The diagnosis of uterine
smooth muscle tumors including
leiomyosarcomas (LMS),
smooth muscle tumors of uncertain malignant potential (STUMP), bizarre (atypical)
leiomyoma (BLM), mitotically active
leiomyoma (MAL) and
leiomyoma (LM) depends on a combination of microscopic features, such as mitoses, cytologic atypia, and coagulative
tumor cell
necrosis. However, a small number of these
tumors still pose difficult diagnostic challenges. The assessment of accurate mitotic figures (MF) is one of the major parameters in the proper classification of uterine
smooth muscle tumors. This assessment can be hampered by the presence of increased number of apoptotic bodies or pyknotic nuclei, which frequently mimic mitoses. Phospho-
histone H3 (PHH3) is a recently described immunomarker specific for cells undergoing mitoses. In our study, we collected 132 cases of uterine
smooth muscle tumors, including 26 LMSs, 16 STUMPs, 30 BLMs, 30 MALs and 30 LMs. We used mitosis specific marker PHH3 to count mitotic indexes (MI) of uterine
smooth muscle tumors and compared with the mitotic indexes of
hematoxylin and
eosin (H&E). There is a positive correlation with the number of mitotic figures in H&E-stained sections and PHH3-stained sections (r=0.944, P<0.05). The ratio of PHH3-MI to H&E-MI has no statistically significant difference in each group except for LMs (P>0.05). The counting value of PHH3 in LMSs have significantly higher than STUMPs, BLMs, MALs and LMs (P<0.001) and the counting value of PHH3 is 1.5±0.5 times of the number of mitotic indexes in H&E. To conclude, our results show that counting PHH3 is a useful index in the diagnosis of uterine
smooth muscle tumors and it can provide a more accurate index instead of the time-honored mitotic figure counts at a certain ratio.