A 43-year-old woman, Gravida 3, Para 3, complained of severe lower abdominal pain, mostly in the left hypochondrium, for six months. The patient's medical and gynecological history was unremarkable, except a myomectomy for a benign leiomyoma performed 12 years ago. The physical examination revealed a bloated abdomen, a palpable left hypochondrium mass, and an enlarged uterus. These findings suggested leiomyoma or adenomyosis. The abdomen ultrasound revealed multiple large and heterogenous uterine nodules, the largest measuring 7 cm. Size and appearance were normal for both ovaries. The left hypochondrium contained a 10 cm mass of uncertain origin featuring multiple hypoechoic regions, indicating necrosis. The abdominal CT scan indicated multiple uterine fibroids, a left hypochondrium tumor, and retroperitoneal lymphadenopathies in the left external iliac and lateral aortic chains. The chest CT showed numerous pulmonary nodules in both lungs. MRI showed an enlarged asymmetrical myomatous uterus. T2-weighted fast SEMR images showed a normal endometrial stripe and junctional zone with multiple well-circumscribed intramural and subserosal leiomyomas, consistent with type 5 and 6 lesions, according to the International Federation of Gynecology and Obstetrics leiomyoma subclassification system. Leiomyomas showed moderate signal intensity compared to the uterine wall with no necrosis or bleeding. MRI also revealed a 10 cm tumor of undefined origin in the left hypochondrium with retroperitoneal lymphadenopathies of the left external iliac and lateral aortic chains. An axial T1-weighted MR scan showed fibroids with high contrast enhancement and no non-enhancing areas. The bridging vessels sign indicated the uterine origin of masses. Since these imaging results were inconclusive and alarming for metastatic uterine sarcoma or digestive malignancy, we performed a diagnostic and interventional laparotomy in collaboration with the digestive surgery team. The intraoperative findings included: 1) subsural and intramural masses with macroscopic uterine fibroids; 2) normal ovaries and tubes; 3) a polylobed solid mass friable in some areas and adhering only to the visceral peritoneum in the left hypochondrium; and 4) lymphadenopathy in the left external iliac and lateral aortic chain, indicating metastases. As a result, we underwent interannexial hysterectomy, total left hypochondrium mass removal, and lymph node dissection. Anatomopathological examination of the uterine masses revealed benign proliferation of smooth muscle cells, suggestive of a leiomyoma. The cell nuclei were hyperchromatic and elongated, and lacked signs of atypia or abnormal mitotic processes. The smooth muscle cells had a fascicular organization, separated by a well-vascularized fibro-hyalin stroma without any necrotic zones. The cellularity of the left hypochondrium mass resembled that of uterine leiomyoma. There was no necrosis or hemorrhage, and it was composed of fascicular smooth muscle cells. Lymph nodes removed from the left external iliac and lateral aortic chains revealed massive metastasis of smooth muscular tissue that nearly totally replaced the usual lymphatic tissue with only a few lymph nodes retaining the usual structure. This lymph node smooth muscle tissue resembled uterine leiomyoma and left hypochondriac tumor. The lymph nodes, left hypochondriac tumor, and uterine leiomyoma were immunohistochemically analyzed. All tissues tested were positive for h-caldesmon, smooth muscle actin (SMA), estrogen (ER), and progesterone receptors (PR). Importantly, a major finding was made during the immunohistochemical examination of the peritoneal mass and one of the resected lymph nodes, which revealed coelomic tissue adjacent to the muscle proliferation within these metastatic sites. This tissue is composed of a columnar coelomic epithelium resting on a moderately cellular mesenchymal tissue. The surrounding muscle proliferation was highly positive for smooth muscle actin and h-caldesmon, while the coelomic tissue was negative. Both the coelomic tissue and muscle foci of the iliac lymph node demonstrated diffuse robust and homogenous estrogen and progesterone receptor positivity. Based on the clinical presentation, imaging studies, histology, immunohistochemical positive stains, and Ki-67 index less than 1%, we retained the diagnosis of BML involving the lungs, abdomen, and retroperitoneal lymph nodes and decided to monitor the patient without hormonal therapy.