Table 4. Differentiating mucinous carcinomas of primary vs. metastatic origin.

Feature	Primary	Metastatic
Pathological pattern	Intracellular mucin (>50%), in at least 90% of tumor cells Complex papillary pattern	Abundant extracellular mucin, in 50% or greater tumor volume Nodular pattern
Involvement	Coexistence of borderline/benign mucinous component Expansile pattern of invasion	Ovarian surface involvement Hilar involvement Vascular invasion Extensive infiltrative pattern of invasion
Size and distribution	Unilateral Size >10 cm	Bilateral Size <10 cm
Markers	CA125 CEA >25	Elevation may be present, although less than in colorectal primary cancers
Molecular alterations	KRAS mutations: 43% BRAF mutations: 0% HER2 amplification: 18%	KRAS mutations: 30% BRAF mutations: 20% HER2 amplification: <1%

CEA, carcinoembryonic antigen; HER2, human epidermal growth factor receptor 2.