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After consultation with our expert pathologist, the decision is report this case as a single primary. There was some confusion about how to apply the current MP/H rules to this pathology report given 1) the definition of M16 and M17 and 2) the likelihood for a single endometrial primary to present with several differentiations. According to our expert pathologist, "I would regard this case as a single endometrial primary with extensive endometrial involvement and several types of differentiation, all of which are seen in endometrial carcinomas."

Next, the Multiple Primary and Histology Coding Rules Manual is the correct source for coding histology for cases diagnosed 2007 or later.

The following steps are used to determine the histology code.

Open the Multiple Primary and Histology Coding Rules manual. For an endometrial primary, use the Other Sites Histo rules to determine the histology code because endometrium does not have site specific rules.

Start with the MULTIPLE TUMORS ABSTRACTED AS A SINGLE PRIMARY module, Rule H18. The rules are intended to be reviewed in consecutive order within the module from Rule H18 to Rule H31. You stop at the first rule that applies to the case you are processing.

Code the appropriate combination/mixed code (Table 2) when there are multiple specific histologies. GYN malignancies with multiple types of adenocarcinoma have histology coded to 8323/3 [mixed cell adenocarcinoma] per rule H30.

Adamantinomatous craniopharyngioma (9351/1) is a subtype of craniopharygioma. We will correct the Non-Malignant CNS Solid Tumor Rules in the next update.

According to the editors of ICD-O-3, lobular neoplasia grade 2 is not equivalent to LCIS. It is not a reportable term. Lobular neoplasia and lobular intraepithelial neoplasia are equivalent terms having a three grade system. Only LN/LIN grade 3 would be reportable since those terms are analogous to ductal intraepithelial neoplasia grade 3.

According to the World Health Organization (WHO) pancreatic neuroendocrine tumors (NET) are malignant. They are reportable.

For pancreas primaries, code NET, G1 (well differentiated) to 8240/3; NET G2 (moderately differentiated) to 8249/3; and nonfunctional NET, GI or G2 to 8150/3.

The histology code for neuroendocrine carcinoma (NEC) is 8246/3, large cell NEC is 8013/3 and small cell NEC is 8041/3.

According to the WHO Classificationof Tumors of Female Reproductive Organs, 4th edition, MMMT (8950/3) is now a synonym for carcinosarcoma (8980/3) even though it has a separate ICD-O code. The ICD-O code for MMMT is no longer in the WHO book. Per the subject matter experts, when both terms are used in the diagnosis (carcinosarcoma/MMMT), code the histology to 8980/3. If the ONLY term used is MMMT, assign 8950/3.

The information in the 4th edition of the WHO Classification of Tumors of Female Reproductive Organs has not yet been incorporated into the Other Sites Solid Tumor Rules.

According to the MP/H rules, code histology to 8120/3 [urothelial carcinoma] for cases diagnosed 2007 or later. The term "glandular differentiation" is equivalent to adenocarcinoma differentiation. 8120/3 [urothelial carcinoma] would be the best way to code a "biphasic pattern with cautery-distorted urothelial carcinoma and adenocarcinoma" according to a pathologist consultant.

The steps used to arrive at this decision are as follows:

Go to the Urinary Histo rules found in the Multiple Primary and Histology Coding Rules Manual.

Start at the MULTIPLE TUMORS ABSTRACTED AS A SINGLE PRIMARY module, rule H9. Code the histology to 8120 [transitional cell/urothelial carcinoma] when there is transitional cell carcinoma with glandular differentiation.

According to the MP/H rules, code histology to 8010/2 [intraepithelial carcinoma] for cases diagnosed 2007-2014. Borderline mucinous tumor is not reportable to SEER.

The steps used to arrive at this decision are:

Go to the Other Sites Histo rules found in the Multiple Primary and Histology Coding Rules Manual.

Start at the SINGLE TUMOR: IN SITU ONLY module, rule H1. Code the histology when only one histologic type is identified. The only reportable histology in this case is intraepithelial carcinoma [8010/2].

According to the 5th edition WHO Blue Book for Hematopoietic Neoplasms, Beta Version, (not released yet), nodular lymphocyte predominant B-cell lymphoma is an alternate name for 9659/3. We will update the Heme database once the 5th edition is released in print.

According to our subject matter expert, vulvar extramammary Paget neoplasm (intraepithelial glandular neoplasm) represents an in situ malignancy and should be reported.

He states "The traditional terminology should be 'extramammary Paget disease' to describe an in situ adenocarcinoma arising from extramammary glands in vulvar mucosa. I am not so sure about "extramammary Paget NEOPLASM", which may include all three Pagetoid processes: the traditional Paget disease, the Pagetoid spreading of an anal adenocarcinoma and a Pagetoid spreading of an urothelial carcinoma from the urethra. Regardless, all these entities are considered at least in situ carcinomas."

We recommend that you review clinical records and imaging for the clinical scenarios mentioned above.

According to our subject matter expert physician, this unusual case is most likely a sino-nasal tumor (some variant of esthesioneuroblastoma [olfactory neuroblastoma]). Code to nasal cavity [C300] as indicated in ICD-O-3 by site-associated topography code attached to the morphology code for olfactory neuroblastoma [9522/3].