A case of pulmonary benign metastasizing leiomyoma: JAMA
A 38-year-old woman presented with acute abdominal pain. Her history included bariatric gastric bypass surgery (3 years prior), hysterectomy for uterine leiomyomas (5 years prior), and pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension (7 years prior). She had recently undergone ovarian stimulation for in-vitro fertilization.

The patient’s physical examination revealed a tender abdomen without rigidity. Auscultation revealed no abnormal findings. Results of routine blood testing were unremarkable. Imaging studies suggested intussusception at the jejunojejunal anastomosis and a right adnexal mass; the intussusception was successfully reduced laparoscopically.

Multiple ruptured follicles were seen on the surface of the right ovary. A preoperative chest computed tomography scan revealed multiple lung nodules of variable sizes, predominantly in the lower lobes.

The key to the correct diagnosis is the lung biopsy showing a proliferation of fascicles of spindle cells with entrapped benign alveolar tissue without necrosis, atypia, or mitotic activity (Figure 2). The cells were positive for smooth muscle actin, desmin, estrogen, and progesterone receptors.

The findings are consistent with Pulmonary benign metastasizing leiomyoma (PBML).

This patient had no respiratory symptoms, and a decision was made to monitor her. Ovarian stimulation for in-vitro fertilization was considered likely to have caused the growth of already existing microscopic leiomyomatous lesions. Some regression in size was seen in the following months, and the patient remained asymptomatic.

Clinical pearls:-
- Despite its ability to metastasize, this tumor is not locally invasive and requires no treatment with chemotherapy. The biopsy showed no evidence of infection in the nodule, which excludes the diagnosis of septic pulmonary emboli from right-sided endocarditis.

- Sirolimus can stabilize lung function and reduce symptoms in lymphangioleiomyomatosis, which is a slow, progressive, and diffuse growth of smooth muscle cells infiltrating the lung parenchyma. Lymphangioleiomyomatosis manifests radiologically as a diffuse cystic disease as opposed to circumscribed nodules, which are characteristically seen in PBML.

Read more here: https://jamanetwork.com/journals/jama/fullarticle/2708612