Benign Metastasizing Leiomyoma of the Lung: Potential Role of Low-Grade Malignancy

Pulmonary and mediastinum metastasis of uterine leiomyoma: A case report

RATIONALE

Pulmonary benign metastasizing leiomyoma (PBML) is rare, usually occurs in women who underwent hysterectomy during the reproductive years, and has no obvious clinical symptoms. A full understanding of the characteristics of PBML is important for its sequential treatment and prognosis.

PATIENT CONCERNS

In this report, a 36-year-old female patient with previous uterine leiomyoma who underwent 3 surgical resections of the uterus, bilateral fallopian tubes, and partial omentum was investigated. The physical examination revealed a tumor in the right lower lobe and mediastinum and a solid nodule in the right middle lobe.

DIAGNOSES

Chest computed tomography (CT) confirmed a tumor in the right lower lobe and mediastinum and a solid nodule in the right middle lobe. Further positron-emission tomography computed tomography (PET-CT) with 18F-fluorodeoxyglucose (FDG) of the whole body showed mildly intense accumulation of 18F-FDG in the tumor (maximum standardized uptake value [SUV max], 2.6). A pathological examination then confirmed the presence of fibrous and vascular tissue after CT-guided percutaneous biopsy of the tumor in the right lower lobe. Additionally, surgical resection of the tumor and nodule was performed for histological analysis and immunohistochemical assays for estrogen receptor (ER) and progesterone receptor (PR).

INTERVENTIONS

The patient underwent complete tumor surgical resection and nodule wedge resection.

OUTCOMES

No postoperative complications occurred. No recurrence or other signs of metastasis were found during an 18-month follow-up observation period.

CONCLUSION

In this case, lung and mediastinal metastasis of uterine fibroids was observed. However, depending on only a postoperative histological analysis is insufficient for the diagnosis of PBML. Histological analysis combined with an evaluation of the expression levels of ER and PR is crucial for the diagnosis and treatment of PBML.

Deep sequencing reveals the molecular pathology characteristics between primary uterine leiomyoma and pulmonary benign metastasizing leiomyoma

PURPOSE

Pulmonary benign metastasizing leiomyoma (PBML), a rare condition of smooth muscle tumor, originates from women with a history of uterine leiomyoma (LM). Numerous genetic studies of uterine LM have been reported; however, there are few cytogenetic and molecular descriptions of PBML. Therefore, molecular subtyping is necessary to understand the pathogenesis of metastasizing sites.

METHODS

Driver gene exon-capture sequencing was performed on one patient's peripheral blood, paraffin samples from primary uterine LM, and lung metastasizing leiomyoma 8 years later.

RESULTS

The results showed that the same missense mutations of BLMH, LRP2, MED12, SMAD2, and UGT1A8 were concurrently mutated in the primary uterine LM and the PBML. Moreover, a splice mutation of PTEN (c.492+1G>A) was uniquely identified in the lung metastasis of the patient.

CONCLUSION

This study indicates that the metastatic lung lesions were derived from the same malignant cell clone of uterine LMs and later acquired the novel driver mutations in the evolution of the tumor. In addition, driver gene sequencing can discriminate somatic driver mutations as biological indicators of potential malignant leiomyoma and can identify pathogenic variation driver mutations, which could be used for individualized therapy.

Benign Metastasizing Leiomyoma

Benign metastasizing leiomyoma (BML) is a rare and poorly characterized disease affecting primarily premenopausal women. Asymptomatic patients are often diagnosed incidentally by radiographs or other lung-imaging procedures performed for other indications, and the diagnosis is eventually confirmed by biopsy. Patients with BML are usually treated pharmacologically with antiestrogen therapies or surgically with oophorectomy or hysterectomy. Antiestrogen therapy is typically efficacious and, in general, most patients have a favorable prognosis. Asymptomatic patients with a confirmed diagnosis of BML, may be followed conservatively without treatment.

Benign metastatic leiomyoma presenting as a hemothorax

Uterine leiomyomas have been reported to metastasize to various organs including the lungs, skeletal muscles, bone marrow, peritoneum, and heart. They may present with symptoms related to the metastases several years after hysterectomy. These tumors regress after menopause, and it is rare to detect active tumors in postmenopausal women. Despite their ability to metastasize, they are considered to be benign due to the lack of anaplasia. Pulmonary benign metastasizing leiomyoma is usually detected in the form of pulmonary nodules incidentally on imaging. Tissue biopsy of these nodules is required to identify them as benign metastasizing leiomyomas. Immunohistochemical analysis and molecular profiling may further help detect any malignant transformation in it. Untreated pulmonary benign metastasizing leiomyoma may result in the formation of cystic structures, destruction of lung parenchyma, and hemothorax and may cause respiratory failure. Surgical resection and hormonal therapy help prevent progression of this disease and provide an avenue for a cure.