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Abstract a single primary using Solid Tumor Rules, Malignant CNS and Peripheral Nerves, Rule M10 based on the information provided.  Rule M10 applies as both non-contiguous tumors are of the same histology; i.e., on the same row in Table 3. As MPNST can arise in many sites, look for information about the precise location and tissue type in which the tumor arose. For example, if the tumors are stated to arise in soft tissue, follow the Multiple Primary Rules for Other Sites.

Both WHO Classification of Central Nervous System Tumors and WHO Classification of Soft Tissue and Bone Tumors state that MPNST is a malignant spindle cell tumor often arising from a peripheral nerve, from a pre-existing benign nerve sheath tumor, or in a patient with neurofibromatosis type 1 (NF1).

Future updates will move C470-C479 from CNS to other sites module.

The Solid Tumor Rules for Lung have been updated for 2024. The row for Small cell carcinoma 8041/3 has been deleted and new separate rows have been added for Neuroendocrine carcinoma (NEC) 8246 and Neuroendocrine tumor, NOS (NET) 8240. This change is based on the WHO Classification of Thoracic Tumors, 5th edition, and current concepts. In addition, Table 3 now reflects that Small cell carcinoma/small cell neuroendocrine carcinoma 8041 (located in Column 3) is a subtype/variant of neuroendocrine carcinoma, NEC 8246 (Column 1). As a result, application of Rule H6 to a diagnosis of poorly differentiated neuroendocrine carcinoma (small cell carcinoma)” would be coded as 8041, instead of 8246. Please note: the 2024 updates may be used for cases diagnosed prior to 1/1/2024 unless otherwise noted in the rules.

Code to poorly differentiated thyroid carcinoma, 8337/3.

In this case the tumor is comrpised of two difffernat thyroid histologies: poorly differentiated carcinoma 8337/3 and papillary thyroid carcinoma 8260/3. WHO does not have a code for this combination. Per our endocrine pathology expert, the poorly differentiated carcinoma is the more agressive histology and will determine treatment and progrnosis.

High grade squamous dysplasia of the tongue is reportable as of 2021 and later as 8077/2.

Assign code 8742/2 (lentigo maligna) for “early lentiginous melanoma in situ.” ICD-O-3.2 lists the preferred term for 8742/2 as lentigo maligna (C44._).

Assign histology code 8254/3 (mixed invasive mucinous and non-mucinous adenocarcinoma) to this lung tumor using Lung Solid Tumor Rules, Rule H4. This is a new code/term approved by IARC/WHO for ICD-O. Rule H4 instructs one to code the histology when only one histology is present. In this case, the pathologist indicates the tumor is mixed mucinous and non-mucinous histologies. The non-mucinous carcinoma that is seen in this mixed histology may be identified as: Adenocarcinoma in situ, minimally invasive adenocarcinoma, or lepidic predominant adenocarcinoma. In this case it is lepidic predominant adenocarcinoma. Lepidic is a recognized histology in lung. It is not unusual for the pathologist to indicate mixed non-muncinous and mucinous adenocarcinoma AND also list the non-mucinous subytpe. It is important to capture both mucinous and non-mucinous histologies which drives treatment, etc. 

For cases diagnosed in 2023 and later, Update to the current manual: Assign code 13 (Radioisotopes, NOS) in Radiation Treatment Modality--Phase I, II, III for PRRT.

We will make this change in the next version of the SEER Manual.

This case does not fall into the standard rules. WHO criteria for diagnosing pituitary adenoma have recently changed (per 5th Ed WHO CNS book) and we will likely see more PitNET’ s than pituitary adenomas in the future.  PitNET may be invasive or non-invasive but the likelihood of the pathologists providing this information is low. Since we don’t know if the 2018 adenoma was a PitNET based on current criteria or if it transformed to the malignant neoplasm, err on the side of caution and abstract a second primary per M5.

This issue is new, and we’ve received numerous questions concerning pathologist reviewing older cases of pituitary adenoma and reclassifying them as PitNET using the new criteria.

For the example provided: For 2023 cases and forward, if no part of the surgery was performed, code Surgery of Primary Site 2023 (NAACCR Item #1291) as code A000 or B000 (no surgical procedure of the primary site).  Code Reason for No Surgery of Primary Site (NAACCR Item #1340) as code 2 (surgery of the primary site was not recommended/performed because it was contraindicated due to patient risk factors (comorbid conditions, advanced age, progression of tumor prior to planned surgery, etc.).

In contrast, if any part of the surgery was performed, assign the Surgery of Primary Site 2023 (NAACCR Item #1291) code that best reflects the extent of the surgery performed.  Code Reason for No Surgery of Primary Site (NAACCR Item #1340) as code 0 (surgery of the primary site was performed).

Use text fields to record the details.

For cases prior to 2023, apply the same approach using Surgery of Primary Site (NAACCR Item #1290) instead of Surgery of Primary Site 2023 (NAACCR Item #1291).

Assign 8140/3 (adenocarcinoma, NOS). WHO has not yet recognized the variant amphicrine prostate carcinoma and have not proposed an ICD-O code for this neoplasm. Document information in a related text field.