Surface bone sarcomas: an update on current clinicopathological diagnosis and treatment

Abstract

Surface bone sarcomas are rare malignant bone tumours. Osseous and cartilaginous surface bone sarcomas are the most common, with parosteal and periosteal osteosarcomas, periosteal chondrosarcomas and secondary peripheral chondrosarcomas being the most frequent.Their clinical symptoms are non-specific and include pain for several months, swelling and limited range of motion of the adjacent joints.Prompt diagnosis is important, as biological behaviour, imaging and histopathologic characteristics, treatment and prognosis differ considerably from their conventional intramedullary counterparts. Moreover, their imaging characteristics are not infrequently non-characteristic and may be misinterpreted as juxtacortical benign lesions leading to incorrect diagnosis and treatment, with life-threatening repercussions. Molecular studies and histopathological sampling are essential for accurate diagnosis.There are still numerous issues regarding the biology, pathophysiology and treatment options of these entities due to their rarity. Cite this article: EFORT Open Rev 2021;6:905-917. DOI: 10.1302/2058-5241.6.210064.

Keywords: juxtacortical tumours; surface bone tumours.

Fig. 1

Parosteal osteosarcoma (PAO) in a 16-year-old female. (A) Lateral radiograph of the knee shows a typical PAO as a large, ossified opacity attached to the posterior cortex of the distal femoral metaphysis. Ossification is mainly central (B&C). Sagittal computerized tomography (CT) reformatted images (B: soft tissue window and C: bone window) exhibit with superior detail the thin separation between the tumour and the intact femoral cortex (‘cleft sign’ – thin arrow) as well as the ossified thick stuck (arrowhead). Lytic areas are seen within the ossified mass (black arrows) which is surrounded by a thick hypodense rim (arrows) representing cartilaginous tissue. (D) A fat-suppressed T2w magnetic resonance (MR) image shows the densely ossified stuck centrally (arrowheads) the inhomogenous moderately T2 hyperintense mass in the middle (asterisk), and the hyperintense cartilaginous component in the periphery (white arrows). There is no intramedullary extension of the tumour. (E) Intraoperative photograph of the popliteal fossa after the tumour resection. (F) Resected specimen.

Fig. 2

Parosteal osteosarcoma (PAO) in a 35-year-old female. (A) An X-ray of the right femur shows a smoothly marginated, ground glass density mass adjacent to the medial surface of the of the femoral diaphysis. The presence of the cleft sign inferiorly (thin arrow) and a densely ossified stuck centrally (arrow) help to differentiate this PAO from an atypical osteochondroma or the rare exophytic fibrous dysplasia and cortical osteoma. Benign periosteal reaction (buttressing) is seen in adjacent cortex (asterisk). (B) Transverse computerized tomography (CT) scan image confirms the presence of the broad, of cortical density stuck (arrowhead) and the cleft sign (thin arrows) that separates the ground glass mass (arrows) from the bone cortex. (C) The diaphyseal mass is mildly hypointense to muscles (arrows) on a coronal T1w magnetic resonance (MR) image. (D) On a coronal fat-suppressed T2w MR image the diaphyseal mass is inhomogenously hyperintense. The cortex remains intact with no medullary extension. (E) Intraoperative image of the posterior femur with the parosteal osteosarcoma. (F) The cortex of the posterior femur after tumour resection. (G) The resected specimen. (H) Postoperative radiographs of the femur after resection of the tumour and insertion of an intramedullary femoral nail.

Fig. 3

(A) Hematoxylin-eosin stain (X200): hypocellular tumour composed of mildly atypical spindle cells arranged in fascicles in desmoplastic collagenous stroma. The morphological findings are consistent with parosteal osteosarcoma (PAO). (B) MDM-2 (X400) and (C) CDK4 (X400): the majority of the neoplastic cells show strong nuclear positivity. (D) Hematoxylin-eosin stain (X200): excision specimen of the lesion shown in A, B and C: parallel trabeculae of well-formed woven bone with spindle neoplastic cells in loose stroma. (E) Hematoxylin-eosin stain (X40): the neoplastic population is characterized by mild cellularity and mild cellular atypia. (F) hematoxylin-eosin stain (X40): foci of moderate cellularity and moderate cellular atypia in PAO.

