The following changes were included in the Solid Tumor Rules 2026.1 Update. This is a document containing changes only. Do not use in place of the Solid Tumor Rules.

See the December 2025 Revisions
See the November 2024 Revisions
See the December 2023 Revisions
See the May 2023 Revisions
See the December 2022 Revisions
See the September 2021 Revisions
See the December 2020 Revisions
See the November 2020 Revisions
See the July 2019 Revisions
See the April 2019 Revisions
See the 2018 Revisions

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Changes Across All Site-groups

Site-group Instructions

  • Updated histology tables as necessary to align with Cancer PathCHART (CPC) standards
    • Includes adding/removing histologies, updating terms, and adding behavior codes

Histology Rules

  • Coding Histology section:
    • Updated Note 1 (except Breast Site-group) (no change in meaning)
    • Simplified the "differentiation and features" instruction (no change in meaning)
    • Moved Definitive terms notes below table header (no changes to text)
    • Ambiguous Terminology instructions (no change in meaning)
      • Added conjunctions for clarity
      • Removed redundant bullets
  • Added bullet to note for the "different rows" rule:
    • "Histologies can be in any column; however, the histologies must be on different rows" (no change in meaning)
  • Simplified wording in the "same row" rule (no change in meaning)

General Instructions

  • "Diagnosis Years for Which the Solid Tumor Rules Should be Used" section:
    • Paraganglioma histology list corrected in footnote (*)
  • "How to Use the Multiple Primary Rules" section:
    • Re-added statement to #3b that had been inadvertently deleted: "When there is a tumor or tumors with separate microscopic foci, ignore the microscopic foci. If a measurement is provided for the focus, then use the Multiple Tumors Module."
    • Added text to #3c: "When proceeding to the Histology Rules, use the appropriate Single Tumor Module."
  • "How to Use the Histology Rules" section:
    • #1a: Added Note 2 (clarification)

Breast

Site-group Instructions

  • Introduction: Removed Note 6 regarding CAP Protocol (note was not valuable)
  • Table 2: Histology Combination Codes: removed Bullet 1 of Note 1 (was inaccurate)
  • Table 3: Specific Histologies, NOS/NST, and Subtypes/Variants:
    • Apocrine carcinoma 8401 row:
      • Added "(/3)"
    • Carcinoma NOS 8500 row:
      • Added synonym "Apocrine carcinoma in situ" for 8500/2
      • Removed "Pleomorphic carcinoma 8022 (/3)" from column 2
    • Removed "Medullary carcinoma" row and its subtype
    • Sarcoma NOS 8800 row:
      • Removed subtype/variants:
        • Lymphangiosarcoma 9170 (/3)
        • Malignant hemangioendothelioma 9130 (/3)

Histology Rules

  • "Coding Histology" section:
    • "This instruction applies to single and multiple histologies" added to Note preceding Coding Histology section (no change in meaning)

Colon

Site-group Instructions

  • Introduction: Removed unnecessary Note 5 and renumbered remaining notes
  • Table 1: Specific Histologies, NOS, and Subtypes/Variants
    • Adenocarcinoma 8140 row:
      • Removed "Adenoid cystic carcinoma 8200" from column 2
      • Removed "Diffuse adenocarcinoma 8145" from column 2
      • Added "(/3)" to Medullary adenocarcinoma
    • Gastrointestinal stromal tumor 8936 row:
      • Synonyms added:
        • "GIST, behavior not stated (2021+)"
        • "GIST, benign (2021+)"
        • "GIST, borderline (2021+)"
      • "2021+" added to GIST NOS
    • NEC and NET rows: "(/3)" added to all codes
    • Neuroendocrine tumor Grade 1 8240 row:
      • Removed "Somatostatin-producing neuroendocrine tumor Grade 2 8156" from column 2
  • Table 2: Histologies Not Reportable for Colon, Rectosigmoid and Rectum
    • Row deleted: Gangliocytic paraganglioma 8683 (/0)
    • Gastrointestinal stromal tumor 8936 (/1) row:
      • Reportability notes added
      • Synonyms added:
        • "GIST, benign"
        • "GIST, borderline"
  • Table 3: Primary Site Codes
    • Removed "Left colon" from C188 row (this was an error)

