Histology (Pre-2007)--Breast: What code is used to represent histology for "invasive ductal carcinoma with squamous differentiation"? Is "squamous differentiation" synonymous with "squamous metaplasia"?
For tumors diagnosed prior to 2007:
Code the Histology field to 8570/3 [Adenocarcinoma with squamous metaplasia]. Our pathology consultant agrees that squamous metaplasia is synonymous with squamous differentiation.
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.
Reportability--Heme & Lymphoid Neoplasms: If not specified as primary, idiopathic, or essential, is thrombocytosis, NOS reportable?
Updated May 2026
Thrombocytosis, NOS is not reportable for any year of diagnosis.
Unless the disease is specified as primary, idiopathic, essential, or the physician states there is a myeloproliferative neoplasm, the term thrombocytosis, NOS is not reportable. Thrombocytosis, NOS, is the presence of high platelet counts in the blood. Thrombocytosis can be associated with chronic infections and other diseases as well as with myeloproliferative disease.
Histology (Pre-2007)/Terminology: Are "pattern", "architecture", and "architectural pattern" terms that indicate a majority of tumor?
For tumors diagnosed 2004 to 2006:
The terminology "Architectural pattern: ____________," when used in the final pathology diagnosis, indicates a subtype that can be coded. This type of format in a pathology report is based on a College of American Pathologists (CAP) protocol. Disregard "pattern" and "architecture" when not used in accordance with the CAP protocol. See www.cap.org for cancer protocols.
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.
EOD-Extension--Colon: How is this field coded for an appendical primary when the appendix has ruptured and intrapentoneal fluid is positive?
For cases diagnosed 1998-2003: Code EOD extension as 85 [Metastasis]. Positive intraperitoneal fluid is equivalent to distant metastasis (implantation) for colon, including appendix, primaries.
Histology: Are all well differentiated neuroendocrine carcinomas (carcinoid) tumors coded to 8240 or 8246? When do you use code 8246?
Code 8246 is correct when the mass/lesion is referred to as neuroendocrine "carcinoma" or NEC. Use code 8240 when the mass/lesion is referred to as a neuroendocrine "tumor" or NET G1. The difference is the word tumor versus carcinoma. Carcinoid is most often used interchangeably with neuroendocrine tumor and not with neuroendocrine carcinoma.
Surgery of Primary Site--Bladder: Do we code "random bladder biopsies" as an excisional biopsy (27) or as no cancer directed surgery (00) even if the only involvement mentioned on the pathology reports is "focal carcinoma in situ"?
Code the Surgery of Primary Site field to 00 [None; no surgery of primary site] when only random biopsy procedures are performed on the bladder.
First course treatment/Radiation Therapy--Prostate: How do you code fiducial markers for prostate cases?
Do not code fiducial markers as a form of radiation treatment; rather, code the radiation therapy in the radiation treatment section. Fiducial markers are small metal spheres, coils, or cylinders that are placed in or near a tumor to help guide the placement of radiation beams during treatment.
Date of Diagnosis: When doing follow-back at nursing homes on DCO cases, we find it difficult to code diagnosis date because the nursing home records are often vague or incomplete. Should the diagnosis date be coded as unknown (excluded from SEER database), the date of death, or the approximate date of diagnosis as reported on the death certificate?
If the nursing home record indicates that the patient had cancer, use the best approximation for date of diagnosis.
If the record says the patient had cancer when admitted, but it does not provide a date of diagnosis, use the date of admission as the date of diagnosis.
If there is no mention of cancer in the nursing home record and/or all work-up in the record is negative, assume the cancer was discovered at autopsy. Use the date of death as the date of diagnosis, and leave as a Death Certificate Only case.
Histology/Grade, Differentiation--Lymphoma: What code is used to represent the histology "high grade malignant lymphoma with features of so called blastic NK cell cutaneous lymphoma [hematodermic lymphoma]" found on punch biopsy?
For cases diagnosed prior to 1/1/2010:Code the Histology field to 9709/3 [cutaneous lymphoma, NOS]. Code the Grade, Differentiation field to 8 [NK cell].
For cases diagnosed 2010 forward, refer to the Hematopoietic and Lymphoid Neoplasm Case Reportability and Coding Manual and the Hematopoietic Database (Hematopoietic DB) provided by SEER on its website to research your question. If those resources do not adequately address your issue, submit a new question to SINQ.
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