Fig. 4

Periosteal osteosarcoma in a 17-year-old female, presenting with a lytic process at the posterior aspect of the right femur as incidental finding. (A) An axial computerized tomography (CT) image shows a soft tissue mass extending from the posterior aspect of the right distal femur. The typical sunray mineralized spicules are seen within the mass. Distal aspect. (B) A sagittal (left) and an axial (right) fat-suppressed T2w magnetic resonance image show a lobulated, hyperintense mass adherent to the posterior aspect of the femur, with mild cortical erosion. The endosteal surface of the cortex and the medullary cavity appear normal. Source: With permission from Papagelopoulos PJ, Galanis E, Sim FH, Unni KK. Periosteal osteosarcoma. Orthopedics 1999;22:971–974.

Fig. 5

(A) A computerized tomography (CT) scan shows a cortical broad-based soft tissue mass (arrows) at the distal metaphysis of the left femur which surrounds about 50% of bone circumference. The tumour contains amorphous calcifications, and the adjacent cortex is thickened on this slice. (B, C) An axial (B) and a coronal (C) fat-suppressed T2w magnetic resonance (MR) image demonstrate the bulky tumour (arrows) originating at the medial site of the left femur. The tumour is moderately hyperintense and presents significant intramedullary extension (arrows). At the distal margin of the tumour on the coronal image the bone cortex looks thinned (C). The neurovascular bundle remains intact in B (thin arrow). Note that the calcifications are not apparent on MR images.

Fig. 6

(A) Hematoxylin-eosin stain (X100): low power view shows pleomorphic neoplastic population being adjacent to and invading bone. (B) Hematoxylin-eosin stain (X100) and (C) hematoxylin-eosin stain (X200): spindle neoplastic cells in close proximity with osteoid formation. (D) Hematoxylin-eosin stain (X400): on high power view, the neoplastic population shows high nuclear pleomorphism and numerous atypical mitoses. Given that the tumour mass is located on bone surface, the morphological findings are consistent with HGSO. (E) SATB2 (X200): the neoplastic cells show nuclear positivity. (F) Ki-67 (X200): proliferation index is high (~50%), consistent with the high mitotic rate. Note. HGSO, high-grade surface osteosarcoma.

Fig. 7

Periosteal chondrosarcoma (PCS) in a 17 year-old female. (A) Anteroposterior radiograph shows a broad-based soft tissue mass (arrows) at the proximal metadiaphysis of the of the left humerus, causing endosteal scalloping. (B&C) T1w coronal magnetic resonance (MR) image shows a mass (arrows) isointense to muscles (B) and hyperintense with a microlobular contour on a coronal fat-suppressed MR image (C). Cortex seems intact. There is a non-marginated area in the adjacent bone which is hypointense on T1w and hyperintense on fat-suppressed T2w image that corresponds to bone marrow oedema, as no malignant infiltration of the medulla was documented on pathology of the specimen (arrowheads). Barely seen punctuate and curvilinear calcifications at the periphery and within the mass (arrows) signifying cartilaginous matrix. (D&E) Intraoperative photographs showing the periosteal mass before (D) and after resection (E).

Fig. 8

A 42–year old man with abdominal discomfort and deteriorating left hip pain during the last six months. (A) frontal radiograph of the pelvis shows a bulky soft tissue mass (arrows) with typically cartilaginous rings and arcs calcifications, occupying the left pelvis. A densely mineralized lesion is seen at the left acetabular roof (arrowheads). (B) A computerized tomography (CT) image (bone window) shows an exostosis with lytic areas within it (arrow) of the left innominate bone protruding anteriorly and medially. A space-occupying soft tissue mass with calcified spots (arrows) seems to originate from the osseous protuberance and is displacing the adjacent left wall of the urinary bladder. (C) The mass is typically hyperintense on a fat-suppressed T2w axial image (arrows) and the calcifications are hypointense (arrowheads).

Fig. 9

(A) Hematoxylin-eosin stain (X40) and (B) hematoxylin-eosin stain (X100): the neoplastic population is composed of chondroblastic cells of moderate atypia widely invading bone cortex. (C) Hematoxylin-eosin stain (X100): the neoplastic cells extend to the adjacent soft tissue, invading skeletal muscle. (D) Hematoxylin-eosin stain (X200): on high power view, the chondroblastic neoplastic population is characterized by moderate cellularity and moderate atypia. Reactive bone formation on the grounds of periosteal reaction is noted on the left. Given that the tumour mass is located on bone surface, the morphological findings are consistent with PECS grade 2. Note. PECS, peripheral chondrosarcoma.