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SEER Inquiry System - Report
Produced: 08/21/2025 6:54 PM
Question 20041080
Inquiry Details
References:
#1: ICD-O-3
#2: CS Manual,Part II, 603. Vers 1.1, Aug. 12, 2004
Question:
Behavior Code/CS Extension--Brain and CNS: How are these fields coded when the final diagnosis on pathology indicates that an atypical meningioma invades the brain and the bone flap specimen indicates extensive invasion through the full thickness of the calvarium? See Discussion.
Discussion:
FDx on the path is: A. Rt frontotemporal brain tumor: Atypical meningioma, WHO grade II (out of III). B. Arachnoid tissue: Atypical meningioma with small focus of invasion into superficial brain and focal perivascular spread. C. Bone flap: Atypical meningioma with extensive invasion through full thickness of the calvarium.
Comment: Although this tumor shows a small focus of brain invasion, it should be considered a grade II (out of III) meningioma based on its histologic atypia (cellularity, sheeting of tumor cells and prominent nucleoli), elevated Ki-67 index and low mitotic rate.
Answer:
This answer was provided in the context of CSv1 coding guidelines. The response may not be used after your registry database has been converted to CSv2.For tumors diagnosed prior to 2004, the example above is a benign meningioma and not reportable to SEER.
For tumors diagnosed 2004 or later, code the behavior as 1 [Borderline malignancy]. Code CS Extension as 05 [Benign or borderline brain tumors].
According to expert consultant, meningiomas are in the lining cells for the inner table of the skull and as such have an affinity for bone that allows them to penetrate adjacent bone without being "malignant.
