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Mature teratomas in the ovary are benign [9080/0].

For testis, mature teratoma in an adult is malignant (9080/3); however, mature teratoma in a child is benign (9080/0).

With regard to the thyroid issue, from the information above, the medullary carcinoma in the patient's thyroid is clearly a separate event. According to our expert pathologist consultant, "thyroid tissue is one of the many tissue types that may be seen in teratomas. When the teratoma has exclusively or predominantly thyroid tissue the term struma ovarii is used Adenoma or carcinoma of the thyroid type may be seen in this thyroid tissue. If medullary carcinoma were present in the thyroid tissue in the ovary/teratoma, there would be mention of it in the path report."

The case in 20130176 is adult granulosa cell tumor. The answer points out an important difference in the way "metastases" from this histology should be interpreted versus low malignant potential ovarian epithelial tumors. Metastases from adult granulosa cell tumor of the ovary indicates a malignant primary. So-called metastases from a LMP epithelial tumor do not indicate a malignant primary when the metastatic deposits are also LMP/borderline in behavior.

Do not apply instructions for ovarian cases to other primary sites including appendix.

Malignant granulosa cell tumor is reportable. The case described above is malignant as proven by metastasis to the lymph node.

Based on the information provided, this case of adult granulosa cell tumor is malignant and reportable. According to our expert pathologist consultant, "though granulosa cell tumor NOS/ adult NOS is 8620/1, the presence of peritoneal implants or metastases, and/or lymph node metastases indicates the tumor is malignant, and it should be coded /3."

Note that the presence of implants or metastases does not indicate malignancy in the case of low malignant potential ovarian epithelial tumors. Our path expert explains "in contrast, by convention the behavior of borderline/LMP ovarian epithelial tumors is determined by the ovarian primary, and is /1, even though there may be peritoneal implants/metastases, or metastatic disease in lymph nodes. The treatment may vary in these circumstances, but to my knowledge the decision as to the tumor designation remains based on the primary tumor."

Ovarian serous borderline tumor with node implants is not reportable; it is a borderline neoplasm. However, if the oncologist believes he or she is dealing with a low grade serous carcinoma rather than a borderline tumor, this case is reportable. We recommend that you determine whether the diagnosis of low grade serous carcinoma, chemotherapy not recommended, is based on the pathological findings or on something else before reporting this case.

Noninvasive low grade (micropapillary) serous carcinoma (MPSC) of the ovary is reportable. Assign code 8460/2, applying the ICD-O-3 matrix concept to this noninvasive carcinoma. Noninvasive can be used as a synonym for in situ, ICD-O-3 behavior code /2. See page 66 in the softcover ICD-O-3. Low malignant potential (LMP) means that the neoplasm is not malignant, but has some chance of behaving in a malignant fashion. LMP can be used as a synonym for ICD-O-3 behavior code /1, see page 66.

Updated December 2025

For an ovarian mucinous borderline tumor, the term "microinvasion" is not an indication of malignancy according to the WHO Female Genital Tumors, 5th edition, and our expert pathologist consultant agrees. Therefore, borderline mucinous ovarian tumor with microinvasion is not reportable. Low malignant potential/borderline ovarian tumors are defined by the pathology of the primary tumor in the ovary, and microinvasion there, or invasion in implants does not change that diagnosis. The only exception is when the lymph nodes are positive for malignancy, the case is reportable. If the lymph nodes are positive for mucinous borderline tumor, the case is not reportable.

Similarly, serous borderline tumor with microinvasion, unless the morphology resembles low grade serous carcinoma and invasion measures <5 mm in a single focus, is not reportable.

Solid pseudopapillary neoplasm of the pancreas is reportable. According to the WHO classification, it is a "low-grade malignant neoplasm…[which] frequently undergoes hemorrhagic-cystic degeneration and occurs predominantly in young women."

Assign topography code C25 with the appropriate 4th digit. Code the histology as 8452/3.

"Cystic pancreatic endocrine neoplasm (CPEN)" is reportable. Assign 8150/3 based on the information provided. We consulted our expert pathologist and he states "Since metastases have been reported in a few, and all the rest of the pancreatic endocrine tumors are now designated malignant, …we are safe considering them /3 until proven otherwise. Since most of them are non-functioning, [assign code] 8150/3 unless specified as to G1 (8240/3) or G2 (8249/3)."