Introduction

Chondroblastoma (CB) is a rare benign tumor that accounts for <1% of all primary bone tumors [1]. It may affect every bone and patients most commonly at their second decade of life [2, 3]. Clinical presentation typically consists of gradually increasing pain and local tenderness, followed by swelling and limitation of movement of the adjacent joint [3]. Surgery is the mainstay of treatment for CB; curettage with or without local adjuvants (phenol) and bone grafting/cement, or cryosurgery is the techniques most frequently described [3,4,5,6]. The rate of recurrence after these procedures has been reported to be between 10 and 35% [4,5,6]. To the best of our knowledge, the literature is lacking information on CB in adult age; review of five textbooks on bone tumors [3, 4, 7,8,9] showed that patients age ranges from 2 to 83 years, but all mentioned that most CB is seen in patients aged 10–20 years. Additionally, in our own clinical practice we have observed some differences concerning type of bone involvement and biological behavior of these tumors in adults compared to children and adolescents. Therefore, we perform this study to report the characteristics of CB in adults of more than 30 years of age and to discuss the clinical and imaging findings, type of treatment, oncologic and functional outcomes of CB in this age group. We believe that our findings would be useful for the related literature on bone tumors.

Materials and methods

After institutional review boards and ethics committee approval was obtained, we retrospectively studied all patients with histologically documented CB treated at our institution from January 1981 to December 2014. Inclusion criterion was patients aged 30 years at diagnosis or older. Twenty-three patients with a minimum follow-up of 2 years were included in this study. All pathology materials and imaging studies for these patients were evaluated for their distribution in the patient cohort and for possible correlations with outcome. Data were collected by reviewing the medical records, radiographs and pathologic reports. Stage was assessed according to Enneking classification for benign tumors. Routine clinical and radiographic follow-up evaluation was performed every 6 months for the first 2 years and then annually. All information was recalled from the tumor registry; no patient was specifically recalled for the purpose of this study. The occurrence of local recurrence or death was recorded.

Functional outcome was assessed for patients with tumors affecting lower limb, using the Musculoskeletal Tumor Society (MSTS) functional rating system. This system uses a 30-point scale to equally weight each of six parameters, including pain, functional limitation, walking distance, use of support, emotional acceptance and gait.

Data were recorded in a Microsoft Excel® 2003 spreadsheet (Microsoft Inc, Redmond, WA) for further evaluation. Additionally, a systematic search of the literature was done to identify studies reporting on patients beyond their 30 years of age with the diagnosis and treatment for CB. English and non-English language papers were searched in Pubmed using the «MeSH» chondroblastoma with and without the terms «age», «treatment», «adult» or «recurrence», and in ISI Web of Knowledge database searching «chondroblastoma» as topic. The search was done using the literature from 1970 to date. The focus of each reference varied including: series of patients with CB irrespective of locations, case reports and articles investigating specific forms of treatment of CB.

Results

There were 15 males (65%) and 8 females (35%) with a mean age of 40 years (range 30–59 years) (Fig. 1). Compared to our institutions total number of patients with CB diagnosed and treated within the same time period of the study, this accounted in patients older than 30 years of age for 7%. Tumor involved the long bones in eight patients (35%): femur in 4 (one in the greater trochanter), humerus in 3 and proximal tibia in 1 patient. Other sites were talus (five patients), calcaneus (three patients), acromion (two patients) and cuneiform, metatarsus, scapula, posterior arch of L4 vertebra and periacetabulum (one patient each). Pain was the most common presenting symptom, followed by pain and swelling (one patient with a CB of the metatarsals) and pathologic fracture (one patient with a CB of the scapula) (Fig. 2). The mean duration of symptoms was 14 months; one patient with a humeral CB reported experience of pain for 8 years.

