Osteofibrous dysplasia (OFD), also known as Kempson-Campanacci lesion, is a rare benign fibro-osseous lesion predominantly affecting the tibia [1]. OFD-like Adamantinoma (OFD-AD) differs from OFD by the inclusion of small clusters of epithelial cells spread throughout the lesion as opposed to single cells, whereas the classic Adamantinoma (AD) is a malignant biphasic tumor with nests or sheets of epithelial cells that are surrounded by spindle cells with an osteofibrous component. Furthermore OFD-AD shows keratin-expressing epithelial cells which are present as small scattered groups and are visible with hematoxylin and eosin staining; however they may be so sparse that they are overlooked unless they are rendered visible with immunohistochemical staining for keratin. Classic AD and OFD-AD share similarities in location and appearance, representing a continuum making their distinction even more complex [2]. There is some controversy distinguishing OFD-AD or “differentiated adamantinoma” from the classic form with regard to the amount of epithelial component that is compatible with the differentiated form and whether progression from differentiated to classic adamantinoma can occur [3].

Accordingly, there is no consensus regarding the best treatment for OFD. Campanacci and Laus [1] recommended delaying surgery as long as possible because of frequent spontaneous regression during childhood and intervention may even activate progression. Spontaneous regression was surprisingly even seen in a 38-year-old man with a rare variant of OFD with rhabdoid elements [4].

Based on the analysis of 16 patients, Lee et al. [5] recommended radical extraperiosteal excision in all cases of OFD. However, in a more recent study the same group stated “that it is safe to treat these patients in a conservative manner with annual surveillance” [6].

In a large single-institution study [7] no patient with OFD (n = 42 f/u 38 to 300 months, average 118 months), or OFD-AD (n = 10 f/u 36 to 316 months, average 97 months) progressed to AD. Resection with clear margins was deemed necessary only for patients with classic AD. In a large multicenter study [8] OFD-AD (n = 117) showed aggressive behavior without metastatic potential; only one (histology proven) of the OFD-AD patients developed classic AD (histology proven) within the OFD-AD over a period of 29 years (no f/u reported). In this study AD (n = 141) showed full malignant potential with local recurrence (32%), metastases (18%) and fatal outcome (11%).

Three more patients have been described with transition from OFD-AD to AD, two by Hazelbag [9], one by Hatori [10].

We describe an additional case of OFD-AD of the tibia documented by repeated biopsies at ages 6, 8, 18, and 20 years, which developed into a classic AD within the OFD-AD at the age between 41 to 45 years. The case is of interest as it underlines the importance of “open-end” follow-up (f/u) for patients with the OFD-AD, and highlights the surgical techniques applied.

The female patient was born in 1975. The first biopsy of the tibia in 1981 revealed an OFD with elements suggesting OFD-AD. Repeat biopsies in 1983, 1984 and 1993 again showed OFD-AD and wide resection was recommended. At this time symptoms were limited to leg length discrepancy, requiring a shoelift on the opposite to compensate the 4 cm difference. Wedge osteotomy for correction of the procurvatum and shortening through the proximal part of the lesion (Figure 1) in 1995 healed uneventfully; the resected wedge was diagnosed again as OFD-AD. Postoperative imaging (MRI, X-Ray) remained unchanged until 2016 (Figure 2), the signal alterations even appeared to get smaller between 2005 and 2016. MRI in 2020 showed an enlarging osteolytic lesion within the preexisting diaphyseal changes with cortical erosion. FDG-PET-CT in 2020 (Figure 3) showed 5 metabolically active foci, the largest with a diameter of 17 mm, however without evidence of metastases; unfortunately earlier PET-CTs were not performed. CT-guided biopsy of the most active lesion was diagnosed again as OFD-AD and curetted. The curetted material however was found to contain a typical AD without dedifferentiation (Figure 4).

An extralesional resection of the involved 21 cm long diaphyseal tibial segment was performed; no elements of osteofibrous dysplasia or Adamantinoma were found in the pathologic examination of the periosteum and sections from the ends of the resected bone segment, indicating tumour free resection margins. The resected specimen was debrided and reamed (Figure 5). A slot to accommodate the transposed fibula was made. The tibial segment was pasteurized in 10% saline at 65˚C for 25 minutes according to Ji et al. [11] and replanted. For biologic reconstruction the ipsilateral fibula was transposed as a vascularized bone flap, retaining its proximal and distal vascular pedicle and inserted into the prepared slot in the pasteurized tibial autograft.

