Low-grade appendiceal mucinous neoplasm. Cross examination shows a 3-cm cystic, mucin-filled mass at the appendiceal tip (A) and frozen sections reveal paucicellular mucin pools with bland mucinous epithelium, similar to that seen in the ovary, with fibrosis and calcifications (B) (hematoxylin-eosin, original magnification X40 [B]).
Gross and Microscopic Features of Primary and Metastatic Mucinous Carcinomas of the Ovary Primary Metastatic Bilaterality Rare Common (a) Size <10 cm Rare Common (a) Surface involvement Rare Common Lymphovascular invasion Rare Common Hilus involvement Rare Common Growth pattern Predominantly Infiltrative expansile Multinodularity Rare Common Single-cell infiltration Rare May be present Signet ring cells Rare (in teratoma- May be present associated tumors) (a) Most common exceptions: colorectal, endocervical, and appendiceal (low-grade appendiceal mucinous neoplasm) primaries.
In addition, the Eighth Edition of the American Joint Committee on Cancer (AJCC) Cancer Staging Manual was published in 2017 with important changes in the staging of low-grade appendiceal mucinous neoplasms (LAMNs) (11).
Significance of proximal margin involvement in low-grade appendiceal mucinous neoplasms. Arch Pathol Lab Med 2015; 139: 518-21.
Low-grade appendiceal mucinous neoplasm
. The appendiceal lumen is lined by a villous proliferation of mildly atypical mucinous epithelial cells (hematoxylin-eosin, original magnification X200).
Tumors with low-grade cytology were termed low-grade appendiceal mucinous neoplasms
. High-grade lesions limited to the appendiceal mucosa were termed noninvasive mucinous cystadenocarcinomas, whereas peritoneal deposits containing overtly malignant cells were labeled as invasive mucinous adenocarcinomas.
(64-66) In contrast, SATB2 is frequently expressed in low-grade appendiceal mucinous neoplasms
(Figure 2, C and D).