Fig. 1
figure 1

A graph shows the age at diagnosis of the 23 adults patients with CB included in the present study

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Fig. 2
figure 2

Lateral view of the scapula of a 38-year-old man with CB of the blade of the scapula presenting with a pathologic fracture

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The common radiographic finding was a radiolucent lesion with a well-defined margin; partial ill-defined margins were observed in eight patients. Fine sclerotic rim was found in six patients and a fine calcification in two patients. Periosteal reaction was rarely observed (two patients), whereas cortical break was observed in four patients: one patient with CB at the posterior vertebral column, and three patients with osteolysis of the subchondral bone and articular involvement. The acromial CB showed a circumferential cortical expansion (Fig. 3a). In the long bones, CB was equally located at both ends of the bone (Fig. 3b).

Fig. 3
figure 3

a Anteroposterior radiograph of the right shoulder of a 53-year-old woman with CB of the acromion. b Sagittal CT of the knee of a 36-year-old man with a distal femoral CB

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Nine patients underwent a trocar-needle biopsy; in two of them, a repeat biopsy was necessary because of a non-diagnostic initial biopsy sample: One femoral CB was diagnosed by frozen section and a humeral CB by open incisional biopsy. Three patients underwent an incisional biopsy and eight cases just a frozen section during main surgery. Because of typical imaging findings suggesting with certainty the diagnosis of CB, a biopsy was not done preoperatively in the remaining three patients (humerus, calcaneum, lumbar spine tumors); in these patients, the diagnosis of CB was documented histologically in the postoperative tumor specimen. In two patients (a calcaneal CB and a periacetabular CB), a secondary aneurysmal bone cyst (ABC) was observed, and in 1 patient a cystic variant of CB was observed.

Treatment consists of curettage only in six cases, curettage plus phenol as local adjuvant in 13 cases, curettage and radiotherapy in a patient with vertebral CB that underwent a previous laminectomy for canal stenosis in another hospital, resection in two cases with acromial CB and chopart amputation in a patient with metatarsal CB because of local recurrence after an inadequate excision in another hospital. After curettage, the bone defect was filled with acrylic bone cement in seven patients, bone allograft in four patients, subchondral bone allograft plus cement in another patient and nothing in the remaining eight patients. None of the patients received chemotherapy.

At a mean follow-up of 8.4 years (range 3–30 years), twenty patients (87%) remained continuously local recurrence-free, whereas three experience local recurrences (13%). One patient with a humeral CB experienced a first local recurrence 26 months after curettage and cement, a second recurrence 16 months later treated with repeat curettage, phenol and cement, and two soft tissue recurrences 20 and 16 months later treated by surgical excision. This patient is local recurrence-free at last follow-up for the purpose of this study, 44 months after her last local recurrence. Another patient experienced a local recurrence 2 years after curettage, phenol, subchondral bone grafting and cementation of a proximal tibial CB (Fig. 4a, b), treated with repeat curettage. Fifteen months later he experienced a second local recurrence that was finally treated by resection of the proximal tibia and reconstruction with an allograft prosthetic composite (Fig. 4c). A third patient with a periacetabular CB experienced a local recurrence three months after a curettage plus phenol and cement and was treated with repeat curettage. No patient of this series experienced metastases within the period of this study.

Fig. 4
figure 4

Proximal tibia CB in a 36-year-old man. a Anteroposterior radiograph of the left knee of a 36-year-old man with a proximal tibial CB shows an atypical appearance with granules of tenuous, fading radio-densities and some calcifications. b Anteroposterior radiograph of the left knee (same patient) 2 years after surgical treatment (curettage, phenol, subchondral bone grafting and cementation) shows local recurrence. c Fifteen months later the patient experienced a second local recurrence that was finally treated with resection of the proximal tibia and reconstruction with an allograft prosthetic composite

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Two patients experienced major complications. One patient experienced a post-radiation sarcoma of the spine 11 years after radiotherapy for a vertebral CB, and one patient experienced ulnar nerve neuropathy and humeral internal rotation deficiency after five surgical treatments for a humeral CB due to multiple local recurrences. Four patients experienced minor complications including chondropathy of the subtalar joint after calcaneus curettage and cementation for a calcaneal CB, pain on long-time walking after curettage for another calcaneal CB, supraspinatus tendinitis after resection for an acromial CB and algodystrophy after curettage for a talar CB.

