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Code adenocarcinoma in situ as 8140/2 using the 2018 Lung Solid Tumor Rules, Rule H4 as this single histology is listed as a synonym for adenocarcinoma (8140) in Table 3 . Bronchiolalveolar carcinoma, a synonym for adenocarcinoma in situ, is an obsolete term according to WHO Classification of Tumors of the Lung, Pleura, Thymus and Heart, 4th edition; however, some pathologists add in the no longer preferred term to the diagnosis. When stated as non-mucinous adenocarcinoma in situ, code as 8250/2 for lung only (Rule H2) and mucinous adenocarcinoma in situ as 8253/2 (Rule H1).

Note: WHO published a corrected 4th Ed Lung blue book fixing the 8410 error.

Assign 8249/3 for high-grade neuroendocrine tumor of the lung.

WHO Classification of Thoracic Tumors, 5th edition, defines two subtypes of neuroendocrine tumor of the lung, typical carcinoids (8240/3), and atypical carcinoids. WHO assigns typical carcinoid/neuroendocrine tumor grade 1 as 8240/3 and atypical carcinoid/neuroendocrine tumor grade 2 as 8249/3. They are regarded as low-grade and intermediate-grade, respectively. The preferred term for 8249/3 in ICD-O-3.2 is neuroendocrine tumor grade 2, with neuroendocrine tumor grade 3 as a related term. The Lung Solid Tumor Rules assign atypical carcinoid as 8249/3.

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. 

Assign histology as squamous cell carcinoma, HPV positive (8085) for tonsil, NOS (C099) based on the positive HPV test. Codes 8085 and 8086 are valid for a select group of sites. The histology terms and codes that are valid for head and neck sites are included in the Head and Neck Solid Tumor Rules, Table 5 (oropharynx).

HPV detection tests that are used to identify HPV include DNA polymerase chain reaction (PCR), p16 (IHC), or DNA/RNA in situ hybridization. Assign the appropriate method of detection in the SEER data item, SEER Site-Specific Factor 1.  

Schema Discriminator 2 captures additional information needed to generate AJCC ID and Schema ID for some anatomic sites as stated in the SSDI Manual. For oropharyngeal cancer, a schema discriminator is used to discriminate between oropharyngeal tumors that are p16 positive, p16 negative, or p16 status unknown in order to assign the appropriate schema ID. Only the HPV p16 test can be used to assign Schema Discriminator 2. If another HPV test is performed, code 9. Override the edit for Schema Discriminator 2 when p16 is negative. Coding updates will be implemented in 2025.

Sites may be added to certain combinations when indicated by ClinCORE review for Cancer PathCHART. Please note some sites were added in the 2024 update as a result of PathCHART review. A newly-formed Solid Tumor Editorial Board and its subgroups are currently working to evaluate the Solid Tumor Manual and make recommendations on ways to improve the structure and formatting of the manual and its content.

Follow the rules and instructions in the Other Sites STRs when assigning combination histology codes.

Histology Coding Rules

Use the Histology Coding Rules when assigning combination codes.

Coding Histology Information

Use this section that includes the mixed histology (Table 2) and site-specific histology tables (Tables 3-23) for one or more histologies within a single tumor. Do not use this section in place of the Histology Coding Rules.

While site-specific histology tables, based on current WHO Classification of Tumors books, have been added to Other Sites STRs, not all site groups have individual histology tables; coding may require the use of ICD-O and updates. The histology tables in Other Sites STRs include additional coding instructions and notes to assign the correct ICD-O code when appropriate.

The tables are not meant to be all-inclusive; rather they are intended to address difficult coding situations to facilitate the assignment of the correct histology code.

Table 2: Mixed and Combination Codes Instructions

Once you have identified the histology terms and have been instructed to use Table 2 by the Histology Coding Rules, compare the terms in the diagnosis to the terms in Column 1. When the terms match, use the combination code listed in Column 2. Use adenocarcinoma mixed subtypes 8255 as a “last resort” code.

The rule order is the same as in the previous MP/H rules. Will keep as is for now.

Assign codes adenocarcinoma in adenomatous polyp (8210), adenocarcinoma in villous adenoma (8261), and (adenocarcinoma in tubulovillous adenocarcinoma (8263) using Other Sites Solid Tumor Rule H12 or Rule H27 as these are specific invasive histology codes. Rule H13 applies to histology codes associated with polyps but associated with a histology term/code other than adenocarcinoma.

Abstract this case as a single primary. Code as 8044/3 (small cell carcinoma, hypercalcemic type) listed in the Other Sites Solid Tumor Rules, Table 13. Small cell carcinoma, large cell variant, is a subtype of small cell carcinoma, hypercalcemic type. This table does not include all possible histologies.

WHO Classification of Female Genital Tumors, 5th edition, states: Small cell carcinoma of the ovary, hypercalcemic type, is rare, accounting for < 1% of ovarian tumors. Small cell carcinomas, hypercalcemic type, are usually large, with a mean size of 15 cm (range: 6–26 cm). Large cells are present (in varying numbers) in half of these tumors, which are designated “small cell carcinoma, large cell subtype” if the large cells are predominant (which is rare).

Assign code 8461/3 for high-grade papillary serous carcinoma.

Code myoepithelial carcinoma ex pleomorphic adenoma as carcinoma ex pleomorphic adenoma (CXPA) (8941/3) using Head and Neck Solid Tumor Rule H1 as this is a single histology.  The WHO Classification of Head and Neck Tumors, 5th ed., describes CXPA as a rare epithelial and/or myoepithelial malignance arising in association with a primary or recurrent pleomorphic adenoma.  The histologic type of the carcinoma component is usually recorded, in this case, myoepithelial carcinoma.

Assign histology code 8054/3 for warty carcinoma. Assign 8051/3 for verrucous carcinoma and carcinoma cuniulatum. 

The WHO Classification of Urinary and Male Genital Tumors, 5th edition (2022) revised the terminology for squamous cell carcinoma groupings from "non-HPV-related" to "HPV-independent" and from "HPV-related to "HPV-associated". Warty carcinoma is defined as a "morphologically distinct HPV-associated verruciform neoplasm that shares histological features with a giant condyloma but has definitive cytological atypia and a malignant infiltrative architecture."  Verrucous carcinoma (including carcinoma cuniculatum) is defined as an HPV-independent squamous cell carcinoma, and is correctly coded to 8051/3.

The 2024 Solid Tumor Rules, Table 23, Penis and Scrotum Histologies will be updated to reflect this revised terminology and coding.