Chondroblastoma-like osteosarcoma: a case report and review

Skeletal Radiol DOI 10.1007/s00256-014-2068-2

CASE REPORT

Chondroblastoma-like osteosarcoma: a case report and review Osman Emre Aycan & Daniel Vanel & Alberto Righi & Yavuz Arikan & Marco Manfrini

Received: 14 May 2014 / Revised: 11 November 2014 / Accepted: 17 November 2014 # ISS 2014

Abstract Chondroblastoma-like osteosarcomas are extremely rare malignancies having varying clinical, radiological and histological features. Their rarity causes challenges in both diagnosis and clinical management. They are often misdiagnosed as benign lesions. Their accurate diagnosis is important because they require adequate treatment. Misdiagnosed lesions or undertreatment may result in recurrences. We report a case of chondroblastoma-like osteosarcoma arising in the left first metatarsal bone with tarsometatarsal joint involvement in a 10-year-old boy for whom surgery with an original technique was planned after a multidisciplinary diagnostic review. Keywords Chondroblastoma like osteosarcoma . Chondroblastoma . Osteosarcoma of the foot

Introduction Osteosarcoma is the most common primary malignant tumor of bone in the first 3 decades of life. The term osteosarcoma, indeed, represents a group of rare malignancies that produces either osteoid or woven bone, with multiple histological and anatomical variants [1–3]. Chondroblastoma-like osteosarcoma, which has distinct clinical and histological features, is an extremely rare entity constituting less than 1 % of osteosarcomas. Although the relevant literature only includes case reports and small case series, chondroblastoma-like osteosarcoma have O. E. Aycan : Y. Arikan : M. Manfrini Department of Musculoskeletal Oncology, Istituto Ortopedico Rizzoli, Via Pupilli 1, 40136 Bologna, Italy D. Vanel (*) : A. Righi Department of Pathology, Istituto Ortopedico Rizzoli, Via Pupilli 1, 40136 Bologna, Italy e-mail: [email protected]

a mild tendency to appear in young adults, often involving the bones of the foot [4–6]. To our knowledge no case has been reported in childhood. We have reviewed the literature and reported a child patient with this exceptional malignancy of bone, which illustrates our experience with a challenging diagnosis and surgical treatment.

Case report A 10-year-old Caucasian male patient presented with pain in the medial part of left foot for 20 days, which was triggered by physical activity. There was no history of chronic disease, and physical examination revealed no swelling or neurovascular deficit. Anteroposterior and lateral radiographs of the left foot demonstrated a lytic lesion, which caused mild expansile remodeling of the entire first metatarsal with internal septations and a partial peripheral rim of sclerosis. The distal epiphysis of first metatarsal remained unaffected. The pattern was consistent with an aneurysmal bone cyst (ABC) or a giant cell tumor of bone, but the age of the patient was less consistent with the latter possibility (Fig. 1). Magnetic resonance (MRI) study showed a large area of bone marrow replacement in the left first metatarsal bone hypointense on T1-weighted sequences (Fig. 2a), heterogeneous-hyperintense on STIR (Fig. 2b) and contrast enhancement (Fig. 2c). The cortical bone was globally thinned but still intact, and the distal epiphysis was normal. There was limited edema around the bone. There was an effusion at the first tarsometatarsal joint, whereas the first metatarsophalangeal joint remained unaffected. There was no evident soft tissue mass. A needle biopsy was performed. Histologically, the lesion consisted of a proliferation of small cells with moderate amounts of eosinophilic cytoplasm and irregular, grooved

