The CD44v6-negative phenotype in high-grade uterine carcinomas correlates with serous histologic subtype

Uterine serous carcinomas (USCs) and poorly differentiated (International Federation of Gynecology and Obstetrics Grade 3) endometrioid adenocarcinomas (ECs) are two histologic subtypes of high-grade uterine carcinoma that differ in clinical presentation, patterns of dissemination, and biologic aggressiveness. To investigate the mechanisms responsible for this heterogeneity, we studied CD44 and CD44v6 expression in a series of 20 USCs and 21 poorly differentiated ECs. CD44 is a protein involved in cell adhesion and lymphocyte homing, and one of its isoforms, CD44v6, might be related to capillary-lymphatic space invasion and metastasis. Eight (40%) of 20 USCs expressed CD44, compared with 18 (86%) of 21 ECs (P < .005). None of the USCs were reactive with antibodies against CD44v6, whereas 45% of the ECs were immunoreactive (P < .001). CD44v6 expression was observed in the myoinvasive ECs but was not seen in foci of capillary-lymphatic space invasion in either the ECs or the USCs. In summary, the USCs were significantly more likely to demonstrate a CD44- and CD44v6-negative phenotype than were the poorly differentiated ECs.