spindle cell carcinoma prognosisspindle cell carcinoma survival ratespindle cell neoplasm treatmentspindle cell tumors treatmentspindle cell carcinoma lungsmall cell carcinomaspindle cell melanoma treatmentneuroendocrine small cell carcinomametastatic small cell carcinomasingle cell carcinomasmall cell carcinoma prognosisacinic cell carcinoma treatment