15.6 SEER Summary Stage 2018: Codes, Timing, General Rules & Site Examples
Key Takeaways
SS2018 codes are 0 in situ, 1 localized, 2 regional by direct extension only, 3 regional lymph nodes only, 4 regional by both, 7 distant, 8 benign or borderline (brain and CNS chapters only), and 9 unknown.
Summary Stage includes all information within four months of diagnosis without disease progression, or through completion of first-course surgery, whichever is longer; progression after the initial workup is excluded.
Tumor size does not affect Summary Stage, unknown lymph node status is treated as no involvement, and positive regional nodes (Regional Nodes Positive 01–90, 95, 97) require code 3, 4 or 7.
After neoadjuvant treatment, surgical findings are used only if they show more extensive disease than the pre-treatment clinical findings.
Death certificate only cases and unknown primaries (C809) are always 9; melanoma in-transit, satellite and microsatellite metastases count as positive nodes (code 3); leukemias and plasma cell myeloma are 7.
Why Summary Stage exists
Summary Stage is the simplest way to compare stage across all cancers, across time, and between hospital and population registries. It is based on anatomic extent only and applies to every primary site and histology. Many chapters are defined by site, some by histology, and some by both. SS2018 chapters follow AJCC 8th edition concepts and, from 2021, the AJCC Version 9 updates, but the two systems differ. Something regional in AJCC can be distant in Summary Stage. If a structure or node is not listed under codes 1–4, check code 7.
The codes
| Code | Meaning |
|---|---|
| 0 | In situ, intraepithelial, noninvasive |
| 1 | Localized only (confined to the organ of origin) |
| 2 | Regional by direct extension only |
| 3 | Regional lymph node(s) only |
| 4 | Regional by both direct extension and lymph nodes (2 + 3) |
| 7 | Distant site(s) or distant lymph node(s) |
| 8 | Benign or borderline: only for the Brain, CNS Other, Intracranial Gland and (2023+) Medulloblastoma chapters |
| 9 | Unknown if extension or metastasis (unstaged) |
The code is hierarchical: when more than one applies, use the highest.
Time frame
"Summary Stage should include all information available within four months of diagnosis in the absence of disease progression or upon completion of surgery(ies) in first course of treatment, whichever is longer."
Disease progression, including metastases, known to have developed after the initial staging workup is excluded.
General rules
- Combined assessment: code from clinical and operative or pathological information together. Gross findings at surgery matter when tumor cannot be removed. If the pathology and operative reports disagree about excised tissue, the pathology report has priority. If the pathology disproves a clinical finding, use the pathology.
- Tumor size does not affect Summary Stage. For most chapters, SSDIs do not either.
- Unknown primary extent: if regional nodes are positive but the primary's extent is unknown, default to 3. If distant metastasis is present, default to 7.
- In situ primary with positive nodes or metastases: code 3 or 7. The behavior becomes /3, because an invasive component must exist.
- Unknown node status is treated as "none." If there is no information on distant metastasis, assume there is none.
- Regional Nodes Positive coded 01–90, 95 or 97 means nodes are involved, so Summary Stage must be 3, 4 or 7.
- Multiple tumors abstracted as one primary: assign the greatest stage from any tumor.
- Neoadjuvant therapy: use surgical findings after neoadjuvant treatment only if the extent is greater than the pre-treatment clinical findings. Otherwise use the clinical findings.
- Autopsy reports are used like pathology reports.
- TNM only: T, N and M information may be used when it is the only information. If TNM and the medical record disagree, use the record, and query the physician if possible.
- Chapter-specific instructions override the general instructions.
Code 9 rules
- Unknown primary (C809) must be coded 9.
- Death certificate only cases are always 9, even for histologies with a default stage. The manual's example: AML known only from a death certificate is 9, not 7.
- Use 9 sparingly. Typical reasons are death before workup, refusal of diagnostic procedures, a limited workup, or a biopsy that alone cannot show extent.
Code 8 rules
- Code 8 is only for benign or borderline tumors in the brain and CNS chapters, such as meningioma 9530/0 or vestibular schwannoma 9560/0.