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Fig. 1 Anteroposterior radiographs of the left foot. There is a central predominantly lytic lesion with partially sclerotic margins and expansile remodeling in the first metatarsal. The distal epiphysis and metacarpophalangeal joint are unaffected; however, the proximal epiphysis is involved

and cleaved nuclei with moderate cytological atypia and foci of necrosis. Scattered giant cells were present. The lesion suggested a differential diagnosis between a chondroblastoma and a low-grade chondroblastoma-like osteosarcoma, which was the favored diagnosis after multidisciplinary discussion. Taking into account of patients’ age and unaffected first metatarsophalangeal joint, resection of the first metatarsal bone, removal of the affected tarsometatarsal joint, sparing the unaffected distal epiphysis, and reconstruction with a fibular autograft were planned. Chemotherapy was not planned because of the low-grade malignancy. The surgical specimen was 6 cm long, including a section from the distal portion of the medial cuneiform and the growth plate from the head of the first metatarsal. A 12-cm fibular autograft was divided into two segments of equal length and embedded between the remaining medial cuneiform and the residual subchondral head of the first metatarsal bone without a fixation device.

Fig. 2 a On the T1-weighted sequence almost all the first metatarsal bone is occupied by a hypointense lesion leaving only the distal epiphysis and partially proximal epiphysis free. b On the T2-weighted fat presaturated sequence the lesion is heterogeneous and hyperintense with partial edema of the plantar soft tissues proximally. c After contrast medium injection heterogenous enhancement of the lesion and peripheral edema are seen

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On histology, the resected first metatarsal specimen exhibited a neoplastic proliferation with the same features as the previous needle biopsy with an infiltrative growth pattern toward the soft tissues and host bone trabeculae (Fig. 3a). Moderate anaplasia of the tumoral cells was noted along with chondro-osteoid matrix (Fig. 3b). A neoplastic vascular invasion was also observed (Fig. 3c). The diagnosis of low-grade chondroblastoma-like osteosarcoma was confirmed. The histological report confirmed a wide, tumor-free margin all over the specimen besides the distal margin toward the epiphysis where the margin was rated as marginal. Neither neurovascular deficits nor surgical site complications developed in the early postoperative period. At the 6th month, radiographs revealed good bone graft osteointegration at both the proximal and distal ends. Chest CT was normal.

Discussion Osteosarcomas represent the most common primary malignancy of bone in children and young adults [1–3]. Chondroblastoma-like osteosarcoma, whose name was initially defined by Schajowicz et al. in 1990, is an extremely rare histological variant of osteosarcoma, which was reported in rare case reports and series [4–7]. The vast majority of the reported lesions were seen at the 3rd decade. Common sites of involvement include the metatarsal bones (4), femur (3), ribs (3), humerus (2), tibia (2) and single cases at the talus, phalanx, fibula, ischium and ilium [4–8]. When compared to previous case reports and series, our 10-year-old patient represents the youngest case affected by this diagnosis [4–7]. Reported chondroblastoma-like osteosarcoma patients were referred with a painless mass or pain following a minor trauma [4–7]. The pain in our case was triggered by physical activity. Chondroblastoma-like osteosarcomas are reported at various locations and patterns. Although in the first chondroblastoma-like osteosarcoma report the lesion was radiologically described as a diaphyseal lesion with a slightly expansile radiolucent area, causing endosteal scalloping and laminar periosteal reaction, following reports defined an expansile lesion with a mixed pattern of both sclerotic and lytic areas with either thin or absent cortices and focal punctate calcifications [4, 5]. Destructive permeation of the host bone, soft tissue involvement and poorly defined borders are also radiologically described [6, 7]. The radiographic features of our case resemble those in a case reported by Bacchini et al. [5]. Previous reports defined chondroblastoma-like osteosarcoma radiographically as a lytic, expansile lesion with endosteal erosions and focal punctate calcifications.