Skin slough developed distally and to avoid impending exposure of the reconstruction, radical soft tissue debridement was performed and the defect covered with a free microvascular gracilis muscle flap and split skin graft. Distally the fibula and pasteurized tibia fused primarily (Figure 6). Proximally autologous trabecular iliac bone graft at 9 months after the initial procedure led to fusion of

the proximal fibular stump to the proximal tibia (Figure 7 and Figure 8).

At 15 months after resection the patient is fully weight bearing. In a PET-CT there are neither active foci nor metastases.

This case adds to the four cases of the rare progression of osteofibrous dysplasia-like adamantinoma to classic adamantinoma hitherto reported [8] [9] [10]. The terminology “Osteofibrous dysplasia of the tibia and fibula” often is referred to as “Campanacci syndrome”. It frequently shows spontaneous regression and surgery should be delayed as any intervention may even activate progression. Morphologic features (particularly the shared presence of cytokeratin-positive cells) suggest the association with adamantinoma [12] [13] [14]. The terms differentiated Adamantinoma and OFD-AD are used synonymously [2]. “Classic” AD is a slowly developing malignant tumor with usually late appearance of metastases, whereas the dedifferentiated adamantinoma is a high grade malignant tumor with loss of epithelial differentiation and gain of sarcomatoid change [2].

Therefore patients affected by pathologic features in this spectrum present diagnostic and therapeutic challenges.

Our patient chose a biologic reconstruction. The procedure was planned in analogy to Capanna et al. [15], Lu et al. [16], Weichmann et al. [17] and Momeni et al. [18]. As an appropriate allograft was not available, the decision was made to replant the resected tibia after intraoperative external pasteurization for autologous biologic stabilization. Other options for tumor inactivation would have been external beam irradiation [19] or freezing in liquid nitrogen [20].

Before resection of the tibia diaphysis an external fixator was mounted to stabilize the leg during preparation of the fibula. The tibia was resected extraperiosteally at the predetermined level including the most distal changes (X-Ray, MRI, PET).

On a separate table the 21 cm long resected tibia segment was reamed, slotted and freed from all soft tissue. All removed tissue was examined pathologically. The removed periosteum was free of tumor, while the bone showed the OFD-AD and some islands of AD.

The prepared tibia (Figure 5) was then pasteurized at 65˚C for 30 minutes in 10% saline [11]. However, other authors used normal saline at 65˚ for 30 to 60 minutes [21] [22].

The vascularized fibula was mobilized in a classic fibula-pro-tibia technique. 6 cm of the distal fibula were spared to avoid ankle instability. In order to fit the fibula into the distal remaining tibia metaphysis and to attach the fibula to the retained proximal tibia diaphysis the resected/pasteurized tibia segment was shortened by 2 cm. The fibula could comfortably be inserted into the slot of the tibia. Osteosynthesis was performed using a standard LCP anteromedial tibia plate Depuy Synthes^Ò. The patient developed a distal skin slough, which needed debridement and the soft tissue defect was successfully reconstructed with a free microvascular M. gracilis flap. The clinical situation at 12 months postoperative is presented in Figure 9.

Besides the pathologic “diagnostic label” we are confronted with the need to assess and understand the biology in cases that fall within the spectrum including OFD, OFD-AD and AD. This case is of special interest because of the long-term f/u of an OFD-AD over 36 years and late transition into AD. The correct balance between careful observation and resection appears mandatory. We suggest to follow patients with OFD-AD indefinitely with imaging at long intervals and as soon as the patient notices any change of symptoms.

The study was approved by the institutional review boards.

The patient has been informed and agreed to submission of her case for publication. All details and radiographic images have been deidentified to protect patient confidentiality.

All authors have been involved in the treatment of the patient in a team approach. They contributed equally to the evaluation and interpretation of images and pathologic findings and finalizing the manuscript.

The authors declare no conflicts of interest regarding the publication of this paper.

Exner, G.U., Schai, P.A., Bühler, T.C., Kurrer, M.O. and Forster, N. (2022) Osteofibrous Dysplasia-Like Adamantinoma of the Tibia Diagnosed at Age 6 Years Progressing into a Classic Adamantinoma over 39 Years, Reconstruction Performed by a Modified Capanna Technique: A Case Report. Open Journal of Orthopedics, 12, 335-344. https://doi.org/10.4236/ojo.2022.127032