[1174] PTEN and P16 Expression Highlights Atypia and Malignant Transformation in Smooth Muscle Tumors of the Uterus

Mirka W Jones, Rohit Bhargava, David J Dabbs, Onisko Agnieszka, Giuliana Trucco. University of Pittsburgh, Pittsburgh, PA

Background: Tumor supressor genes prevent uncontrolled cell proliferation and provide genetic stability through regulation of cell cycle and promotion of apoptosis. Alteration of tumor supressor gene function either by deletion, mutation or an epigenetic event leads to tumor development. Immmunohistochemical expression of tumor suppressor genes can help in detection of malignant transformation in various tumors. We analyzed the differences in immunohistochemical expression of PTEN and p16 in 74 smooth muscle tumors of the uterus, including leiomyomas, atypical leiomyomas and leiomyosarcomas.
Design: 40 leiomyosarcomas, 12 atypical leiomyomas and 22 leiomyomas from the files of the Department of Pathology, Magee Womens Hospital of UPMC were reviewed and representative sections were immunostained with PTEN and p16 antibodies. Immunohistochemical staining was graded semi-quantitatively by considering the percentage and the intensity of the staining of tumor cells. The H score was obtained by applying the following criteria: H score = 1 X % of weakly (1+) staining cells + 2 X % of moderately (2+) staining cells + 3 X % of strongly (3+) staining cells. The H score ranged from 0 (no immunoreactivity) to 300 (highest immunoreactivity).
Results:

H Scores of PTEN and P16 in LM, ALM and LMS
Tumor/MarkerRangeMeanMedian
LM/PTEN10-22010495
LM/P160-1203015
ALM/PTEN150-300210250
ALM/P1630-280183190
LMS/PTEN30-300200215
LMS/P160-300235280
LM; leiomyoma; ALM; Atypical Leiomyoma; LMS; Leiomyosarcoma

Atypical leiomyomas and leiomyosarcomas show no statistically significant difference in staining pattern for PTEN and p16 (p value= 0.387 for PTEN and p value=0.153 for p16, ANOVA analysis, Tukey's HSD Test). Furthermore, the immunostaining in atypical leiomyomas was more intense in areas with severe atypia compare to less atypical zones. However, there are significant differences in expression of both markers between leiomyomas and atypical leiomyomas (p value <0.0001, Tukey's HSD test) and leiomyomas and leiomyosarcomas (p value <0.0001, Tukey's HSD test).
Conclusions: PTEN and p16 may be used as adjunct diagnostic markers in evaluation of atypia in smooth muscle tumors. Especially in scant specimens like curettage or myomectomy strong positivity for PTEN and p16 may determine the need for follow-up and possible hysterectomy.
Category: Gynecologic & Obstetrics

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 196, Wednesday Afternoon

 

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