MP/H Rules/Histology--Head & Neck: Please clarify rule H3. The first statement is "Do not code terms that do not appear in the histology description". The second statement is "Do not code...unless the words...appear in the final diagnosis"
One of our pathology labs frequently will state "keratinizing squamous cell" in the microscopic description (histologic description), but only state "squamous cell carcinoma" in the final diagnosis. May we code from the histologic description if it's not in the final diagnosis?
Follow rule H3 and code squamous cell carcinoma for these cases unless you can obtain confirmation that these cases should be coded keratinizing squamous cell carcinoma from the lab and/or pathologist. Document this confirmation in your policies and procedures.
The MP/H rules were written with input from leading pathologists in each specialty area. Based on their expert opinion, we instruct registrars to code histology based on the information in the final diagnosis. The microscopic description may contain other terms, but the pathologist lists only the pertinent terms in the final diagnosis.
Multiple Primaries (Pre-2007)--Head & Neck: How many primaries are represented when a1998 invasive squamous cell carcinoma of the true vocal cord is followed by a 1999 diagnosis of in situ squamous cell carcinoma of the true vocal cord (called "recurrent" by the clinician), and in 2001 there is another invasive squamous cell carcinoma of the true vocal cord (no statement of recurrence)? Would your answer be any different if no statement of "recurrent" had been made in 1999?
For tumors diagnosed prior to 2007:
Code this case as two primaries, an invasive true vocal cord primary in 1998 and another invasive true vocal cord primary in 2001.
If there had been no statement of recurrence for the 1999 in situ diagnosis and the 1999 diagnosis was more than two months following the 1998 diagnosis, this case would be coded as three primaries.
For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.
MP/H Rules--Bladder: Is a TURBT in 4/07 that demonstrates papillary carcinoma (8130/3) followed two weeks later with biopsies that demonstrate high grade flat dysplasia/carcinoma in situ (8010/2) two primaries?
For cases diagnosed 2007 or later, rule M6 applies and this is a single primary.
Flat transitional cell carcinoma and carcinoma in situ of the bladder are synonymous. See the definition of "Flat Tumor (bladder)/Noninvasive flat TCC" in the Urinary Terms and Definitions section of the 2007 MP/H manual.
EOD-Extension--Small Intestine: How do we interpret a pathology description of "extending through serosa and forming masses in the periserosal tissue" for a jejunum primary?
For cases diagnosed 1998-2003:
Code the EOD-Extension field to 55 [Invasion of/through serosa and adjacent connective tissue]. The description states the tumor extended through the serosa into periserosal tissue. The periserosal tissue in this case refers to adjacent connective tissue lying exterior to the intestinal wall and not the (sub)serosal tissue that lies exterior to the muscularis but inferior to the serosa. Analyze each case individually since pathologists are not consistent when using the above terminology.
Grade/Histology--Digestive System: What is the grade for neuroendocrine tumor (NET) or neuroendocrine carcinoma (NEC) of gastrointestinal morphologies described as: 1) NET G1 (M8240/3) and NET G2 (M8249/3) or 2) neuroendocrine carcinoma, low grade (M8240/3) and neuroendocrine carcinoma, well differentiation (M8240/3) and neuroendocrine carcinoma, moderate differentiation (M8249/3)? The SEER Instructions for Coding Grade for 2014+, Coding for Solid Tumors section, #3 state: Code the grade shown below (6th digit) for specific histologic terms that imply a grade. NET and NEC are not included in the specific terms.
You may code grade as follows.
Grade 1 – NET G1 (M8240/3)
Grade 2 – NET G2 (M8249/3)
Grade 1 – neuroendocrine carcinoma, low grade (M8240/3) or neuroendocrine carcinoma, well differentiation (M8240/3)
MP/H/Histology--Thyroid: What is the histology code for primary site of thyroid cancer with the histology of papillary thyroid carcinoma, classical and oncocytic type?
Code the histology to 8342/3, thyroid oncocytic (oxyphillic) papillary carcinoma.
EOD-Extension--Lymphoma: Would a lymphoma involving mesenteric and retroperitoneal nodes (both site code C77.2) be coded to extension 10 [Involvement of a single lymph node region; Stage I], based on the fact that while more than one "chain" is involved only one "region" is involved?
For cases diagnosed 1998-2003:
Code the EOD-Extension field to 20 [Involvement of two or more lymph node regions on the same side of diaphram]. The AJCC lists mesenteric as a core nodal region, but does not list retroperitoneal lymph nodes as a part of this region, so retroperitoneal is a separate region.
The EOD staging scheme for lymphoma uses lymph node REGIONS as the criteria for assigning the extension code. Use the AJCC Cancer Staging Manual as the definitive source for classifying lymph node regions, not the ICD-O-3. If it is a separate LN region per the AJCC, it is coded in the EOD as a separate region.
According to the AJCC curator, the nodal regions are defined in Kaplan's book on Hodgkin disease. Bilateral cervical, or axillary, or hilar, or pelvic, or inguinal nodes count as two regions. Mediastinal and para-aortic lymph nodes count as one region regardless of laterality as they are centrally located. A large mediastinal mass constitutes one region involved regardless of the size.
Reportability--Heme & Lymphoid Neoplasms: Is the term "thrombocytopenia" equivalent to the term "refractory thrombocytopenia" and should be a subsequent primary if it follows a treated diagnosis of pancreatic cancer?
Updated May 2026
Thrombocytopenia NOS is not a reportable diagnosis for any diagnosis year. Thrombocytopenia and Refractory Thrombocytopenia are not the same disease.
Thrombocytopenia is caused by a decreased number of platelets in the blood. Non-malignant causes include disseminated intravascular coagulation (DIC), drug-induced non-immune thrombocytopenia, drug-induced immune thrombocytopenia, hypersplenism, immune thrombocytopenic purpura (ITP), thrombotic thrombocytopenic purpura, and infections of the bone marrow.
Histology (Pre-2007): What code is used to represent the histology for a "malignant invasive gastrointestinal stromal tumor (GIST)"?
For tumors diagnosed 2001-2006: Malignant GIST is coded 8936/3.
For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.
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