The Use of Progesterone Receptor (PR) and p53 in Assessing Uterine Smooth Muscle Tumors of Uncertain Malignant Potential (STUMP)
John Ross, Shi Wei, Kui Zhang, Michael Conner. University of Alabama at Birmingham, Birmingham, AL
Background: Uterine smooth muscle tumors (USMT) are extremely common, of which the overwhelming majority are benign leiomyomas (BLM) which pose little diagnostic difficulty. Similarly, as leiomyosarcomas (LMS) typically exhibit frankly malignant features including significant nuclear pleomorphism, tumor necrosis and brisk mitotic activity, the diagnosis is usually not overly challenging. However, a small subset of USMT cannot be diagnosed unequivocally as BLM or LMS, thus are classified as smooth muscle tumors of uncertain malignant potential (STUMP). Yet, the diagnosis of STUMP is largely subjective, with no generally accepted criteria. Because of this, attempts to further characterize USMT, specifically STUMP, are warranted. A recent paper by Hewedi, et al showed promise in this regard. The authors used a simple immunohistochemical (IHC) panel (PR and p53) and showed that all LMS show low PR expression and high p53 expression while all non-LMS (STUMP and BLM) stain oppositely (that is, low p53 and high PR).
Design: We sought to assess the usefulness of this panel (p53 and PR) in our cohort of USMT. A total of 27 USMT cases, including 5 BLM, 10 STUMP and 12 LMS, were included. Both were scored on a scale from 0-3 (0=negative, 3=strong, diffuse). We plan to correlate this with clinical follow up data (IRB approved; work in progress).
Results: While PR and p53 did separate many tumors into LMS or non-LMS (BLM/STUMP), this was far from 100%. Based on expected findings (as outlined above - Hewedi, et al), only 17 of 27 tumors behaved exactly as expected.
|Tumor Type||High PR/Low p53||Low PR/High p53||High PR/High p53||Low PR/Low p53|