Molecular-Based Immunohistochemical Algorithm for Uterine Leiomyosarcoma Diagnosis

The morphologic assessment of uterine leiomyosarcoma (LMS) may be challenging, and diagnostic immunohistochemical (IHC) analysis is currently lacking. We evaluated the genomic landscape of 167 uterine LMS by targeted next-generation sequencing (NGS) to identify common genomic alterations. IHC analyses corresponding to these genomic landmarks were applied to a test cohort of 16 uterine LMS, 6 smooth muscle tumors of uncertain malignant potential (STUMP), and 6 leiomyomas with NGS data and a validation cohort of 8 uterine LMS, 12 STUMP, 21 leiomyomas and leiomyoma variants, 7 low-grade endometrial stromal sarcomas, and 2 diagnostically challenging uterine smooth muscle tumors. IHC results were individually interpreted by 3 pathologists blinded to NGS data. Overall, 94% of LMS showed ≥1 genomic alteration involving TP53, RB1, ATRX, PTEN, CDKN2A, or MDM2, with 80% showing alterations in ≥2 of these genes. In the test cohort, an initial panel of p53, Rb, PTEN, and ATRX was applied, followed by a panel of DAXX, MTAP, and MDM2 in cases without abnormalities. Abnormal p53, Rb, PTEN, and ATRX IHC expression was seen in 75%, 88%, 44%, and 38% of LMS, respectively, in the test cohort. Two or more abnormal IHC results among these markers were seen in 81% of LMS. STUMPs demonstrated only 1 IHC abnormality involving these markers. No IHC abnormalities were seen in leiomyomas. In the validation cohort, abnormal p53, Rb, and PTEN IHC results were seen in LMS, whereas rare STUMP or leiomyomas with bizarre nuclei showed IHC abnormalities involving only 1 of the markers. Abnormalities in ≥2 markers were present in both diagnostically challenging smooth muscle tumors, confirming LMS. Concordance was excellent among pathologists in the interpretation of IHC (κ = 0.97) and between IHC and NGS results (κ = 0.941). Uterine LMS exhibit genomic landmark alterations for which IHC surrogates exist, and a diagnostic algorithm involving molecular-based IHC may aid in the evaluation of unusual uterine smooth muscle tumors.

Uterine smooth muscle tumors of uncertain malignant potential (STUMP): A retrospective study in a single center

OBJECTIVE

Uterine smooth muscle tumors of uncertain malignant potential (STUMP) is a heterogeneous group of tumors with histological and biological diversity that cannot be defined as a benign leiomyoma or malignant leiomyosarcoma. The study aims to investigate the diagnostic methods, treatment management and prognosis of STUMP patients in a 13-year period.

STUDY DESIGN

We retrospectively reviewed the clinicopathologic information of 31 STUMP patients in Peking University People's Hospital. Statistical analyses were conducted to compare the difference of clinical characteristics between the women in myomectomy group and those in hysterectomy group.

RESULTS

The most common clinical presentation was menstrual disorder. The tumors were mainly manifested as hypoechoic, non-cystic nodules with low blood flow signal by pelvic doppler ultrasonography. Most tumors carried Ki-67 index ranging from 10% to 30%. Immunohistochemical markers such as ER, PR, p16 and Desmin was positively expressed in tumors. At the first operation, 21 cases underwent myomectomy and 10 cases underwent hysterectomy. The patients in myomectomy group were younger than those in hysterectomy group. In the follow-up period, two cases experienced a relapse in the form of STUMP within 36 months. One case died of cardiovascular accident while the other cases were alive. Six of 21 women in myomectomy group desired pregnancy and two healthy live births were recorded.

CONCLUSION

The diagnosis of STUMP primarily depends on histopathologic features. Fertility-sparing surgery may be a treatment selection for patients with fertility desire. Patients with STUMP, especially in the case of myomectomy, should be informed of recurrence risk and monitored closely.

MED12 exon 2 mutation is uncommon in intravenous leiomyomatosis: clinicopathologic features and molecular study

Intravenous leiomyomatosis (IVL) is a rare neoplasm that is characterized by smooth muscle cell proliferation within venous vessels. The aim of this study is to investigate the clinicopathological features, immunophenotypes, and MED12 gene mutations in IVL. Nine cases of IVL from the Affiliated Hospital of Qingdao University were collected, and the clinicopathological features were reviewed. The immunohistochemical expressions of p16, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), alpha thalassemia/mental retardation syndrome X-linked (ATRX), retinoblastoma 1 (RB1), fumarate hydratase (FH), and p53, were evaluated. The mutation status of MED12 gene exon 2 was detected by Sanger sequencing. All the 9 patients were women ranging from 32 to 58 years, and uterine leiomyomas were identified in 5 patients. Immunohistochemical staining showed that all IVL and leiomyoma samples were positive for estrogen receptor and progesterone receptor, but negative for CD34. IVL displayed similar immunostaining patterns with their uterine counterparts with focal p16 immunostaining. FH, PTEN, ATRX, and RB1 were variably positive, and p53 and Ki-67 positive rates were less than 5% in all cases. Two novel genetic variations at MED12 exon 2, a synonymous mutation c.141C>T (p.Asn47=), and an in-frame deletion mutation c.133_147del15 (p.Phe45_Pro49del) were identified in two IVL cases. One missense mutation c.131G>A (p.Gly44Asp) was identified in one uterine leiomyoma. The remaining 11 tumor samples (7 IVL cases and 4 uterine leiomyomas) showed no mutations at MED12 exon 2. Our results showed two novel MED12 mutations in IVL. The MED12 mutations are different between IVL and uterine leiomyoma. These findings indicate that IVL is a unique entity and different from uterine leiomyoma.