This reference uses AJCC 8, confirmed current for this site on 4 November 2026. UICC TNM 9th edition, effective in 2026, is a separate system. Record the organisation, edition, anatomical location and c/p/yc/yp staging prefix. AJCC · UICC.
Use for primary malignant bone tumours after histological confirmation. Do not automatically apply bone-sarcoma staging to benign lesions, intermediate giant cell tumour of bone, skeletal metastases or multiple myeloma.
TNM for appendicular, trunk, skull and facial bone sarcomas
| Category | Definition | Clinical interpretation |
|---|---|---|
| T1 | Maximum tumour dimension up to and including 8 cm | Measure using appropriately staged cross-sectional imaging. |
| T2 | Tumour larger than 8 cm | Grade determines its prognostic group. |
| T3 | Discontinuous foci in the same primary bone (skip lesions) | Not synonymous with distant metastatic disease. |
| N0 / N1 | No / yes regional lymph-node involvement | Affects prognostic classification. |
| M0 / M1a / M1b | No distant disease / lung metastases / distant sites other than lung | Lung-only and extrapulmonary spread are grouped differently. |
| G1 / G2-G3 / GX | Low / higher / unassessable histological grade | Requires appropriate pathology review. |
AJCC 8 prognostic stage groups
| Stage | TNM and grade | Explanation |
|---|---|---|
| IA | T1 N0 M0 G1/GX | Localised lesion ≤8 cm, low or unassessable grade. |
| IB | T2/T3 N0 M0 G1/GX | Larger local lesion or discontinuous lesions in the same bone. |
| IIA | T1 N0 M0 G2/G3 | Higher-grade lesion ≤8 cm. |
| IIB | T2 N0 M0 G2/G3 | Higher-grade lesion >8 cm. |
| III | T3 N0 M0 G2/G3 | Discontinuous higher-grade disease in the primary bone. |
| IVA | Any T N0 M1a | Lung metastases without nodal spread. |
| IVB | Any T N1 any M; or M1b | Regional nodal disease or distant spread beyond lung. |
Pelvis and spine require site-specific T categories
For pelvic sarcomas, T depends on the 8 cm cut-off, pelvic segment involvement, extraosseous extension and major vessel involvement. Spinal T classification reflects vertebral segments, spinal-canal extension and adjacent vessels. The appendicular prognostic groups IA-IVB are not assigned to primary pelvic/spinal bone sarcoma in AJCC 8.
Pelvic bone sarcoma - anatomical T categories
The pelvic site is divided into four segments: lateral sacrum, iliac wing, acetabular/periacetabular region, and pubic rami/symphysis/ischium. The 8 cm cut-off is relevant for a/b subdivisions where indicated.
| T | Definition | Clinical interpretation |
|---|---|---|
| T1a | One pelvic segment, ≤8 cm, no extraosseous extension | Site and size both matter |
| T1b | One pelvic segment, >8 cm, no extraosseous extension | Size changes the subtype |
| T2a | ≤8 cm: one segment with extraosseous extension, or two adjacent segments without it | Assess extraosseous spread |
| T2b | >8 cm: one segment with extraosseous extension, or two adjacent segments without it | Size and extent must both be documented |
| T3a | ≤8 cm: two pelvic segments with extraosseous extension | Review the operative anatomy |
| T3b | >8 cm: two pelvic segments with extraosseous extension | Review vessels and neural structures |
| T4a | Three adjacent pelvic segments, or trans-sacroliliac spread reaching the sacral neural foramina | Locally extensive anatomical disease |
| T4b | Encasement of external iliac vessels or gross tumour thrombus in major pelvic vessels | Vascular resection implications |
Spinal bone sarcoma - segments and critical structures
Five anatomical vertebral segments are recognised: right pedicle, right portion of vertebral body, left portion of body, left pedicle and posterior elements. Segment count does not mean counting separate vertebrae.
| T | Definition | Clinical interpretation |
|---|---|---|
| T1 | One vertebral segment or two adjacent vertebral segments | Segments refer to anatomical vertebral portions |
| T2 | Three adjacent vertebral segments | Review cross-sectional imaging |
| T3 | Four adjacent vertebral segments | Not equivalent to four separate vertebrae |
| T4a | Tumour extends into the spinal canal | Assess neurologic compromise |
| T4b | Invasion of adjacent vessels or tumour thrombus within them | Vascular and surgical planning |
These are site-specific T categories; the extremity prognostic stage groups IA-IVB do not apply to primary pelvic or spinal bone sarcomas.
Giant cell tumour of bone may be described using Campanacci aggressiveness classification, not the AJCC malignant-bone-tumour stage grouping. Metastatic carcinoma in bone retains the classification of its primary tumour.
MDT minimum dataset
WHO entity, grade when appropriate, expert pathology verification.
Whole-compartment/whole-bone imaging when relevant, skip lesions, joint, vessels and nerves.
Chest CT and histology-specific work-up rather than a single generic pathway.
Sources: AJCC current staging system; NHS bone staging (TNM 8); NCI PDQ.
Other staging systems
Educational reference, not a substitute for specialist MDT review or official AJCC protocols. Record the edition used and do not infer a stage group from a single image.