Benign metastasizing leiomyoma

Benign metastasising leiomyoma (BML)leiomyomas is are a rare metastatic phenomenon that is observed when a pelvic leiomyoma is present.

Epidemiology

Women who have undergone hysterectomy for leiomyomas are most commonly affected.

Clinical presentation

Patients are usually asymptomatic at presentation. A history of a hysterectomy for uterine leiomyoma may be indicative. Occasionally symptoms of chest pain, shortness of breath, and cough may be present.

Pathology

The condition is characterized by multiple well-differentiated leiomyomas at sites distant from the uterus. The lesions are histologically identical to their uterine counterparts. It is generally considered that the lesions are a result of haematogenous metastases from benign tumours although some support the hypothesis of multiple independent foci of smooth muscle proliferation.

Location

Although most commonly seen in the lungs ², other sites of involvement include lymph nodes, peritoneum, and retroperitoneal structures.

Associations

• diffuse peritoneal leiomyomatosis
• intravenous leiomyomatosis
• diffuse uterine leiomyomatosis

Radiographic features

Imaging features are often non-specific ³.

When there is lung involvement this may be seen as multiple nodules and pulmonary masses on chest radiography and/or CT. Mediastinal and hilar lymphadenopathy is rare. Cavitation of lesions may occasionally take place and rarely may be accompanied by a pneumothorax. Calcification is rare. Following intravenous contrast, the lesions usually enhance homogeneously ³. Occasional cases have been reported with a miliary pattern or a pattern simulating interstitial lung disease.

Treatment and prognosis

The clinical course is typically indolent and spontaneous resolution has been described.

History and etymology

The condition was first described by P E Steiner in 1939 ⁴.

Differential diagnosis

For lung nodules, there can be a wide differential which includes:

• lung metastases from a malignant tumour
• infectious pulmonary granulomata
• pulmonary sarcoidosis (nodular)
• rheumatoid nodules
• pulmonary amyloidosis