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Table 3 (Breast Equivalent Terms and Definitions) lists “Neuroendocrine tumor, well-differentiated” of the breast as histology 8246/3. There is no entry for a grade 2 neuroendocrine tumor of the breast in Table 3.  

The pathologist did not indicate the neuroendocrine tumor was poorly differentiated (or it would otherwise be a small cell carcinoma). The pathologist noted “By current WHO criteria, this tumor is characteristic of a mammary neuroendocrine tumor, grade 2.  These invasive tumors have similar prognostic and predictive features of invasive ductal carcinoma of the same grade and stage.”

Patient was diagnosed on 01/2020, and primary site on the pathology report is Ampulla of Vater (C241). Synoptic Report states histology as: Intra ampullary papillary-tubular neoplasm in association with microinvasion.

I have reviewed the ICD-O-3 coding table and found histology Intraductal tubulopapillary neoplasm (C25_) code 8503/2. Based on the Matrix principle (Rule F on the ICD-O-3), I will change the behavior to 3 and code as 8503/3. If I look in ICDO-3, Tubulopapillary adenocarcinoma is coded 8263/3.

Histologic Type: HPV-associated multiphenotypic carcinoma. Overall, the morphology, immunohistochemistry, and HPV testing results support the diagnosis of an HPV-related multiphenotypic carcinoma. This entity has been described in the sinonasal region, where it behaves more indolently than its other salivary gland carcinoma counterparts (e.g., adenoid cystic carcinoma), with local recurrence but rare metastases.

The Schema ID for C051 (soft palate, NOS) and C052 (uvula) is Oropharynx (either 00100 or 00111 depending on p16). The Solid Tumor Rules Manual includes these site codes are under Table 4: Tumors of Oral Cavity and Mobile Tongue site group for histology coding. We are aware of the notes that allow coding of 8086 for keratinizing SCC, HPV-negative for sites listed in Table 5 only. However, it seems like C051 and C052 were incorrectly omitted from Table 5 (mis-categorized under Table 4). Can we code 8085 for 8086 for C051 or C052 based on p16/HPV status?

Per Mayo consulting pathologist, the final diagnosis on this right lung biopsy is: SMARCA4-deficient malignant neoplasm (see Comment). Comment: Sections show a poorly-differentiated malignant neoplasm without any apparent glandular, squamous, or stromal differentiation. The tumor near totally replaces the underlying lung tissue without recognizable underlying alveolar parenchyma. Immunohistochemical stains performed at Mayo Clinic (Oscar keratin, INSM1, NUT, S100, desmin and BRG1 protein encoded by SMARCA4 gene) demonstrate that the malignant cells are positive for Oscar keratin (rare cells only), synaptophysin (weak/patchy) and p63 (focal) while negative for the remaining antibodies tested. Of note, SMARCA4 stain is negative in the tumor cells. Thus, this tumor can be categorized as a SMARCA4-deficient malignant neoplasm, which is known to be an aggressive malignancy, likely represent a SMARCA4-deficient thoracic sarcoma, a recently described entity. SMARCA4-deficient carcinomas in the lung have been reported to be mostly adenocarcinomas or squamous cell carcinomas, which would not fit for this case. Please refer to a paper published by our group (Sauter JL et al. Mod Pathol 2017;30:1422-32.

The term “poorly differentiated carcinoma (NOS)” is listed as related to “undifferentiated carcinoma (NOS)” in the ICD-O 3.2. It is also listed in the Solid Tumor Rules for Urinary Table 2 (Urinary subtypes), Other Sites Table 16 (uterine corpus primaries) and Table 19 (vulvar primaries).

Are these the only sites in which one should code “poorly differentiated carcinoma (NOS)” as 8020 (undifferentiated carcinoma)?

How is histology coded if the only microscopic confirmation is from a metastatic site showing “poorly differentiated carcinoma” (NOS) or “invasive carcinoma, poorly differentiated” (NOS)?

Example 1: Primary pancreatic cancer diagnosed on imaging and confirmed with liver mets core biopsy showing “poorly differentiated carcinoma.” Immunostaining pattern was non-specific. No further workup or treatment was planned.

Other Sites - Table 11 (Pancreas Histologies) includes undifferentiated carcinoma (8020/3) as a valid histology; however, the synonyms/subtypes/variants do not mention poorly differentiated carcinoma. How should histology be coded for this case?

Example 2: Hemicolectomy with cecal tumor final diagnosis of “invasive carcinoma, poorly differentiated” and synoptic summary listing “Histologic type: Invasive carcinoma. Histologic grade: G3 of 4: poorly differentiated.”

Colorectal Table 1 (Specific Histologies and Subtypes/Variants) includes undifferentiated adenocarcinoma/carcinoma 8020 as a subtype of adenocarcinoma NOS. There is no mention of poorly differentiated in this context. How should histology be coded for this case?

The pathology report states this is a rare entity described in case reports and not incorporated into the WHO classification of tumors. A subsequent endocrinology note stated “papillary tumor, benign by path; tumor was not an adenoma; based on one Mayo study, the recurrence risk is low.”

Example: Breast case where first course treatment plan is neoadjuvant therapy and surgery after. The patient was hospitalized during neoadjuvant therapy, elected hospice, and later died, so the neoadjuvant therapy was never completed, surgery not done. How are the 2021 neoadjuvant therapy fields coded in this situation as neoadjuvant therapy and surgery were part of first course plans. I coded neoadjuvant therapy to 2 - started but not completed, but there are no codes to properly explain the clinical response and therapy treatment effect as the patient did not complete neoadjuvant therapy. Should I use code 9 for clinical response and treatment effect or should this be left blank for this particular case?