Growth patterns of lung metastases from sarcomas

Complete resection of pulmonary metastases from sarcomas is an established method of treatment. While resection margins are well described for primary sarcoma lesions, minimal knowledge is available about margins and factors influencing local tumour control in the lung. The objective of the present study was to describe intrapulmonary patterns of growth for sarcoma metastases as a basis for planning resections. From January 2006 to January 2009, we retrospectively analysed 261 resected pulmonary sarcoma metastases from 52 patients. All metastases were reviewed for histological characteristics and resection margins. Metastases characterised by a solid, well-defined tumour mass were found in 127 of 261 metastases (48.7%). Interstitial spread (39.8%), vascular infiltration (20.7%), satellite nodules (16.1%) and lymphangitic spread (10.7%) were identified as aggressive histological growth characteristics. Forty-five of 52 patients (86.5%) had metastases with a mitotic index of 10 or more per 10 HPF, underlining their high-grade malignant potential. The following characteristics of aggressive intrapulmonary growth were highly correlated with each other: interstitial growth and lymphangitic spread (p = 0.002), interstitial growth and vascular infiltration (p < 0.001), vascular infiltration and satellite nodules (p = 0.009), interstitial growth and pleural invasion (p = 0.004); by contrast, the presence of a fibrous pseudocapsule (17.2%) was not associated with aggressive growth patterns. Almost half of all pulmonary sarcoma metastases could be identified with aggressive patterns of local growth, and only 17.2% are surrounded by a pseudocapsule which might allow safe resection margins.