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.

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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)