Head and Neck

Site-group Instructions

  • Table 1: Tumors of Nasal Cavity, Paranasal Sinuses and Skull base
    • Sarcoma 8800 NOS row:
      • Subtypes/variants removed:
        • "Malignant hemangioendothelioma 9130 (/3)"
        • "Undifferentiated pleomorphic sarcoma 8802 (/3)"
    • Squamous cell carcinoma 8070 row:
      • Subtype/variant removed:
        • "Schneiderian carcinoma 8121"
  • Table 2: Tumors of Nasopharynx
    • "Low-grade nasopharyngeal papillary adenocarcinoma 8260" row:
      • "Low-grade" added to preferred term; removed from alternate term
  • Table 3: Tumors of Pyriform Sinus, Hypopharynx, Larynx, Trachea, and Parapharyngeal Space
    • Squamous cell carcinoma 8070 row:
      • Footnote 4 removed
  • Table 4: Tumors of Oral Cavity and Mobile Tongue
    • Squamous cell carcinoma 8070 row:
      • Deleted synonym: "High-grade intraepithelial squamous lesions (/2)" (was included in error)
      • Added footnote to Non-keratinizing squamous cell carcinoma 8072
  • Table 5: Tumors of the Oropharynx, Base of Tongue, Tonsils, Adenoids
    • Table notes clarified: Both keratinizing and non-keratinizing are included in the exception (clarification)
    • Squamous cell carcinoma 8070 row:
      • Added to footnote 2: "2026+: 8072/3 should only be used for C111 (Posterior wall of nasopharynx)."
      • Other footnotes simplified and consolidated (no change in meaning)
      • Squamous cell carcinoma HPV-negative 8086:
        • Synonym added: "Keratinizing squamous cell carcinoma, HPV-negative"
      • Squamous cell carcinoma HPV-positive 8085:
        • Synonym added: "Non-keratinizing squamous cell carcinoma, HPV-positive"
  • Table 6: Tumors of Salivary Glands
    • Neuroendocrine carcinoma 8246 row: "(/3)" added to all histologies
  • Table 9: Paraganglioma of Carotid Body, Extra-adrenal, Larynx, Middle Ear, Vagal Nerve
    • Paraganglioma reportability note for "Cases diagnosed 1/1/2021 forward" simplified and corrected
      • "unless otherwise stated by the pathologist" removed (was inaccurate). This is a coding change.
    • Footnote updated to add: “All paragangliomas are reportable as malignant.”

Kidney

Site-group Instructions

  • Table 1: Specific Histologies, NOS, and Subtypes/Variants:
    • Sarcoma 8800 row:
      • "Alveolar rhabdomyosarcoma 8920 (/3)" added back to Sarcoma row (was removed in error)
    • Renal cell carcinoma NOS 8312 row:
      • Added line break between "Fumarate hydratase deficient RCC" and "ALK rearranged RCC" (8311)
  • Table 2: Neoplasms which are Not Reportable:
    • Code for paraganglioma corrected to 8693

Lung

Site-group Instructions

  • Table 2: Combination/Mixed Histology Codes
    • Adenocarcinoma with mixed subtypes 8255 (/3) row:
      • "patterns" added to bullets in column 1 (this is a clarification, not a change)
  • Table 3: Specific Histologies, NOS, and Subtype/Variants
    • Diffuse pulmonary lymphangiomatosis 9170 row:
      • "(/3)" added
    • Row deleted: "Intrapulmonary thymoma (arising within lung) 8580 (/3)"
    • Sarcoma 8800 row:
      • Subtype/variant deleted: "Pulmonary artery intimal sarcoma 9137 (/3)"
    • Large cell carcinoma 8012 row:
      • Footnote updated: "highly differentiated" changed to "undifferentiated non-small cell carcinoma" (this is a correction to terminology)

Histology Rules

  • H Rules: Code the subtype/variant when there is an NOS and a single subtype/variant …
    • Bullet deleted: "Mucinous adenocarcinoma and a subtype/variant of mucinous adenocarcinoma" (there are no subtypes; rule does not apply)
  • H Rules in both modules: Code the histology when only one histology is present in all tumors.
    • Notes regarding 8010/2 being impossible in CPC deleted (was inaccurate). This is a coding change.

