Chondrosarcoma — Grades & Surgery

Chondrosarcoma is the second most common primary malignant bone tumour after osteosarcoma. It is a malignant tumour of cartilage-producing cells and, critically, is largely resistant to conventional chemotherapy and radiotherapy — surgical resection is the primary and often only effective treatment. The grade of the tumour is the most important determinant of prognosis and drives the surgical strategy, from intralesional curettage for low-grade lesions to wide resection for high-grade disease.

• Epidemiology: peak incidence in the 4th–7th decade (adults and elderly, unlike osteosarcoma which peaks in adolescence); male predominance (1.5:1); most commonly affects the pelvis, proximal femur, proximal humerus, and ribs; the axial skeleton (pelvis and spine) accounts for approximately 40% of cases
• Classification by origin: primary chondrosarcoma (arises de novo in normal bone); secondary chondrosarcoma (arises in a pre-existing benign cartilage lesion — enchondroma or osteochondroma); secondary chondrosarcoma accounts for approximately 15–25% of cases; the risk of malignant transformation of a solitary enchondroma is very low (<1%), but in Ollier disease (multiple enchondromatosis) the risk is 25–30%, and in Maffucci syndrome (enchondromatosis + soft tissue haemangiomas) the risk is nearly 100% and may involve multiple simultaneous chondrosarcomas
• Histological subtypes: conventional (hyaline cartilage — the most common; Grades 1–3); dedifferentiated (high-grade non-cartilaginous component superimposed on a low-grade chondrosarcoma — very aggressive; accounts for ~10%; poor prognosis); clear cell (low-grade; affects the epiphysis of long bones; rare); mesenchymal (very aggressive; responds better to chemotherapy than other subtypes)

• History: deep, dull, aching pain — often present for months to years before diagnosis (Grade 1 chondrosarcomas are slow-growing and symptoms may be subtle); night pain and rest pain are features of higher-grade lesions; a swelling may be palpable for peripheral lesions; a previously asymptomatic enchondroma becoming painful warrants imaging reassessment for malignant transformation
• Plain radiographs: the initial investigation; typical features — lytic lesion with endosteal scalloping (scalloping of the inner cortical surface due to cartilage lobules pressing on the cortex); `rings and arcs` calcification pattern (curvilinear calcification within the cartilage matrix — highly characteristic of cartilaginous tumours); cortical thickening or expansion; `popcorn` calcification; cortical destruction and soft tissue extension indicate higher grade; periosteal reaction is less common in chondrosarcoma than osteosarcoma; the pelvis and proximal femur are the most common sites on X-ray
• MRI: best imaging for soft tissue extent, cortical breakthrough, and intramedullary extent; cartilaginous lesions are characteristically bright on T2 (high water content in chondroid matrix); MRI distinguishes enchondroma (usually <5 cm, peripheral, no soft tissue mass, no cortical destruction) from chondrosarcoma (larger, deep endosteal scalloping >2/3 cortical thickness, soft tissue mass, cortical destruction); MRI also defines the surgical resection margin
• CT scan: best for cortical integrity, calcification pattern characterisation, and chest staging (lung metastases — the primary site of distant spread)
• Biopsy considerations: Grade 1 vs Grade 2 distinction is the most difficult in pathology — there is significant interobserver variability; molecular markers (IDH1/IDH2 mutations — present in ~50% of conventional chondrosarcomas and most enchondromas; the same mutation does not reliably distinguish benign from malignant) are increasingly used; biopsy must be performed in a specialist centre using the Enneking/Mankin biopsy principles to avoid contaminating the surgical field

• Grade 1 chondrosarcoma — intralesional curettage: for Grade 1 lesions in accessible locations (distal femur, proximal humerus, tibia, hand, foot); the lesion is curetted thoroughly; adjuvants are applied to the cavity wall — phenol (chemical adjuvant; burns residual tumour cells; causes local soft tissue toxicity — must be used carefully), argon beam coagulation, or cryotherapy (liquid nitrogen); the cavity is then filled with bone cement (PMMA — which also provides a `heat kill` effect as it polymerises) or bone graft; local recurrence after curettage of Grade 1 chondrosarcoma is approximately 10–20%; if local recurrence occurs after intralesional surgery, wide resection is then required
• Grade 2–3 chondrosarcoma — wide resection: wide surgical margins are mandatory for Grades 2 and 3; the tumour is resected en bloc with a cuff of normal tissue; reconstruction depends on location — mega-prosthesis for distal femur/proximal tibia/proximal humerus; pelvic resection (hemipelvectomy) for large pelvic chondrosarcomas; rib resection + chest wall reconstruction; expendable bones (fibula, clavicle) can be excised without reconstruction; pelvic resections carry significant morbidity and high complication rates
• Pelvic chondrosarcoma: one of the most surgically challenging presentations; the ilium, acetabulum, pubis, and ischium may all be involved; internal hemipelvectomy (resection of the pelvic ring while preserving the limb) or external hemipelvectomy (amputation of the entire limb + pelvis); functional outcomes after major pelvic resection are poor; multi-disciplinary planning is essential
• Radiotherapy and chemoradiotherapy: conventional chondrosarcoma is generally considered radio-resistant; proton beam or heavy ion radiotherapy (available in specialist centres) achieves better local control for skull base and spinal chondrosarcomas where surgical margins are limited; dedifferentiated chondrosarcoma may be treated with chemotherapy targeting the high-grade component