- If a registry collects other non-reportable benign or borderline tumors, Summary Stage is 9, not 8.
High-yield chapters
Cutaneous melanoma
| Code | Examples |
|---|---|
| 0 | Melanoma in situ |
| 1 | Confined to the dermis, or through the dermis into subcutaneous tissue |
| 2 | Direct extension into bone, cartilage, fascia or skeletal muscle |
| 3 | Regional lymph nodes, including isolated tumor cells, and in-transit, satellite or microsatellite metastases, with or without regional nodes (they are counted as positive nodes) |
| 4 | Codes 2 + 3 |
| 7 | Distant sites or distant nodes |
Breslow thickness and ulceration change the AJCC T category but not Summary Stage. For example, a 6.0 mm ulcerated melanoma with no spread is 1.
Lymphoma
Codes 0, 3 and 4 are not used.
| Code | Nodal lymphomas | Extranodal lymphomas |
|---|---|---|
| 1 | A single lymph node region, including several chains in the same region | A single extralymphatic site without nodes |
| 2 | Two or more node regions on the same side of the diaphragm | A single extralymphatic site with its regional nodes, or other nodes on the same side of the diaphragm |
| 7 | Node regions on both sides of the diaphragm; nodes above the diaphragm plus spleen | Diffuse or disseminated organ involvement; bone marrow, peripheral blood, CSF, liver, or lung (other than direct extension); bilateral paired organs (for example, both eyes) |
Lymph node descriptions such as "enlarged," "shotty," "matted" or "lymphadenopathy" count as involvement for lymphoma.
Myeloma and other heme neoplasms
- Plasma cell myeloma (9732) is always 7. So are lymphoplasmacytic lymphoma (9671) and Waldenström macroglobulinemia (9761).
- A single plasmacytoma of bone (9731) or outside bone (9734) is 1. An extraosseous plasmacytoma with regional nodes is 3.
- Leukemias and most myeloid neoplasms are 7, using the "Hemeretic" chapter. A few histologies, such as myeloid sarcoma and histiocytic sarcoma, can be 1, 7 or 9.
Crosswalk examples
| Case | Summary Stage |
|---|---|
| DCIS with microinvasion of 1 mm, nodes negative | 1 |
| Colon adenocarcinoma into the submucosa, 0/14 nodes | 1 |
| Colon adenocarcinoma invading subserosal fat, 0/16 nodes (AJCC pT3) | 1: the colon chapter lists subserosal tissue under localized |
| Sigmoid adenocarcinoma invading "pericolonic tissue," 0/16 nodes | 2: the sigmoid is entirely peritonealized, so pericolonic tissue invasion there is regional |
| Breast 1.8 cm, 2 of 12 axillary nodes positive | 3 |
| Lung primary with a biopsy-proven brain metastasis | 7 |
| Acute myeloid leukemia on bone marrow biopsy | 7 |
| AML known only from a death certificate | 9 |
| Benign meningioma | 8 |
A cutaneous melanoma of the thigh has two satellite nodules within 2 cm of the primary. Sentinel lymph node biopsy is negative, and there are no distant metastases. How is Summary Stage 2018 coded?
1, because satellite nodules are part of the primary tumor
2, because satellite nodules are regional direct extension
3, because in-transit, satellite and microsatellite metastases are counted as positive regional nodes
7, because the nodules are discontinuous from the primary
A rectal cancer is clinically confined to the rectal wall (no extension, nodes negative) before neoadjuvant chemoradiation. After treatment, the resection shows only residual tumor in the muscularis propria, with 0 of 15 nodes positive. How is Summary Stage assigned?
1, from the pre-treatment findings, because post-treatment surgical findings are used only when they show greater extent
9, because treatment makes the extent unknown
0, because only a small amount of tumor remains
2, because neoadjuvant therapy always implies regional disease
Diffuse large B-cell lymphoma involves cervical and axillary lymph nodes (both above the diaphragm), and the bone marrow biopsy is positive. How is Summary Stage coded?
1, because only lymph nodes are involved
2, because two node regions on the same side of the diaphragm are involved
3, because lymph nodes are involved
7, because bone marrow involvement is distant in the SS2018 lymphoma chapter
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