An official website of the United States government
Home
SEER Inquiry System - Report
Produced: 05/21/2026 1:52 PM
Question 20250028
Inquiry Details
References:
2025 SEER Manual, 108-113. Primary Site
Question:
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.
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?
Answer:
Code the primary site to pelvic lymph nodes (C775) as it is the only site involved with this extrapulmonary lymphangioleiomyomatosis (E-LAM).
