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Report Produced: 10/07/2026 03:02 AM

Report Question ID Question Discussion Answer Cancer Site Category Data Item Category Year
20031112

Primary Site/Histology (Pre-2007)--Unknown & ill-defined site: How are these fields coded for a markedly atypical high grade malignant neoplasm diagnosed by a fine needle aspiration of a large iliac mass, right buttock area? See Description.

The diagnosis was made in Oct. 2002 by a CT guided fine needle aspiration of a large iliac mass, right buttock area. The cytology report says:

a. positive for malignant cells, markedly atypical high grade malignant neoplasm.

b. It is impossible to tell from this aspiration biopsy whether or not this represents a high grade sarcoma or a high grade carcinoma, but our consensus opinion is that this lesion is a high grade carcinoma.

The combination of soft tissue topography and carcinoma morphology is Impossible by SEER edits. How should we code this?

For tumors diagnosed prior to 2007:

Code the site to C76.3 [Pelvis, NOS]. Code the histology to 8010/34 [Carcinoma, NOS, high grade].

Unless there is better information available regarding the site, assign C76.3. The information provided above does not indicate the exact site of the mass.

Code the histology based on the consensus opinion stated above.

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.

 Unknown & ill-defined sit Histology, Primary site 2003
20061068 Primary Site--Unknown & ill-defined site: Should the primary site be coded to C809 [Unknown primary site] or C761 [Thorax, NOS] if the patient died following a limited work-up that included on a cytology on pericardial fluid that was positive for poor differentiated adenocarcinoma? Based on the information provided, code the primary site to C809 [Unknown primary site]. There is not enough information provided to suggest that the primary site is the thorax or any other location. Unknown & ill-defined sit Primary site 2006
20010118 All Surgical Fields/Radiation Sequence with Surgery--Unknown Primaries: What codes are used to represent these fields for an unknown primary treated with a radical neck dissection followed by radiation therapy?

For unknown primaries treated with a lymph node dissection and diagnosed 1/1/2003 and after, code:

1) Surgery to Primary Site: 98 [All unknown and ill-defined disease sites, WITH or WITHOUT surgical treatment].

2) Scope of Regional Lymph Node Surgery: 9 [Unknown or not applicable].

3) Surgical Procedure of Other Site: 1 [Surgery to other site(s) or node(s), NOS; unknown if regional or distant].

4) Radiation Sequence with Surgery: 3 [Radiation after surgery]. Any planned surgical treatment is used to code radiation/surgery sequence (per CoC I&R).

 Unknown & ill-defined sit Radiation Therapy 2001
20081028 Multiplicity Counter--Ill-defined sites: How is this field coded for Ill-Defined sites (C760-C768)? Code the number of tumors present if known. If the number of tumors present is not known, code 99 [unknown number of tumors, unknown if multiple tumors]. Unknown & ill-defined sit N/A 2008
20061034 Primary Site--Unknown & ill-defined site: Is the primary site code C809 [Unknown primary site] preferred over the use of a site code for an organ system (e.g., biliary tract, NOS) or a specific primary site (e.g., colon, NOS) when these are "favored" but other potential sites "cannot be excluded"? See Discussion.

Case 1 - CT: Mult pulm nodules, bilat pleural effusions; paraaortic, paracaval, celiac lymphadenopathy. Lytic lesions L4&L5.

Bx L3: Met pd adenoca. Based on the histopathologic features and the results of the immunostains, cholangiocarcinoma is regarded as the most likely primary. However, other possible primaries include pancreas, stomach, and (remotely) lung.

Should primary be coded as C26.9, digestive organ, NOS?

Case 2 - CT: Mult liver masses. Liver Bx: Mod diff adenoca. The most likely primary sites include cholangiocarcinoma, stomach and pancreas.

FDx per attending: Met adenocarcinoma to the liver, probably biliary origin.

What primary site code do we use?

Case 3 - Admitting Dx: Unknown primary with mets to lungs, liver and cerebellar area. Liver Bx: Met adenoca. The combination of morphological and immunohistochemical staining favor a colon primary. However other possibilities include cholangiocarcinoma and pancreatic ca.

Should we code site as C18.9 or C26.9?

Code the primary site according to the physician's opinion. An ill-defined site code or an NOS code for the organ system is preferred over C809 [Unknown primary site] whenever possible. Code C809 only when there is not enough information to use an ill-defined or NOS code.

Case 1 and Case 2 - Assign code C249 [Biliary tract, NOS]. Based on the available information, the physicians believe these are most likely biliary primaries.

Case 3 - Assign code C189 [Colon]. According to the available information, the physician believes this is most likely a colon primary.

