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Report Produced: 10/07/2026 23:09 PM

Report Question ID Question Discussion Answer Cancer Site Category Data Item Category Year
20240077

2024 SEER Manual/Primary Site--Retroperitoneum: What is the primary site code for a final diagnosis of endometrioid adenocarcinoma from a biopsy of a right retroperitoneal mass? See Discussion. 

An 80-year-old post-menopausal female (status post hysterectomy for benign reasons) presents with a retroperitoneal mass on imaging. The pre-operative imaging shows the cervix and uterus are absent. Patient undergoes a robotic left salpingo-oophorectomy with biopsy of the retroperitoneal mass.

Code Primary Site to C480 (retroperitoneum). 

Endometrial tissue may "break away” from the uterus and implant throughout the pelvic and abdominal cavities. This can occur in patients who suffer from endometriosis. This tissue remains behind when surgical removal of the uterus is done. Common sites of implantation are colon, peritoneum, retroperitoneum, and bladder. These cells may become malignant. When the uterus is no longer present (patient had surgical removal), code the site where the carcinoma was identified.

The site-morphology combination of C480 and 8380/3 was designated as an unlikely site-morphology combination by the Cancer PathCHART expert pathologist review, as this is a rare type of tumor. Assign a value of 1 in the Over-ride Site/Type [2030] data item in order to pass the Primary Site, Morphology-Type, Beh ICDO3, 2024 (SEER) edit.

 Corpus uteri Primary site 2024
20110127

Primary Site--Brain and CNS: Are meninges surrounding cranial nerves cranial meninges [C700] or a part of the specific nerve's sheath? Is the primary site for an optic nerve sheath meningioma coded to optic nerve [C723] or cranial meninges [C700]?

Code the primary site to cranial meninges [C700].

 Brain and CNS Primary site 2011
20031079 Primary Site: Should we code C80.9 [unknown primary] or code C34.9 [Lung] according to the terminology, "most likely site of origin is lung"? See Description.

We have a case of metastatic keratinizing squamous cell ca. The work-up shows small densities in the lung that may represent inflammatory or chronic changes. No other imaging that shows origin. Physical exam states 2 months of left axillary mass. H/O SCCA of the skin involving chest wall.

Path reads: Metastatic w/d keratinizing SCCA. This lesion almost undoubtedly represents mets. The most likely site of origin is lung followed by esophageal primary or head & neck. The final discharge states, "Metastatic SCCA to Left Axilla".

Code the primary site according to the physicians' opinion, especially the treatment decision. If the physician treats the patient for a lung primary, code primary site as lung. If the primary site cannot be determined, code C80.9.

According to the pathologist, the most likely primary site for the example above is lung. The final discharge diagnosis does not reflect the pathologist's opinion, and does not contradict it either. If there is no conflicting medical opinion, code primary site to C34.9 [lung].

 N/A Primary site 2003
20230029

Primary Site--Skin:  Are perianal skin primaries within 5 cm of the anus coded as perianal skin (C44.5) or anus (C21.0).  See Discussion.

ICD-O-3 tells us that perianal skin is C445 and we do not capture basal or squamous cell skin cancers in our registry. The AJCC manual stages perianal skin cancers within 5 cm of the anus with the anus chapter.  We cannot AJCC stage them as an anus if we are not capturing them as C445.  I realize we do not code a site in order to stage. We have been following the reportability rules and not capturing. Is this correct? I do not see this addressed in the new Other Sites Solid Tumor Rules.

Code primary site based on the site of origin as determined by the physicians. If the physicians state the site of origin is anus, code anus; the same as with skin. As you state, squamous cell cancer of sites coded to C44 is not reportable.  The AJCC instruction for physicians to stage perianal neoplasms within 5 cm of the anus using the Anus chapter does not change cancer registry instructions for coding primary site, nor does it affect cancer registry reportability instructions.

 Skin Primary site 2023
20250028

2025 SEER Manual/Primary Site--Lymph Nodes: How is Primary Site coded when lymphangioleiomyomatosis is incidentally diagnosed in pelvic lymph nodes on a resection for an unrelated reason? See Discussion.

Lymphangioleiomyomatosis (LAM) became reportable (9174/3) for diagnoses 2023 and later. While this neoplasm was only added to the Lung schema in the Solid Tumor Rules manual, this is a mesenchymal neoplasm which may arise outside of the lung and the reportability change was not limited to LAM of the lung.

How should primary site be coded when a left pelvic lymph node dissection for an unrelated high-grade serous carcinoma of the right fallopian tube incidentally proved LAM in the pelvic lymph nodes? The pelvic lymph nodes were the only site of involvement; there was no evidence of lung involvement. As this is a mesenchymal tumor, should the primary site default to C499 (Soft tissue, NOS) according to the default primary site rule for sarcomas described in the SEER Manual? Or should the primary site be coded to C775 (Pelvic lymph nodes) as this was the only proven site of involvement?

Code the primary site to pelvic lymph nodes (C775) as it is the only site involved with this extrapulmonary lymphangioleiomyomatosis (E-LAM).

