DISCUSSION
RCC is the sixth most common malignant tumor in males and the tenth most common malignant tumor in females[10]. RCC recurs after more than 10 years of nephrectomy in 10% of the cases[11]. The most common sites of metastasis include lungs, bones, lymph nodes, adrenal glands, liver, brain contralateral kidney, and pancreas[5]. Metastatic clear cell RCC has a poor prognosis with a median overall survival of 12 months only which has improved in the last decade[12]. Pulmonary metastasis from RCC after a long interval is rare. This is the first case of lung metastasis from renal cell carcinoma that we have encountered in our institution. To our knowledge, this is the first case of lung metastasis secondary to clear cell renal cell carcinoma reported from Nepal to date.
Shiono et al. reported a case with repeated metastasectomy for lung metastasis 16, 24, and 25 years after RCC treatment[7]. Shiono et al. also reported a mini-review of 5 cases of RCC with lung metastasis after 20-28 years of resection of primary neoplasm throughout 1973-1998[7]. Watanabe et al. reported pulmonary metastasectomy after 10 years of nephrectomy. Left upper lobectomy was performed in an 82-year-old patient who was consequently disease-free at 9 months follow-up[8]. Tamburrini et al. reported lung metastasis after 37 years of RCC resection. The patient had a central hilar mass which was suspected as primary lung cancer but histological examination revealed metastatic RCC. Left pneumonectomy was performed in this patient. The patient was recurrence-free at 3 years follow-up[9]. Genand et al. reported solitary lung metastasis in a patient 17 years after nephrectomy for RCC[13].
Disease recurrence likelihood for RCC depends on several known and unknown factors including host and tumor factors[5]. Prognostic indicators for RCC include complete resection of all metastasis, low number of metastasis, long disease-free interval between primary tumor diagnosis and lung lesions, lymph node involvement, and size of pulmonary nodule[9]. Host immune response has been hypothesized to play a role to determine the time for the presentation of RCC metastasis. Duration decreases with compromised immune response[9]. The five and 10-year overall survival rate following pulmonary metastasectomy for metastatic renal cancer was 83% and 41.7% respectively according to Chen et al. [14]and 75% and 59% respectively according to Meacciet al.[15].