Malignant CNS

Site-group Instructions

  • Introduction:
    • Notes regarding pilocytic astrocytoma, optic glioma, and HGAP simplified and consolidated into new Notes 6 and 7 (no change in meaning)
    • Removed inaccurate notes regarding paragangliomas
  • Behavior Code section:
    • Instruction #6, Example 2: Behavior code for meningioma corrected from /1 to /0 (no change in meaning)
  • WHO Grades for Select CNS Neoplasms section:
    • Note 2: "SEER and CoC Manuals" updated to "Grade Manual" (correction)
  • Table 2: Specific Histologies, NOS, and Subtypes/Variants
    • Sarcoma 8800 row:
      • Code for Sarcoma with BCOR genetic alterations corrected to "9368"
    • Astrocytoma NOS 9400 row:
      • Clarified that "Astrocytoma, IDH-mutant, grade 3" is a synonym of 9401
    • Oligodendroglioma NOS 9450 row:
      • Duplicate synonym deleted for 9451

Non-Malignant CNS

Site-group Instructions

  • Introduction:
    • Notes regarding pilocytic astrocytoma and optic glioma simplified and consolidated into new Note 4 (no change in meaning)
    • Removed inaccurate note regarding paragangliomas
  • Behavior Code section:
    • Instruction #6, Example 2: Behavior code for meningioma corrected from /1 to /0 (no change in meaning)
  • WHO Grades for Select CNS Neoplasms section:
    • Note 2: "SEER and CoC Manuals" updated to "Grade Manual" (correction)
  • Table 5: Specific Histologies, NOS, and Subtypes/Variants
    • Rows removed:
      • "Chondroma 9220 (/0)"
      • "Rhabdomyoma 8900 (/0)"
    • Hemangioma 9120 (/0) row:
      • Moved the synonym "Cavernoma" from 9120 to 9121 (This is a coding change)
    • Paraganglioma 8693 (/1) row:
      • Clarified footnote regarding paraganglioma reportability (This is a coding change)
  • Table 7: Non-Malignant CNS Tumors with the Potential of Transforming to Malignant Behavior
    • Rows removed:
      • "Chondroma 9220 (/0)"
      • "Rhabdomyoma 8900 (/0)"

Multiple Primary Rules

  • M Rule: Abstract a single primary when separate/non-contiguous tumors are on the same row…
    • Exceptions clarified and moved to Note bullet 1 (no change in meaning)

Histology Rules

  • H Rule: Code the subtype/variant when there is an NOS and a single subtype/variant…
    • Behavior code for Solitary fibrous tumor WHO Grade 1 updated to "/1" (correction)

Other Sites

Site-group Instructions

  • Terms That Are NOT Equivalent or Equal
    • "melanoma" added to note (clarification)
  • Table 2: Mixed and Combination Codes
    • Adenocarcinoma with mixed subtypes 8255 row:
      • Removed inaccurate footnote that stated: "Code 8255 does not apply to GYN primaries. Continue through the table to determine correct mixed histology code for GYN neoplasms." This is a coding change.
    • Combined large cell neuroendocrine carcinoma 8013 row:
      • Added "(/3)"
    • Combined small cell carcinoma 8045 row:
      • Added "(/3)"
  • Table 3: Prostate Histologies
    • Coding notes clarified: "Ductal adenocarcinoma or ductal carcinoma with no other histologies present (% ductal not needed)" can be coded 8500. This is a coding change.
    • Acinar adenocarcinoma 8140 row:
      • Added "(/2)" to Intraductal adenocarcinoma
    • Row deleted:
      • Urothelial carcinoma 8120
  • Table 5: Esophagus Histologies
    • Gastrointestinal stromal tumor 8936 (/3) row:
      • Footnote clarifying reportability added
      • Synonyms added:
        • GIST, behavior not stated (2021+)
        • GIST, benign (2021+)
        • GIST, borderline (2021+)
      • "2021+" added to GIST NOS
  • Table 6: Stomach Histologies
    • Gastrointestinal stromal tumor 8936 (/3) row:
      • Footnote clarifying reportability added
      • Synonyms added:
        • GIST, behavior not stated (2021+)
        • GIST, benign (2021+)
        • GIST, borderline (2021+)
      • "2021+" added to GIST NOS
  • Table 7: Small Intestine and Ampulla of Vater Histologies
    • Gastrointestinal stromal tumor 8936 (/3) row:
      • Footnote clarifying reportability added
      • Synonyms added:
        • GIST, behavior not stated (2021+)
        • GIST, benign (2021+)
        • GIST, borderline (2021+)
      • "2021+" added to GIST NOS
  • Table 11: Pancreas Histologies
    • Glandular intraepithelial neoplasia, high grade 8148 (/2) row:
      • "high grade" added to all synonyms
    • Neuroendocrine carcinoma NOS 8246 row:
      • "(/3)" added to all histologies
    • Neuroendocrine tumor NOS 8240 row:
      • "(/3)" added to all histologies
  • Table 14: Peritoneum Histologies
    • Gastrointestinal stromal tumor 8936 (/3) row:
      • Footnote clarifying reportability added
      • Synonyms added:
        • GIST, behavior not stated (2021+)
        • GIST, benign (2021+)
        • GIST, borderline (2021+)
      • "2021+" added to GIST NOS

