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Report Produced: 11/24/2025 07:28 AM

Report Question ID Question Discussion Answer Year
20100063 Primary Site-Lung: Can you use a lung subsite code for a histologically confirmed lung primary when a CT scan indicates a sized mass located in one lobe of the lung as well as "too numerous to count nodules" through one or both lungs? See Discussion. For example, chest CT shows "1.6 cm RUL suspicious mass and too numerous to count nodules throughout both lungs." Core biopsy of mass in the RUL compatible with adenocarcinoma. For lung primaries with one large mass and numerous nodules, code the primary site to the subsite where the large mass is located. For your example, code the primary site to C341 [upper lobe of lung]. Note: This answer does NOT mean that the other nodules are primary or metastatic cancer. 2010
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.

 2006
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. 2006
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.

 2006
20031140 Primary site--Unknown & ill-defined site/Kidney: How should this field be coded when humeral metastases are compatible with renal cell carcinoma pathologically, no kidney lesion is found clinically and the physician's signout diagnosis is "no primary found, as of now unknown"? See Description. Path states "biopsy of humerus, mets sarcomatoid carcinoma consistent with renal cell carcinoma." Material was sent to Mayo Clinic for consult & they state "with focus of clear cells, agree that a likely primary is renal cell carcinoma." Abdominal CT showed no abnormality in kidneys. When the registrar abstracted the case she spoke to the managing physician who told her that "no specific site was found and it was, as of now, unknown." This was stated about three months after dx. Can we code as a renal primary based on pathologic information or should we code unknown based on CT and physician's statement?

Code this case to C64.9 [Kidney, NOS].

ICD-O-3 rule H states that the topography code attached to a morphology term may be used when the topographic site is not given in the diagnosis. Topography code C64.9 is attached to morphology code 8312/3 [Renal cell carcinoma] in ICD-O-3.

 2003
20140005 Primary site--Testis: In the absence of a specific statement that the patient's testicle(s) are descended, should the primary site for a testicular tumor be coded as C621 (Descended Testis) when the mass is palpable on physical exam or demonstrated on scrotal ultrasound? See discussion. It seems the non-specific Testis, NOS (C629) code is being over used. Many testis cases have no documentation of the patient's testicular descention. However, testicular tumors in adults are frequently detected by palpation or scrotal ultrasound. An undescended testis (a testis absent from the normal scrotal position) would be non-palpable or not amenable to imaging via a scrotal ultrasound. Unless the testicle is stated to be undescended, it is reasonable to code C621 for primary site. Reserve C629 for cases with minimal or conflicting information. 2014
20051116 Primary Site--Soft Tissue: How is the primary site coded for a PNET found in the groin when the Tumor Board states the primary is unknown but the SEER site/histology validation table does not allow a site of C809 or C76x to be coded in combination with the histology of 9473/3?

Code site to C495 [connective tissue of pelvis, groin].

This was not called metastatic PNET and no other site of disease is noted. PNET is a broad classification of a group of tumors that usually occur in the CNS and can also occur in soft tissue (neuroblastoma, extra-osseous Ewing sarcoma).

 2005
20051040 Primary Site--Sarcoma: What is the correct topography code for a partial lung lobectomy with pathology diagnosis of "pulmonary sarcoma with smooth muscle differentiation"? See Discussion.

Operative report: palpable 2x2cm mass in the mediastinal surface of the rt middle lobe and the contiguous upper lobe together.

Path comment after partial lung lobectomy: In all likelihood this is a malignant process occurring in smooth muscle changes surrounding vessels within the lung versus an undifferentiated epithelial tumor.

ADDENDUM DX: low grade pulmonary sarcoma with smooth muscle differentiation.

Consultant's report concurs with that of the original pathologist's report of malignant neoplasm compatible with smooth muscle origin.

 This case is unique. Assign topography code C493 [Connective, subcutaneous and other soft tissue of thorax]. Based on the information provided, this sarcoma has smooth muscle differentiation and originated in the muscle. Code the primary site to muscle. 2005
20051096 Primary Site--Peritoneum: During a second look staging lap following a diagnosis of serous carcinoma of the left ovary, did the physician correctly indicate a new peritoneum, NOS primary for disease described as an endometrioid adenocarcinoma in a "paracaval cyst" that appears to have arisen in endometriosis?

The primary site is C482 [Peritoneum, NOS]. "Paracaval" means alongside or near the vena cava.

Code the site in which the primary tumor originated.

 2005
20031137 Primary Site--Pancreas: Should tumors with the histology "islet cell carcinoma" be coded C25.4 [Islet of Langerhans] even though the tumor location is stated to be in head of pancreas? Assign code C25.4 [Islets of Langerhans...Endocrine pancreas]. Islet cell carcinoma of the pancreas is a tumor of the endocrine pancreas. Although Islet cells are present throughout the pancreas, the best code is C25.4 to distinguish endocrine from exocrine cancers. 2003