LAUSR

A variety of terminologies and grading systems have been proposed for classifying primary appendiceal mucinous neoplasms and their metastatic disease (mucinous carcinoma peritonei or pseudomyxoma peritonei). These myriad classification schemes and persistent pathologic ‘‘grey zones’’ have led to significant confusion in pathologic reporting and subsequent clinical management by surgical/medical oncologists. Some of the confusing and controversial pathologic aspects (‘‘grey zones’’) include (1) differentiation of ‘‘pushing’’ invasion (expansile or diverticulum-like growth seen in low-grade disease) from infiltrative ‘‘destructive’’ invasion (seen in high-grade disease), (2) reporting of high-grade histology without infiltrative ‘‘destructive’’ invasion as a neoplasm versus invasive adenocarcinoma (especially when the entire appendix has not been submitted for review), (3) challenges with interpreting the degree of cytologic atypia in binary fashion (low versus high grade) since atypia occurs on a continuum, and (4) questionable signet ring cells versus signet ring cell morphology due to cellular degeneration. PRESENT