Lymphadenectomy in pulmonary metastasectomy

Abstract

Lymph node (LN) removal during pulmonary metastasectomy is a prerequisite to achieve complete resection or at least collect prognostic information, but is not yet generally accepted. On average, the rate of unexpected lymph node involvement (LNI) is less than 10% in sarcoma, 20% in colorectal cancer (CRC) and 30% in renal cell carcinoma (RCC) when radical LN dissection is performed. LNI is a negative prognostic factor and presence of preoperative mediastinal disease usually leads to exclusion of the patient from metastasis surgery. Nonetheless, some authors found excellent prognoses even with mediastinal LNI in colorectal and RCC metastases when radical LN dissection was performed (median survival of 37 and 36 months, respectively). Multiple metastases, central location of the lesion followed by anatomical resections are associated with a higher LNI rate. The real prognostic influence of systematic LN dissection remains unclear. Two positive effects were described after radical lymphadenectomy: a trend for improved survival in RCC patients and a reduction of mediastinal recurrences from 23% to 0% in CRC patients. Unfortunately, there is a great number of studies that do not demonstrate any positive effect of lymphadenectomy during pulmonary metastasectomy except a pseudo stage migration effect. Future studies should not only focus on survival, but also on local and LN recurrence.

Keywords: Pulmonary metastasectomy; lymph node dissection; lymph node sampling.

Figure 1

H&E stained histologic sections of a rectum cancer lung metastasis demonstrating lymph vessel involvement. (A) 4× magnification of the main metastasis (arrow 1) and a chain of tumor tissue in lymphatic vessels surrounding a small pulmonary artery branch (arrow 2). (B) 10× magnification demonstrating tumor tissue inside small lymph vessels (arrows) along a larger pulmonary artery branch.

Figure 2

CT scan of an isolated CRC lung metastases in the left lower lobe with interlobar attachment to the upper lobe. Lower lobe resection with LAD revealed a 5.2 cm adenocarcinoma of colorectal origin with L1 and V1 and intrapulmonary and hilar LNI. CRC, colorectal cancer; LAD, lymphadenectomy; LNI, lymph node involvement.