76-year-old white woman was being evaluated in 1998 for left knee replacement surgery because of osteoarthritis. Her past medical history was remarkable for hypertension and a total abdominal hysterectomy for leiomyomas in 1992 and a history of chronic lymphocytic leukemia. A preoperative chest radiograph revealed innumerable bilateral pulmonary nodules that were interpreted as metastases (Figure 1). The woman then underwent a wedge biopsy of the lung. The biopsy specimen consisted of a triangular portion of lung tissue measuring 5.5 x 1.2 X 1.0 cm. Sectioning revealed a multinodular tanwhite lesion measuring 1.3 cm in the maximum dimension. Microscopic examination showed bland, well-differentiated smooth muscle without anaplasia. There was no evidence of necrosis or abnormal mitotic figures (Figures 2 and 3).
What is your diagnosis?
Pathologic Diagnosis: Benign Metastasizing Leiomyoma
Benign metastasizing leiomyoma is a rare entity of
smooth muscle tumors most often described in women with a prior history of uterine fibroids. Fewer than 60 cases of benign metastasizing leiomyoma have been described in the literature. Although a variety of visceral organs can be involved by these lesions, this group of neoplasms has been classically described in women with pulmonary nodules in association with uterine myomas .1,2
The age of individuals most often affected ranges between 36 and 64 years, with a median age of 44 years.3 The disease presentation is variable. Patients generally are asymptomatic, and the disease is discovered by routine radiography. Some patients may have symptoms of mild cough and dyspnea. Radiologically, this entity manifests as multiple pulmonary nodules.
Microscopically, these tumors are composed of well-circumscribed nodules of benign-appearing smooth muscle cells. Cellular atypia, vascular invasion, and mitotic figures are typically absent. These lesions may also contain cysts and epithelial inclusions lined by cuboidal epithelium.
There is some debate in the literature regarding the biological origin of these neoplasms, and many authors suggest that the term benign metastasizing leiomyoma should be abandoned. Many authors believe that this entity represents a group of very well differentiated leiomyosarcomas of low malignant potential, based on the fact that patients with these lesions have actually died from pulmonary insufficiency; furthermore, electron microscopic studies have shown smooth muscle cells with varying degrees of immaturity that is not evident from light microscopic studies. Some investigators believe that the pulmonary process is independent of the presence of uterine smooth muscle tumors because a few women with benign pulmonary smooth muscle tumors have not had uterine tumors. Regardless of the true nature of these neoplasms, clinicians should perform a careful examination in all patients with this diagnosis to rule out a low-grade leiomyosarcoma.
The differential diagnosis includes hamartomas with a prominent smooth muscle component, low-grade leiomyosarcomas, and other spindle cell lesions.
These tumors are described to be hormonally responsive. Due to a limited number of reported cases, clear guidelines for treatment are not available. The prognosis of the disease is variable and seems to depend on the estrogen status of the patient. Current treatment options include hysterectomy, bilateral salpingo-oophorectomy, and long-term hormonal therapy.4 Patients who are asymptomatic with no evidence of disease progression could just be closely observed.
1. Hafiz MA, Wang KP, Berkman A. Fine needle aspiration diagnosis of benign metastasizing leiomyoma of the lung: a case report. Acta Cytol. 1994;38:398402.
2. Winkler TR, Burr LH, Robinson CL. Benign metastasizing leiomyoma. Ann Thorac Surg. 1987;43:100-101.
3. Parenti DJ, Morley TF, Giudice JC. Benign metastasizing leiomyoma: a case report and review of the literature. Respiration. 1992;56:347-350.
4. Banner AS, Carrington CB, Emory WB, et al. Efficacy of oophorectomy in lymphangioleiomyomatosis and benign metastasizing leiomyoma. N EnglJ Med. 1981;305:204-209.
Noman H. Siddiqui, MD; Saba B. Khan, MD; Aliya N. Husain, MD
Accepted for publication June 25, 2002.
From the Department of Pathology, Loyola University Medical Center, Maywood, Ill. Dr Siddiqui is now with the Department of Pathology, University of Illinois Medical Center, Chicago, and Dr Husain is now with the Department of Pathology, University of Chicago Medical Center, Chicago, Ill.
Corresponding author: Noman H. Siddiqui, MD, Department of Pathology, University of Illinois, 1740 W Taylor St, Room 3118 A, Chicago, IL 60612 (e-mail: noman*uic.edu).
Reprints not available from the authors.
Copyright College of American Pathologists Apr 2003
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