• The Grade 1 vs Grade 2 dilemma: the distinction between a Grade 1 chondrosarcoma (amenable to intralesional curettage) and a Grade 2 (requires wide resection) is the most clinically consequential decision in chondrosarcoma management; Grade 1 and 2 lesions exist on a histological continuum and interobserver variability between pathologists is significant; clinical and radiological features (size, location, endosteal scalloping depth, cortical destruction) must be integrated with histology; in equivocal cases, the safer oncological approach is wide resection; the risk of under-grading and performing curettage on a Grade 2 lesion is local recurrence with potential grade progression on recurrence
• IDH1/IDH2 mutations in chondrosarcoma: IDH1 and IDH2 mutations (isocitrate dehydrogenase) are found in approximately 50–70% of conventional chondrosarcomas and in most central enchondromas; the same mutations are present in both benign and malignant cartilaginous tumours, so their presence does not distinguish malignancy; however, IDH inhibitors (ivosidenib for IDH1; enasidenib for IDH2) are being investigated as targeted systemic therapies for advanced/metastatic chondrosarcoma in patients with IDH mutations — this is an active area of clinical trials; IDH mutation testing is now routinely performed in chondrosarcoma diagnosis
• Atypical cartilaginous tumour (ACT) vs Grade 1 chondrosarcoma: the current WHO classification uses `atypical cartilaginous tumour` (ACT) for Grade 1 cartilaginous lesions of the appendicular skeleton (long bones), reserving `Grade 1 chondrosarcoma` for lesions of the axial skeleton (pelvis, spine, ribs); this terminology reflects the very low metastatic potential of appendicular Grade 1 lesions (which essentially never metastasise) vs axial Grade 1 lesions (which have higher local recurrence and occasional metastatic potential); the distinction is of clinical relevance when counselling patients about prognosis and the acceptability of intralesional surgery

• Chondrosarcoma: 2nd most common primary malignant bone tumour; adults/elderly; pelvis + proximal femur most common sites; resistant to chemotherapy and radiotherapy — surgery is the primary treatment
• Rings and arcs calcification + endosteal scalloping on X-ray: characteristic of cartilaginous tumours; deep scalloping (>2/3 cortical thickness) suggests malignancy
• Evans grading: Grade 1 (~90% 5-year survival) — intralesional curettage + adjuvants; Grade 2 (~60–70%) + Grade 3 (~30–40%) — wide resection; dedifferentiated (~10–25%) — wide resection + chemotherapy
• Chemo/radio resistance: conventional chondrosarcoma is largely resistant; proton beam for skull base/spinal lesions; dedifferentiated component responds to MAP chemotherapy (osteosarcoma protocol)
• Grade 1 curettage adjuvants: phenol (chemical kill), argon beam coagulation, cryotherapy; fill with PMMA cement (heat kill on polymerisation); 10–20% local recurrence rate after intralesional curettage
• Grade 1 vs Grade 2 dilemma: most important clinical decision; interobserver variability in pathology; integrate radiology (endosteal scalloping, cortical destruction, size) + histology; err toward wide resection if equivocal
• Secondary chondrosarcoma: from enchondroma or osteochondroma; Ollier disease — 25–30% malignant transformation risk; Maffucci syndrome — near 100% risk
• ACT (atypical cartilaginous tumour): WHO term for Grade 1 in appendicular skeleton; essentially never metastasises; intralesional curettage acceptable; Grade 1 in axial skeleton = `chondrosarcoma` with higher risk
• IDH1/IDH2 mutations: ~50–70% of conventional chondrosarcomas; also in enchondromas — does NOT distinguish benign from malignant; IDH inhibitors in clinical trials for advanced disease
• Pelvic chondrosarcoma: most surgically challenging; internal or external hemipelvectomy; high morbidity; multidisciplinary planning essential