Oncofetal protein IMP3: a useful diagnostic biomarker for leiomyosarcoma Human Pathology, 04/13/2012

Cornejo K et al. – The expression of IMP3 in both uterine and soft tissue leiomyosarcomas can be used as a positive biomarker to increase the level of confidence in establishing a definitive diagnosis of a malignant smooth muscle tumor.

• A total of 216 cases (resection, n = 183; biopsy, n = 33) consisting of 82 leiomyosarcomas (uterine, n = 15; soft tissue, n = 67), 62 leiomyomas (uterine, n = 50; soft tissue, n = 12), and 72 uterine-variant leiomyomas (atypical, n = 19 [14%]; cellular, n = 21 [16%]; mitotically active, n = 12 [9%]; myxoid, n = 11 [8%]; vascular, n = 3 [2%]; epithelioid, n = 1 [1%]; benign metastasizing, n = 1 [1%]; and smooth muscle tumors of uncertain malignant potential, n = 4) were examined by immunohistochemistry for IMP3 expression.

• IMP3 showed strong cytoplasmic staining in 43 (52%) of 82 leiomyosarcomas, regardless of histologic grades.
• There was no difference in IMP3 expression between uterine and soft tissue leiomyosarcomas.
• In contrast to malignant tumors, IMP3 expression was not found in any of the typical leiomyomas (0/62 cases).
• All uterine-variant leiomyomas were negative, except for 3 cases (atypical variant, n = 2; cellular variant, n = 1) for IMP3 staining.