 Unknown & ill-defined sit Primary site 2006
20031113 Primary site/Surgery of Primary Site/Surgical Procedure of Other Site--Unknown & ill-defined site: How are these fields coded for this type of primary site when a tumor excision and lymph node dissection is performed? See Description. Patient had a left parotidectomy w/ neck dissection in 02/2003. Findings showed a 10x5cm neck mass over the angle of the mandible as well as a 1.5 cm level 4 mass. Path showed invasive mod diff squamous cell ca. with posterior soft tissue margin positive for tumor; small portion of salivary gland had no tumor. Metastatic SCCa in 5 of 34 lymph nodes of neck dissection; no tumor in parotid lymph nodes. Pathology report says this could be a parotid carcinoma because the bulk of the disease is in the parotid, but it could also be metastatic...correlate with clinical findings. Doctor calls this unknown primary of the head and neck. Is this C80.9 or C76.0?

For cases diagnosed 1998-2003: The data item "Surgery of Primary Site" is intended to record only surgeries of the primary site. If the primary site is unknown or ill-defined, it is impossible to determine whether or not a particular surgery was performed on the primary site. "Surgical Procedure of Other Site" collects much less specific information; however, this is the correct data item to record surgery performed when the primary site is unknown or ill-defined.

For the case example, code the primary site as C76.0 [Head, face or neck, NOS]. Code Surgery of Primary Site as 98 [All unknown and ill-defined disease sites, with or without surgical treatment]. Code Surgical Procedure of Other Site as 1 [Non-primary surgical procedure performed].

 Unknown & ill-defined sit Primary site, Surgery of Primary Site 2003
20051077 First Course Treatment--Unknown & ill-defined site: We have a case with an unknown primary site and the patient had chemoembolization into the hepatic artery. We don't know how to code this treatment. See Discussion. We were told to code as surgery (10) and chemo (01). However an unknown primary automatically gets a (98) surgery code & the chemo is coded (01) but we can't code as systemic therapy. This is an edit. Chemo coded but no date of systemic therapy.

Effective for cases coded prior to the change in policy made on January 9, 2008, code chemoembolization of a metastatic site as 1 [nonprimary surgical procedure performed] in Surgical Procedure of Other Site.

Surgery of Primary Site code 98 is assigned to all cases with an unknown primary.

In the case of a liver primary, it would be coded 10 [local tumor destruction, NOS] in Surgical Procedure of Primary Site.

 Unknown & ill-defined sit First course treatment 2005
20061118 Primary Site--Unknown & Ill-defined Site: What is the primary site code for multiple malignant rhabdoid tumors (extra renal) in a newborn infant?

Search for additional information on the location of the primary in this case. A tissue specimen (biopsy) is required for a diagnosis of rhabdoid. Additionaly, there should be scans describing any tumors located in sites other than the biopsy site. If the biopsy site is not assumed to be a metastatic site and is the only location of tumor, code the site of the biopsy as the primary site.

If it is not possible to obtain further information for this case, code the primary site C809 [Unknown primary site].

According to our pathologist consultant, extra-renal rhabdoid tumors have been described in organ sites (liver, GI tract, thyroid, CNS, skin, to name a few) as well as in the soft tissue. Many of the organ site tumors are multiple/multifocal, so multiple tumors in one organ do not necessarily imply metastatic disease and therefore unknown primary site.

 Unknown & ill-defined sit Primary site 2006
20091027 MP/H Rules/Multiple primaries--Thyroid: How many primaries should be coded in a patient with a 4/5/08 left thyroid lobectomy diagnosis of follicular carcinoma followed by a 7/25/08 right thyroid lobectomy diagnosis of papillary carcinoma, follicular variant?

For cases diagnosed 2007 or later:

Rule M17 under Other Sites applies. These are separate primaries based on their ICD-O-3 histology codes. Follicular carcinoma is coded 8330. Papillary carcinoma, follicular variant is coded 8340. The histology codes are different at the third number. Rule M6 does not apply because these diagnoses are more than 60 days apart.

 Thyroid N/A 2009
20081041 MP/H Rules/Histology--Thyroid: How many primaries are to be reported and what histology is to be coded for an anaplastic/undifferentiated thyroid carcinoma with sarcomatoid transformation likely arising in association with a papillary thyroid carcinoma? Thyroid contains one tumor: 12.5 cm in greatest dimension...almost completely replaces entire thryroid gland.

For cases diagnosed 2007 or later:

This is a single primary using rule M2; a single tumor is always a single primary.

The histology code for this case is 8260/3 [Papillary carcinoma of thyroid]. Begin with Histology Coding rule H8. Stop at rule H17 and code the histology with the numerically higher ICD-O-3 code.

 Thyroid Histology 2008