are similar to those of malignant bone tumors, such as osteosarcoma and conventional chondrosarcoma.
There is no disagreement regarding the histopathological features of the lesion. Histologically, the lesions are characterized by three components: Histologically, BPOP presents as a cartilage-capped exostosis. The cap is cellular with focal atypia, and the subchondral area is composed of fibrovascular tissue.
The presence of an unusual form of calcified cartilage that stains blue on hematoxylin and eosin stain is characteristic. The absence of cellular atypia helps distinguish this lesion from malignant bone tumors, such as osteosarcoma and chondrosarcoma.
Some authors believe that the initiating event is trauma with subsequent subperiosteal hematoma [ 20 ]. In some cases, with available follow-up imaging, Dhondt et al [ 13 ] noticed a radiographic evolution, from the more characteristic FRP to BPOP, and finally, to turret exostosis. In support of this theory, Sundaram et al [ 15 ] reported a series of three patients with presumptive diagnoses of FRP based on radiological findings. These lesions were allowed to progress, and imaging findings were suggestive of BPOP.
However, histological correlation for each imaging stage was not available. Within the context of the review performed in our study, no histopathological study in support of this theory could be found.
On the other hand, this lesion may have findings that are radiologically and clinically similar to other lesions, such as MO, FRP, osteochondroma and turret exostosis. However, we do not agree with the view that this lesion represents an intermediate stage of other lesions, such as MO, FRP, osteochondroma and turret exostosis. This is because we believe that BPOP has the radiological stages mentioned above, and that each stage bears the histopathological characteristics of BPOP.
The diagnosis of each one of these lesions was confirmed with histopathological examination. The first was a lesion in the femur, which also demonstrated cortical invasion stage IIIwhile the second case was localized entirely within the soft tissues, with no demonstrable attachment to the underlying bone stage I. It was postulated that this second case might reflect a very early case of histologically proven BPOP that could have been confused with myositis ossificans.
As it is localized in the long bones, it is difficult to distinguish this lesion clinically and radiologically from many other tumors or tumor-like lesions. Differential diagnosis considerations for this lesion include myositis ossificans, turret exostosis, florid periostitis, osteochondroma and osteosarcoma.
The main differential diagnosis to be considered is myositis ossificans. This non-neoplastic lesion generally occurs adjacent to the larger muscles following trauma, and it has a centripetal pattern of ossification. When a cartilaginous component is present, it is distributed haphazardly. Turret exostosis and florid periostitis are related reactive processes of the bone that can have characteristics radiologically similar to BPOP. The cortical and medullary continuity in osteochondroma is uniform and without interruption.
Radiologically, they can mimic malignant tumors, such as osteosarcoma and chondrosarcoma. It is sometimes difficult to obtain a differential diagnosis for these tumors clinically and radiologically, thus necessitating a histopathological examination for proper identification.
Although it is known that this lesion is more commonly localized in the short, tubular bones within the skeletal system, we nevertheless believe that this lesion is not as uncommon to the long bones as is generally presumed. In this context, we believe that difficulties are experienced in its diagnosis due to its ability to mimic many different types of lesions radiologically. As such, a multidisciplinary approach to diagnosis will likely result in the best outcome for the patient. One of the most significant problems encountered with this disease is treatment.
Reporting of this lesion in the long bones is particularly uncommon, with most reports being performed as case presentations.
Among the rare case presentations that are reported, the lack of a common language regarding the applied treatment techniques, along with the fact that views regarding the disease etiology and the natural course of the disease are limited to assumptions, precludes the development of a common perspective regarding the treatment of this disease.
There are many points that need to be answered regarding the treatment process. First of all, should the lesion be treated? Second, should the lesion be monitored? Third, if surgery is to be performed, which surgical technique should be applied?
In this study, surgical treatment was conducted in all cases except one. However, despite the fact that nearly all papers are presented in a case report format, no detailed information was provided regarding the applied surgical techniques, nor was a common language used regarding the applied surgical techniques. Despite all these shortcomings, it is now known that this disease involves lesions that may be potentially progressive.
Based on the currently available information, it is difficult to assess beforehand which types of lesions are capable of progression. Furthermore, although progression has been reported in BPOP, no cases of regression or spontaneous healing have been reported.
As such, surgical resection should be the preferred treatment method, without resorting to disease monitoring. Therefore, caution must be exercised when selecting the surgical technique to be performed.
Intralesional excision and curettage appear to involve a high risk of local recurrence on the lesions observed in the small bones; therefore, these techniques should not be performed for the surgical treatment of the lesion. On the other hand, due to the high recurrence rate and occasionally atypical histological appearance of the lesion, we also believe that it is necessary to avoid wide resection techniques that might require serious reconstructive surgeries and which have high mortality rates, as no malignant transformations, metastases, deaths, or associated systemic diseases have been described thus far for patients with BPOP.
Our lack of sufficient knowledge and experience regarding this lesion, along with the fact that a common language has not been used when describing the treatment of reported cases, precludes us from presenting optimal information regarding the treatment of this disease.
However, our opinion is that marginal resection might be sufficient for the treatment of this disease. By this, we mean a marginal excision that includes the resection of the reactive zone.
This technique involves the removal of the pseudocapsule and periosteum, the decortication of underlying abnormal host bone, and the administration of intralesional curettage and local adjuvant therapy to the medullary component. Depending on its stages, we believe that the surgical technique to be administered in stages I and II of the lesion is marginal resection, while the administration of local adjuvant therapy phenol and cauterization in addition to marginal resection should be sufficient for stages III and IV.
Lesions observed in the small bones have a remarkable tendency to recur. No recurrence rates have been reported to date for lesions localized in the long bones. In this study, local recurrence was observed in three of 16 lesions.