Fig. 3 a,b and c Low-power magnification on H&E shows the infiltration of the neoplastic cells (asterisk) into the soft tissues (a, magnification 10×). Medium-power magnification reveals hyperchromatic cells (arrow) with bone production and scattered giant cells (b, magnification 100×). Note the neoplastic vascular invasion (arrow) (c, magnification 250×)

Metatarsal involvements were reported to affect the whole bone. Thus, the differential diagnosis may inc l u d e A B C [ 9 – 11 ] , g i a nt ce l l t um o r [ 9 , 1 0 ] , chondromyxoid fibroma [12], chondroblastoma,

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Langerhans cell histiocystosis [9], fibrous dysplasia and Ewing’s sarcoma [13], osteosarcoma [14] and chondrosarcoma [15, 16] from a radiographic point of view. Osteosarcomas of the hands or feet are rare. In a series of 40 osteosarcomas of the hands and feet, distribution in the foot was tarsal bones 56 %, metatarsal bones 33 % and phalanges 11 %, and 71 % of the lesions were high grade [14]. Lytic osteosarcomas rarely have a specific radiological pattern in the foot [8, 14]. We found no MRI or CT study of chondroblastoma-like osteosarcomas [4–6]. Our lesion was hypointense on T1weighted sequences and heterogeneous and hyperintense on T2FS sequences, with heterogeneous contrast enhancement. No fluid levels were visible. Chondroblastomas, which mostly resemble chondroblastoma-like osteosarcoma, are benign cartilageproducing neoplasms that commonly affect the epiphysis of long bones [1]. Although the reported age is widely distributed, the vast majority of cases are in the 2nd decade. Radiologically chondroblastomas are well defined, oval to round, eccentric lesions with or without sclerotic borders [1, 17–24]. Cortical expansion with erosion and periosteal reactions may be seen but are unusual. MRI may reveal an extensive edema surrounding the lesion [11, 24]. The vast majority of chondroblastomas (approximately 75 %) may show variable (low to intermediate) intensity on T2weighted images; however, signal intensity on T1- and T2weighted MR images and the patterns of contrast enhancement in chondroblastoma are reported to be dependent on ratios of the immature chondroid matrix, cellularity of chondroblasts, calcifications, hemosiderin and aneurysmal bone cyst components [25, 26]. The conventional treatment includes intralesional curettage and grafting; besides, radiofrequency ablation was recently reported to be an alternative treatment modality in selected cases [17, 23–27]. The literature also indicates malignant transformation of benign chondroblastoma after radiation therapy [17, 21, 22]. In our case the epiphysis is mainly spared, which should have put some doubts on the diagnosis of chondroblastoma. The terms “aggressive chondroblastoma,” “malignant chondroblastoma” and “metastatic chondroblastoma” indicate a histologically benign chondroblastoma, but long-term follow-up of these lesions is associated with increased local recurrence rates, clinical aggressiveness and even metastasis [20–22]. The histological evaluation of some reported distant metastatic lesions may exhibit the same benign chondroblastoma tissue; thus, authors have concluded that these metastases might be secondary to iatrogenic "seeding" of vessels due to vigorous curettage [20]. Most of the lung metastases or recurrences in case reports related to aggressive, malignant or metastatic chondroblastoma occurred after resection of the tumor [17].

Characteristic histopathological features of chondroblastoma-like osteosarcoma are focal tumoral necrosis, suspicious neoplastic microemboli, anaplasia of cells associated with a high number of mitotic figures (>10 per high power fields), focal osteoid production (bone formation) and a permeation pattern with infiltration of soft tissue at the bone neoplasm margin [5]. Similar histological diagnostic patterns might be encountered in chondroblastoma. Histologically, chondroblastoma has round to polygonal cells with welldefined cytoplasmic borders and a round-to-ovoid nucleus. Osteoclastic giant cells can always be seen; “chicken wire” calcification is common, but hyaline cartilage is uncommon. Individually chondroblasts may show atypia, but this is not related to the prognosis. Mitoses are observed, but atypical forms are never seen [1].

Conclusion Chondroblastoma-like osteosarcomas are extremely rare malignancies with variable clinical, radiological and histological features. The differential diagnosis of chondroblastoma-like osteosarcoma may be confusing clinically and radiologically. When a chondroblastoma with an unusual and aggressive radiologic pattern is encountered, this rare malignancy should always be considered.

Conflict of interest The authors of this case report declare no conflict of interest.

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