Multiple pulmonary leiomyomatous hamartoma with secondary ossification

Area of Science:

• Pulmonology
• Oncology
• Pathology

Background:

• A 31-year-old woman with a history of parosteal osteosarcoma presented with multiple pulmonary lesions.
• The nature of these pulmonary lesions, specifically whether they were metastases or a distinct entity, was initially unclear due to the presence of bone formation.

Observation:

• Pulmonary lesions comprised spindle-shaped cells with scattered glandular spaces.
• Some lesions contained bony tissues, raising suspicion for metastatic disease.
• Immunohistochemistry revealed spindle cells, including those near bone, were positive for alpha-smooth muscle actin.

Findings:

• Clonality analysis using the human androgen receptor (HUMARA) gene demonstrated that the pulmonary nodules were polyclonal.
• The polyclonal nature of the lesions ruled out a metastatic origin from the primary parosteal osteosarcoma.
• The findings support that multiple pulmonary leiomyomatous hamartoma (MPLH) can undergo osseous metaplasia.

Implications:

• This case highlights the importance of considering benign conditions like MPLH with secondary ossification in the differential diagnosis of pulmonary nodules in patients with a history of sarcoma.
• It underscores that MPLH can present with osseous metaplasia, a feature that can be mistaken for malignancy.
• Accurate diagnosis relies on a combination of histopathology, immunohistochemistry, and molecular techniques like clonality analysis.