The clinical significance of K-ras mutation in endometrial "surface epithelial changes" and their associated endometrial adenocarcinoma

The entity of 'surface epithelial changes' (SECs) was first described in 1995 [1]. Morphologically, SECs usually arise from malignant glands at the superficial aspect of well differentiated (WD) endometrioid carcinomas (ECs) and impart the appearance of a 'maturational' phenomenon at the surface of the cancer. Exhibiting a paradoxically bland histologic appearance, SECs typically show morphologic features that mimic benign entities, particularly endocervical microglandular hyperplasia (MGH). SECs have been associated with approximately half of WD endometrioid carcinomas many of which showed focal mucinous differentiation. Despite their morphologically benign histology, some have questioned whether the presence of SECs represents a 'marker' for an underlying malignancy, especially in postmenopausal women with endocervical or MGH-type SECs in their endometrial sampling. Since the biologic nature of SECs is unknown, we aimed to study the prevalence of KRAS gene mutations in SECs and the underlying WD endometrioid adenocarcinomas (EC) from which they directly arise.

24 cases with biopsy proven SECs and ECs in their subsequent hysterectomy were retrieved. Genomic DNA was extracted from formalin-fixed paraffin-embedded tissue. PCR amplification for KRAS codons 12 and 13 was performed, followed by sequencing using capillary electrophoresis.

KRAS codons 12 and 13 mutations were detected in 19 of 24 (79%) SECs, and 19 of 24 (79%) ECs. All SECs had the same KRAS mutation as the underlying EC.

Our results suggest that SECs are of neoplastic origin and that KRAS mutations play an important role in the tumorigenesis of ECs and SECs.