Superior vena cava syndrome is caused most commonly by -
Adenocarcinoma
Squamous cell carcinoma
Small cell carcinoma
Large cell carcinoma
"Superior vena cava syndrome results from obstruction of the superior vena cava by central upper lobe tumors, usually the small cell tumors" - Cecil, 5/e, p 1207 (Cecil is a standard text book of Medicine by Saunders publication) "Superior vena cava (SVC) syndrome most frequently occurs with small-cell carcinoma, with bulkly enlargement of involved mediastinal lymph nodes and compression of the SVC." - Schwartz 9/e