 Fallopian Tube, Lymph nodes Primary site 2025
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. Pancreas Primary site 2003
20180100

Reportability/Primary Site--Skin: Is vulvar intraepithelial neoplasia III (VIN III) or associated invasive squamous cell carcinoma reportable when stated to be of the or or ? See Discussion.

Example: Operative report states, partial simple vulvectomy, anoscopy with normal-appearing clitoris, clitoral prepuce, bilateral labia majora, and labia minora. There is a 1.5 x 1 cm raised, hyperpigmented lesion which appears consistent with VIN 3 on the perineal body, just to the right of midline, and not touching the midline. It goes quite close to the anus but is not touching the anus.

Final diagnosis on resection is, Invasive squamous cell carcinoma arising in a background of high-grade squamous intraepithelial neoplasia (VIN III) with the following features: Location: perineum. Focal invasion arising in setting of 1 cm area of VIN III.

Squamous carcinoma and squamous intraepithelial neoplasia III arising in the skin of the perineum (C445) are not reportable. Even though the abreviation "VIN III" is used in this example, this lesion does not involve the vulva. Since it involves the perineum, and skin of perineum is coded to C445, it is not reportable.

Neoplasms arising in skin (C44) with the following histologies are not reportable.

--Malignant neoplasm (8000-8005)

--Epithelial carcinoma (8010-8046)

--Papillary and squamous cell carcinoma (8050-8084)

--Squamous intraepithelial neoplasia III (8077) arising in perianal skin (C445)

--Basal cell carcinoma (8090-8110)

 Skin Primary site 2018
20210024

Primary Site--Vulva: What is the primary site of patient with an excision of a left vulvar cystic mass showing focal mammary-type ductal carcinoma in situ (DCIS) on 11/06/2020? See Discussion.

Final Pathologic Diagnosis:

Vulvar cyst, excision: Focal mammary-type ductal carcinoma in situ, intermediate grade, arising within cystically dilated duct (See Comment)

Size of DCIS: 0.7 CM.

Margins: Negative.

Comment

Sections demonstrate a cystically dilated duct. Focally, at the periphery of the duct, there is a neoplastic monomorphic proliferation of ductal cells with intermediate grade nuclei. No associated necrosis is identified. Immunostains for GATA-3 and estrogen receptor are strongly positive within the neoplastic cells, supporting origin from mammary-like epithelium. Immunostain for p63 demonstrates preservation of a basal layer around the dilated duct, including the region involved by DCIS. Immunostain for cytokeratin 5/6 shows loss of expression within the DCIS. No stromal invasion is identified. The cyst appears to be completely excised.

12/01/2020 post op visit with surgeon:

Ductal carcinoma in situ (DCIS) of the left vulva in an excised cystic lesion.

PLAN: I reviewed the pathologic findings from the excision of the left vulvar cyst. This appears to be a cystic lesion in the mammary line with focal DCIS. It was excised completely with negative margins. It would not warrant any additional treatment except expectant management.

Code the primary site to vulva. Use text fields to record the details.

According to the WHO classification, several types of primary vulvar mammary-like carcinoma have been reported. It is rare and is thought to arise from specialized anogenital mammary-like glands within the vulva. It does not arise from ectopic breast tissue and is does not represent metastatic breast carcinoma.

 N/A Primary site 2021
20150059

Primary Site--Liver: What is the topography code for combined hepatocellular carcinoma/cholangiocarcinoma (M-8180/3) especially when there is no documentation that intrahepatic bile duct is the tumor site? Reports usually just indicate a liver mass(es) but since the intrahepatic ducts are within the liver, is the code C221 due to the cholangiocarcinoma component, thus making the case stageable?

If there is no further information about where the cancer originated, assign C220. Use ICD-O-3 as the source for coding topography. The topography code associated with combined hepatocellular and cholangiocarcinoma (8180/3) is C220 when there is no other information available, according to ICD-O-3.

N/A Primary site 2015
20120072

Primary site--Heme & Lymphoid Neoplasms: How is the primary site coded for a diagnosis of multifocal Langerhans cell histiocytosis with involvement of the bone, liver, spleen and retroperitoneum?

Updated May 2026

In the Abstractor Notes section in the Heme DB, it indicates the primary site may differ for LCH in the solitary disease and multisystem disease. This patient has multisystem disease with involvement of the bone, liver, spleen and retroperitoneum. The most common sites for multisystem involvement include three of the four above sites (bone, liver, and spleen).

Determine the primary site based on the knowledge of the usual sites of involvement for this disease, the actual sites of involvement for the case presented, and identifying which sites of involvement are likely metastatic and which are the potential primary sites. There are two potential primary sites of involvement: the bone and the retroperitoneum. Bone is a common site of involvement for LCH while the retroperitoneum is not. Code the primary site to C419 [bone, NOS] because multiple bones are involved for this patient and bone is the most common site for LCH based on the documentation in the Abstractor Notes.

The spleen and liver are typically not primary sites for this disease process. They become involved when there is multisystem involvement because they filter the blood. They are typically sites of metastatic involvement.

The Abstractor notes also indicate that if it's not possible to determine primary site for LCH, default to Bone, NOS (C419)

 Heme & Lymphoid Neoplasms Primary site 2012