Lung

• Lung, most common site (BMC Pulm Med 2020;20:292, Case Rep Oncol Med 2014;2014:842801)
• Other reported sites of metastasis include heart, breasts, bone, soft tissue of pelvis, liver, esophagus, lymph nodes, trachea, appendix, central nervous system, skin and scars

• Exact pathophysiology is unclear
• Most accepted hypothesis in the literature is that lesions are clonally derived from uterine leiomyomas (Mod Pathol 2006;19:130, Am J Surg Pathol 2007;31:737)
• Hormonally dependent; there is evidence of disease progression in pregnancy and regression after menopause

• Asymptomatic; incidentally discovered on imaging
• 30% of patients present with symptoms including chest pain, back pain, cough, dyspnea, hemoptysis, pneumothorax and respiratory failure
• Lesions develop months to years after myomectomy; mean duration between hysterectomy and appearance of lung lesions is 23 years (Clin Chest Med 2016;37:589, Ann Thorac Surg 2016;101:253)

• Clinical history of surgical removal of uterine leiomyomas (BMC Pulm Med 2020;20:292, Case Rep Oncol Med 2014;2014:842801)
• Imaging; computed tomography (CT) scan of the thorax
• Microscopic examination of biopsy / excision of pulmonary lesion

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• Prognosis is overall favorable (BMC Pulm Med 2020;20:292, Case Rep Oncol Med 2014;2014:842801)
• Lesions follow an indolent course
• Large tumors may lead to emboli, pulmonary infarction or symptomatic disease

Contributed by Roseann Wu, M.D., M.P.H.

Contributed by Roseann Wu, M.D., M.P.H.

• Generally acellular or paucicellular on fine needle aspiration
• Nonspecific cytologic findings: clusters of uniform, bland, cohesive spindle cells with no mitoses, no necrosis and no significant atypia

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• Actin, desmin, SMA, caldesmon, ER, PR, BCL2 (BMC Pulm Med 2020;20:292, Case Rep Oncol Med 2014;2014:842801)
• Low Ki67

• TTF1, S100, EMA, CK7, CK20, chromogranin, synaptophysin, HMB45, CD10 (BMC Pulm Med 2020;20:292, Case Rep Oncol Med 2014;2014:842801)

• Genetically distinct entity with consistent chromosomal aberrations (19q and 22q terminal deletion in all cases) (Am J Surg Pathol 2007;31:737)
• Similar genetic findings when comparing benign metastasizing leiomyoma and uterine leiomyoma (Mod Pathol 2006;19:130, Hum Pathol 2000;31:126, Int J Gynecol Pathol 2008;27:340, Cancer Genet 2012;205:249, Diagn Mol Pathol 2008;17:145)

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• Lung, left upper lobe, mass, wedge resection:
  • Low grade spindle cell neoplasm, consistent with benign metastasizing leiomyoma (see comment)
  • Comment: Patient’s history of uterine leiomyoma is noted. Immunohistochemical studies were performed with adequate controls on block (A1). The tumor cells are positive for SMA, actin, desmin, ER and PR. The tumor cells are negative for pankeratin, TTF1, HMB45, STAT6 and chromogranin. The morphology and immunohistochemical profile supports the above diagnosis.

• Metastatic low grade leiomyosarcoma (Diagn Mol Pathol 2008;17:145):
  • Atypia, nuclear pleomorphism, necrosis, high mitotic activity favor malignancy
  • miRNA expression differentiates leiomyosarcoma from benign metastasizing leiomyoma
• Solitary fibrous tumor:
  • STAT6 positive, SMA negative, desmin negative
• Schwannoma:
  • S100 positive

A 45 year old woman presents with multiple incidentally discovered, well circumscribed, bilateral lung nodules on CT scan. She is asymptomatic and her history is only notable for a myomectomy, 10 years ago. A biopsy of one of the nodules is performed (see figure above). On immunohistochemical staining, the lesion is negative for STAT6 and the Ki67 proliferative index is low. What is the most likely diagnosis?

1. Benign metastasizing leiomyoma
2. Leiomyosarcoma
3. Pulmonary hamartoma
4. Solitary fibrous tumor

A. Benign metastasizing leiomyoma

Comment Here

Reference: Benign metastasizing leiomyoma

A 45 year old woman presents with multiple incidentally discovered, well circumscribed, bilateral lung nodules on CT scan. She is asymptomatic and her history is only notable for a myomectomy 10 years ago. A biopsy of one of the nodules is performed (see figure above). On immunohistochemical staining, the lesion is negative for STAT6 and the Ki67 proliferative index is low. Based on this specific clinical presentation, what is the best choice for treatment?

1. Chemotherapy
2. Follow up imaging
3. Hormonal therapy
4. Surgical resection

B. Follow up imaging

Comment Here

Reference: Benign metastasizing leiomyoma