Comparative immunohistochemical and molecular analysis of uterine and extrauterine leiomyosarcomas

Histologic criteria defining malignancy in smooth muscle tumors are currently site specific. This study was undertaken to determine whether, in leiomyosarcomas (LMS) occurring in different anatomic locations, there were differences in patterns of expression of molecules that have been demonstrated to be associated with biologically aggressive behavior in malignant neoplasms, and also to determine their diagnostic utility. Formalin-fixed paraffin-embedded tissue blocks were selected from 16 extrauterine leiomyosarcomas (EULMS), 14 cases of uterine leiomyosarcomas (ULMS) and from five cases each of uterine and extrauterine leiomyomas (LM). Utilizing immunohistochemical (ABC) techniques with antigen retrieval, we assessed serial sections of each tumor for immunoreactivity with Glut1, CD44s, bcl2, cyclin D1, and estrogen receptor. Molecular genotyping for detecting k-ras-2 point mutation, p53 gene loss, and mdm2 gene amplification was performed on microdissected tumor samples from the same histologic sections. All of the uterine and extrauterine LM were diffusely positive for CD44s, bcl2, and cyclin D1, and uniformly negative for Glut1. In contrast, 50% of the ULMS and 25% of EULMS were Glutl positive. Moreover, Glut1 positivity closely correlated with aggressive biologic behavior reflected by distant metastatic spread. Eighty-percent of LM and 70% of the ULMS were estrogen receptor positive, whereas only one retroperitoneal tumor had focal weak positivity. Over 80% of the extrauterine and 50% of the uterine sarcomas showed absence of CD44s immunoreactivity. Percentage of cyclin D1 immunoreactivity was independent of tumor grade and inversely proportional to the percent of bcl2 positivity. An LMS of the male breast contained k-ras-2 exon 1 point mutation (codon 12 aspartate substitution of glycine). P53 allelic imbalance was present in 29% of ULMS and 57% EULMS. Mdm2 amplification was present in three of six EULMS but not in ULMS. In addition to clinical staging, Glut1 positivity together with patterns of immunoreactivity of CD44 and bcl2 may be helpful in identifying aggressive smooth muscle tumors of the uterus and some EULMS. The presence of estrogen receptor staining may be helpful in identifying uterine versus nonuterine LMS. Although sample numbers are too small for definite conclusions, this study suggests that there are differences in glucose transport, expression of adhesion molecules, and estrogen receptors in ULMS and EULMS, which in part may be due to the estrogen dependency of the ULMS. P53 mutations and mdm2 amplifications appear to be more frequent in EULMS.