Source 1: ICD-O-3
Source 2: 2018 SEER Manual
Reportability/Histology--Thymus: Is a thymoma a malignancy if described as having separate tumor nodules within peri-thymic adipose tissue? See Discussion.
Patient had a thymectomy including pericardial fat for a mediastinal mass found incidentally during lung screening. Final diagnosis is WHO B3 thymoma. Staging Summary lists transcapsular invasion: "Present, as separate tumor nodules within peri-thymic adipose tissue." Tumor extension is stated to be "Confined to thymus, including peri-thymic adipose tissue." The pathologist staged this resection as pT1a pNX with no mention of mets. Clinically, there are no noted metastatic sites and no further treatment is planned.
Report this case as a malignant thymoma. Our expert pathologist consultant reviewed this case and in his opinion, the "separate tumor nodules within peri-thymic adipose tissue" fit registry reporting criteria for separate tumor nodules making this a malignant thymoma.