About functional results, all patients except those with complications experienced partial to complete pain relief. Most of the patients with CB of the lower limb were able to walk without functional limitation, with a mean MSTS functional outcome score of 26 (range 17–30).

Discussion

A systematic literature search showed 474 cases of CB in all age groups; the prevalence of CB in patients older than 30 years of age was about one-tenth of all CB cases (45 patients; Table 1) [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. In the present study, we reported the clinical and imaging findings, treatments and follow-up of 23 adults with CB; 19 patients (56%) were 30–40 years of age and 4 patients (17%) were more than 50 years of age. This underlines that the incidence of CB is inversely proportional with the age of the patients; however, age should not be considered a prognostic factor for this benign tumor. Additionally, there were no correlations between age of the patients and gender (twice common in male than in female patients), pain, imaging appearance, association with secondary ABC and incidence of local recurrences. Typically, CB involves the epiphyses of the long bones; however, in the present series in adults, the tumors involved more commonly in the flat and short tubular bones of the foot, especially the talus and calcaneus. Patients with CB of the skull tend to be older than those with CB of the long bones, with a mean age of 44 years [1]. Bloem et al. [11] studied 104 patients with CB and reported that 80% of CB involved the long bones with a mean patients’ age of 16 years, whereas 20% of CB involved the flat and short tubular bones of the hand and foot, most commonly the calcaneus and talus with a mean patients’ age of 28 years. Also, Turcotte et al. [12] reported a higher occurrence of flat bone CB in older patients. The results of our study confirm these previous reports.

Table 1 Summary of the published studies reporting on adult patients with CB
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Treatment consisted of curettage only (6 cases), curettage plus phenol (13 cases), curettage plus radiotherapy (one patient with vertebral tumor), resection (two patients with CB of the acromion) and chopart amputation (one patient with a metatarsal tumor).

Suneja et al. [1] reported a large series of CB in which meticulous curettage alone was curative in most of the cases. In our series, six patients were treated with curettage without local adjuvants and none of them experienced a local recurrence. Conversely, all our patients with local recurrence received adjuvant treatments including phenol and/or cement. In CB in adults, we did not find any relation between the type of treatment and local recurrence; however, considering that there was heterogeneity of treatments over the years, this should be considered a limitation of our study. Because of the short time between the occurrence of a local recurrence and index surgery (3 months) in the patient with the periacetabular CB, we believe that local recurrence in this patient should be attributed to inadequate curettage of the primary tumor. This should probably explain the local recurrence in the patient with a proximal tibia CB; in this patient, the tumor was located beneath the tibia plateau that precluded complete excision of the tumor without damage of the articular cartilage.

One of the most important differential diagnosis for CB, especially in patients older than 30 years, is clear cell chondrosarcoma [3, 7], which is a rare low-grade bone sarcoma that accounts for approximately 1–2% of all CB cases and 0.2% of all primary bone tumors [25, 26]. Imaging findings on radiographs and size can be similar between these two lytic bone lesions. Imaging features that suggest clear cell chondrosarcoma as opposed to CB include the lack of surrounding edema and high signal intensity on T2-weighted MR images. In contrast, the majority of CB show low-to-intermediate signal intensity in all MR imaging sequences in the solid non-cystic component of the tumor [25]. If any doubt on imaging studies, biopsy for histological diagnosis is necessary. Because of the malignant biological behavior of clear cell chondrosarcoma, curettage, as for CB, is not a suitable treatment as it invariably leads to local recurrence [25]. Instead, wide resection is the treatment of choice for this chemo- and radio-resistant sarcoma [7, 26].

Conclusion

Our analysis of a cohort of adult patients with CB showed that CB in this age group involves more commonly the flat and short tubular bones of the foot, especially the talus and calcaneus, as opposed to the long tubular bones. Imaging findings, treatment and outcome of CB in this age group are similar to those affecting younger patients.