Growth patterns of lung metastases from sarcoma: prognostic and surgical implications from histology

Pulmonary metastasectomy is firmly established in the multidisciplinary management of patients with advanced sarcomas. While the number of metastases, completeness of resection, disease-free interval and grading of the primary sarcoma are well established prognostic factors in metastatic surgery, histological parameters are not widely evaluated. The objective of the present study was to evaluate the prognostic impact of intrapulmonary growth patterns of sarcoma metastases.

We retrospectively analysed the clinicopathological characteristics of 52 sarcoma patients who underwent surgical resection of lung metastases at our centre from January 2006 to January 2009. The histological growth characteristics of all 261 metastases have been categorized and published previously. 'Interstitial growth' was defined as a diffuse spread of the sarcoma cells into the alveolar septae at the transition of the metastasis to the normal lung tissue and was found to be prognostic. 'Pleural penetration' was defined as the infiltration and destruction of all visceral pleural layers by the tumour and was found to be a risk factor for local recurrence.

The median post-metastasectomy overall survival was 50.3 months, and the corresponding 5-year survival rate was 44.7%. Age >55 years at metastasectomy (P = 0.02), the presence of interstitial growth (P = 0.008), size of the largest metastasis >35 mm (P = 0.023) and the presence of tumour recurrence at any site after metastasectomy (P < 0.001) were identified as risk factors for death. Pleural penetration (P = 0.007) and size of the metastasis >5 mm were found to be risk factors for local intrapulmonary recurrence.

Interstitial tumour growth, which is easily detected by light microscopy, can serve as a strong predictor of survival following pulmonary metastasectomy in sarcoma patients. Obvious pleural infiltration indicates the need for larger margins.