대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Benign metastasizing leiomyoma

Radiologic Findings

Fig 1. Chest PA shows round mass in left hilum.
Fig 2-4. CT scans reveals an 3.1cm, lobulating nodule in left upper lobe. This mass shows heterogeneous density with poor enhancement (average HU 33).
Fig 5. This lesion shows no FDG uptake in PET-CT scan

Brief Review

Benign metastsizing leiomyoma (BML) is characterized by the presence of benign-appearing smooth muscle tumors located outside the uterus, commonly in the lungs. These tumors have low mitotic activity and lack invasive characteristics, distinguishing them from malignant counterparts like leiomyosarcoma. BML typically occurs in women of reproductive age and often follows a history of uterine leiomyomas.

Pathogenesis
- Lymphatic and Hematological Spread: Evidence suggests that BML may arise from the spread of smooth muscle cells through lymphatic or blood vessels.
- Coelomic Metaplasia: Similar to endometriosis, BML may develop from metaplastic transformation of coelomic epithelium or peritoneal seeding.
- Hormonal Influence: The presence of estrogen and progesterone receptors in BML indicates that hormonal factors may play a significant role in tumor growth, as seen in endometriosis.

Diagnostic Considerations
Differentiating BML from leiomyosarcoma is crucial due to the latter's aggressive nature. The careful pathological assessment is crucial to exclude malignancy when diagnosing BML.

Chest CT finding
Multiple pulmonary nodules: BML commonly manifests as multiple, well-circumscribed nodules in both lungs. The pulmonary nodules can range in size, but are usually small to moderate in diameter. These nodules typically demonstrate slow or no growth over time, consistent with their benign nature. Unlike malignant lesions, BML nodules do not show invasive features or destruction of surrounding lung tissue. The nodules are usually solid and do not exhibit cavitation or calcification.
It's important to note that while these findings are characteristic of BML, they are not entirely specific. The diagnosis of BML requires correlation with clinical history, particularly a history of uterine leiomyomas, and often necessitates biopsy for definitive diagnosis.
Our patient shows a single lung nodule, not multiple, on the chest CT. No FDG uptake on the PET-CT suggests the benign nature of this nodule. She underwent a laparoscopic myomectomy for uterine myoma 3 years ago.

Clinical Implications
The understanding the pathogenesis of BML could improve treatment approaches. Hormonal therapies have shown efficacy in managing symptoms and potentially reducing tumor size, aligning with findings in endometriosis.

References

1. Pacheco-Rodriguez, Gustavo, Angelo M. Taveira-DaSilva, and Joel Moss. "Benign metastasizing leiomyoma." Clinics in chest medicine 37.3 (2016): 589-595.
2. Awonuga, Awoniyi O., et al. "Pathogenesis of benign metastasizing leiomyoma: a review." Obstetrical & gynecological survey 65.3 (2010): 189-195.
3. Barnaś, Edyta, et al. "Benign metastasizing leiomyoma: a review of current literature in respect to the time and type of previous gynecological surgery." PLoS One 12.4 (2017): e0175875.

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