Source 1: Subject matter expert
Reportability/Histology--Appendix: Is high grade appendiceal mucinous neoplasm (HAMN) diagnosed in 2018 reportable? See Discussion.
Example: Initial CT scan impression is large appendiceal mucocele with a moderate amount of right-sided abdominal ascites. Faint mural enhancement suggesting an underlying appendiceal neoplasm (mucinous adenoma or adenocarcinoma).
Appendectomy follows two days later with final diagnosis of high-grade appendiceal mucinous neoplasm, see comment. Histologic grade: Grade G2 of 4 (based on the CAP protocol) . . . Ascites fluid (ThinPrep(r) and cell block preparations): Mucin, fragments of debris, and macrophages. No diagnostic neoplastic cells are identified . . . Pathologic stage: pT4a, pNX, pM1a (AJCC 8th ed).
Diagnosis Comment states, We feel that there are areas of this tumor where the cytologic atypia is beyond what one would expect in low-grade appendiceal mucinous neoplasm. While mitotic figures are not strikingly increased, there are focal nuclear changes that would support classification of this tumor as high-grade appendiceal mucinous neoplasm.
Approximately two weeks later the patient has an Oncology assessment stating new diagnosis of T4a, NX, M1a, Stage IVA high-grade mucinous adenocarcinoma of the appendix with mucinous ascites. Patient has had an appendectomy but no further surgery so far. However, anecdotally, the best reported case series has been with surgical debulking followed by HIPEC chemotherapy In that instance I have recommended surgery with intraperitoneal chemotherapy.
Is this a reportable malignancy? If so, what is the best histology for the diagnosis?
HAMN is reportable. Assign 8480/3 for the histology/behavior for this case based on the information provided. According to our expert pathologist consultant, high grade appendiceal mucinous neoplasm places this tumor in the mucinous adenocarcinoma, 8480/3, category.