Proposed TNM-9 Classification for Salivary Gland Carcinoma
Huang SH, Cotler J, Palis B, Seethala RR, et al. Proposed Version Nine of the AJCC and UICC TNM Classification for Salivary Gland Carcinoma. JAMA Otolaryngology-Head & Neck Surgery 2026.
The Problem
The current TNM-8 N classification was designed for mucosal HNSCC, not salivary gland carcinoma. In over 7,600 SGC patients, N2a, N2c, and N3 each contained fewer than 50 patients (less than 1%). Survival among N2a, N2b, and N2c was poorly separated. Minor SGCs are staged by anatomic site rather than as a unified group. A disease-specific classification was overdue.
Study Design
Retrospective prognostic cohort study using the NCDB to derive a novel pTNM classification, validated in two independent datasets.
Derivation: 8,409 surgically treated major SGC patients (NCDB, 2012-2017). Median age 60 years. Median follow-up 88.4 months.
Validation 1: 1,015 major SGC patients from 4 international centers (Canada, Brazil).
Validation 2: 444 minor SGC patients from Memorial Sloan Kettering.
Primary endpoint: Overall survival
Why the Current N Classification Fails
pN0 | 5,748 (75.0%) | 87.1% |
pN1 | 533 (7.0%) | 66.6% |
pN2a | 48 (0.6%) | 49.0% |
pN2b | 1,283 (16.8%) | 46.0% |
pN2c | 21 (0.3%) | 56.7% |
pN3 | 26 (0.3%) | 38.5% |
N2a, N2c, and N3 are essentially nonexistent categories in SGC.
The Proposed pN Classification
pN0 | No positive LNs | 87.2% |
pN1 | 1-3 positive LNs without ENE | 66.1% |
pN2 | >3 positive LNs or any ENE-positive LNs | 43.1% |
6 categories reduced to 3, with clear survival separation and balanced sample sizes.
Proposed Stage Grouping
I | T1N0M0 | 1 (reference) | 93.1% |
II | T2N0M0 | 1.34 (1.11-1.61) | 89.2% |
IIIA | T1-2N1 or T3-4N0 | 2.36 (1.99-2.80) | 75.9% |
IIIB | T1-2N2 or T3-4N1-2 | 5.15 (4.38-6.06) | 46.6% |
IV | M1 disease | 13.61 (11.37-16.29) | 17.0% |
Key change: M0 cases confined to stages I-III. Stage IV reserved exclusively for M1 disease. This mirrors HPV-positive oropharyngeal and nasopharyngeal carcinoma staging.
T Classification
Largely unchanged. Definitions revised to apply to both major and minor SGC:
T1: Tumor 2 cm or smaller without extraparenchymal extension
T2: Tumor >2 cm and 4 cm or smaller without extraparenchymal extension
T3: Tumor >4 cm or gross extraparenchymal extension (major SGC only)
T4a: Invades immediately adjacent structures
T4b: Invades beyond adjacent structures
Minor SGC classified by size alone for T1-T3. Cortical bone erosion is NOT T4a.
Validation
International major SGC (n=1,015): 5-year OS: Stage I 95%, Stage II 92%, Stage IIIA 80%, Stage IIIB 41%. Worked in both WHO low-aggression and high-aggression subgroups.
MSKCC minor SGC (n=444): Clear separation across stages in both risk subtypes.
14 international experts achieved 100% consensus through a Delphi process.
Limitations
LN level/location (parotid vs cervical) not recorded in NCDB
OS used as endpoint, not disease-specific survival
Based on pathologic staging; clinical TNM applicability not yet validated
Minor SGC validation cohort relatively small (n=444)
Bottom Line
The proposed TNM-9 introduces the first SGC-specific staging system that unifies major and minor salivary gland carcinomas. The new pN replaces 6 poorly separating categories with 3 based on positive LN count (1-3 vs >3) and ENE status. Stage IV is reserved for M1 only.
For surgeons and pathologists: start reporting positive lymph node counts and ENE status systematically. These will be the key nodal prognostic factors in TNM-9.
Full Paper: 10.1001/jamaoto.2025.5396
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Krishnakumar Thankappan