Multiple Primary Rules

  • M Rule: Abstract a single primary when follicular and papillary tumors in the thyroid…
    • Clarified wording (no change in meaning)
  • M Rule: Abstract a single primary when synchronous, separate/non-contiguous tumors are on the same row…
    • Moved note 2 to under bullet 1 as an exception.
    • Added "See exception" (no change in meaning)
  • M Rule: Abstract multiple primaries when separate/non-contiguous tumors are on different rows…
    • Added note (no change in meaning)

Histology Rules

  • Coding Histology section:
    • "melanoma" added to Instruction #1, Note 2 (clarification)
  • H Rule: Code the histology documented by the physician when the pathology/cytology report is not available.
    • Removed 8000/2 from Note 3 (correction)
  • H Rule (both modules): Code 8140 (adenocarcinoma NOS) for prostate primaries when the diagnosis is…
    • "mixed with acinar adenocarcinoma NOS" added to the ductal adenocarcinoma bullet (This is a coding change)
    • Redundant information removed from note

Urinary

Site-group Instructions

  • Table 1: ICD-O Primary Site Codes:
    • Note added
    • Bladder neck C675 row:
      • "Internal ureteral orifice" added to column 2
    • Bladder NOS C679 row:
      • "Posterolateral wall" added to column 2
      • Footnote added
    • Bladder, overlapping lesion C678 row:
      • Footnote added
    • Bladder, trigone C670 row:
      • "Below interureteric field" corrected to "Below interureteric fold"
    • Urethra C680 row:
      • "Penile urethra" and "Prostatic urethra" added to column 2
  • Table 2: Specific Histologies, NOS, and Subtypes/Variants
    • Adenocarcinoma NOS 8140 row:
      • "Signet ring cell adenocarcinoma 8490 (/3)" added to column 2
      • Added "(/3)" to 8310 and 8380
    • Mixed neuroendocrine-non-neuroendocrine neoplasm 8154 (/3) row:
      • Changed "carcinoma" to "neoplasm" and added "MiNEN" as a synonym
    • Neuroendocrine carcinoma NOS 8246 (/3) row:
      • "Large cell neuroendocrine tumor 8013 (/3)" corrected to "Large cell neuroendocrine carcinoma 8013 (/3)"
    • Neuroendocrine tumor NOS 8240 (/3) row:
      • "Well-differentiated neuroendocrine tumor" added as a synonym
    • Sarcoma NOS 8800 (/3) row:
      • Subtypes/variants added:
        • "Alveolar rhabdomyosarcoma 8920 (/3)"
        • "Spindle cell rhabdomyosarcoma 8912 (/3)" and synonym "Sclerosing rhabdomyosarcoma (/3)"
    • Urothelial carcinoma 8120 row:
      • Synonym added: "Transitional cell carcinoma (obsolete)"
      • Synonym deleted: "Urothelial carcinoma in situ" (unnecessary)
      • "transitional cell" removed from the term "Papillary urothelial carcinoma 8130" in column 2
      • "invasive (/3)" and "in situ (/2)" removed as synonyms of Papillary urothelial carcinoma 8130
      • Footnote regarding transitional cell carcinoma deleted
  • Table 3: Non-Reportable Urinary Tumors
    • Paraganglioma 8693 (/1): Note added (no change in meaning)

Multiple Primary Rules

  • M Rule: Abstract a single primary when there are urothelial carcinomas in multiple urinary organs:
    • "melanomas" added to Note 1 (clarification)
  • M Rule: Abstract multiple primaries when the ICD-O site code differs at the second (CXxx) and/or third (CxXx) character.
    • Note and examples added (no change in meaning)

Histology Rules

  • Coding Histology section:
    • "melanoma" added to Instruction #1, Note 1 (clarification)
  • H Rules: Code mixed small cell carcinoma…
    • "melanoma" added to rule statement (clarification)
  • H Rules: Code combined large cell…
    • "Combined large cell carcinoma" corrected to "combined large cell neuroendocrine carcinoma"
    • "melanoma" added to main rule statement (clarification)