Leiomyoma with Bizarre Nuclei: A Current Update

Abstract

Leiomyoma with bizarre nuclei (LBN), also known as symplastic leiomyoma, is a histological subtype of benign leiomyoma with bizarre cells and nuclear atypia. Differentiating LBN from other benign leiomyoma subtypes, uterine smooth muscle tumors of uncertain malignant potential (STUMP), or leiomyosarcoma (LMS) can be diagnostically challenging owing to overlapping features in clinical presentation and pathologic morphological analysis. The difficulty of distinguishing LBN from other lesions, especially from LMS, and the potential of LBN for subsequent malignant transformation make LBN an important topic of research. Herein, we review the definition, diagnosis, treatment, and prognosis of LBN. Histopathological examination is essential for distinguishing LBN from other diseases. Pathology sampling and morphological examination remain the key to diagnosis. The newly established ancillary immunohistochemical (IHC) and molecular genetic analysis can be useful tools for differential diagnosis. Furthermore, serum biomarkers and imaging examination may also be useful diagnostic tools. Attention should be paid to the differentiation between LBN and LMS because morphological diagnosis may still be challenging in some cases. Some IHC markers of LBN have been identified, which may be helpful for differential diagnosis. Furthermore, the use of IHC panels as diagnostic markers may be advocated. Molecular genetic studies suggest that some genes can aid with the differential diagnosis between LBN and LMS. However, increasing evidence support the idea that LBN and LMS are molecularly related, indicating that LBN may represent a potentially malignant stage of precancerous progression. At present, conservative treatment is recommended for primary LBN, especially for patients desiring to retain fertility, but close follow-up with imaging examinations is required.

Uterine leiomyoma with bizarre nuclei – A series of four cases

“…Leiomyoma is the most common benign neoplasm of the uterus, occurring predominantly in the reproductive age group. 1,2 As per previous studies, the growth of leiomyoma depends up on estrogen and progesterone, 2 role of phosphorylation of proteins for the growth of leiomyoma was suggested by Ura et al 3 A wide range of morphological variants and secondary changes are seen in leiomyoma. 1 Leiomyoma with bizarre nuclei (LBN) is an uncommon variant of leiomyoma.…”

“…1 Leiomyoma with bizarre nuclei (LBN) is an uncommon variant of leiomyoma. 2 This lesion was first reported in 1909 by Kelly and Cullen, they named it "sarcomatous degeneration" later some authors used terms such as "degenerative cytologic change," "symplastic cells," and "leiomyosarcoma in situ". 4 The terminology 'bizarre leiomyoma" was used by Christopherson et al in 1972.…”

“…4 The terminology 'bizarre leiomyoma" was used by Christopherson et al in 1972. 2 In 1994, it was termed atypical leiomyoma and as per Bell's criteria it has moderate to marked nuclear atypia, mitosis <10/ high power fields (HPF) and no tumor cell necrosis. 5 Previous studies have used the following terminology such as atypical leiomyoma with low risk of recurrence, atypical leiomyoma, symplastic leiomyoma, and pleomorphic leiomyoma.…”

“…As per 2020 WHO classification LBN is a subtype of leiomyoma with bizarre cells in a multifocal to diffuse distribution with a background of conventional leiomyoma. 2 The mitotic count in LBN is <5 mitoses/ 10 HPF of 0.55-mm diameter and 0.24-mm 2 area and LBN with 5-9 mitoses/10 HPF should be considered in the category of smooth muscle tumors of uncertain malignant potential (STUMP). 2…”

“…2 The mitotic count in LBN is <5 mitoses/ 10 HPF of 0.55-mm diameter and 0.24-mm 2 area and LBN with 5-9 mitoses/10 HPF should be considered in the category of smooth muscle tumors of uncertain malignant potential (STUMP). 2…”