Cystic duct cancer: Should it be deemed as a type of gallbladder cancer?

Table 1 Comparison of clinical characteristics between cystic duct cancer, gallbladder cancer and extrahepatic cholangiocarcinoma, n (%)

Variable	No. (%) of patients			P value
	GC (n = 4878)	EC (n = 3295)	CC (n = 36)	CC vs GC	CC vs EC
Sex				< 0.001a	0.067
Male	1528 (31.3)	1880 (57.1)	26 (72.2)
Female	3350 (68.7)	1415 (42.9)	10 (27.8)
Age at diagnosis (median)	71	69	66.5	0.059	0.161
Year of diagnosis				0.487	0.492
2006 to 2010	2041 (41.8)	1377 (41.8)	13 (36.1)
2011 to 2015	2837 (58.2)	1918 (58.2)	23 (63.9)
Marital status				0.269	0.948
Not married	2348 (48.1)	1264 (38.4)	14 (38.9)
Married	2530 (51.9)	2031 (61.6)	22 (61.1)
Race				0.703	0.330
White	3604 (73.9)	2529 (76.8)	25 (69.4)
Black	683 (14.0)	246 (7.5)	5 (13.9)
Others	591 (12.1)	520 (15.8)	6 (16.7)
Tumor size (median)	33	25	25.5	0.005a	0.195
SEER historical stage				< 0.001a	0.326
Localized	1934 (39.6)	522 (15.8)	3 (8.3)
Regional	1150 (23.6)	2098 (63.7)	27 (75.0)
Distant	1794 (36.8)	675 (20.5)	6 (16.7)
Surgical procedure				< 0.001a	0.047a
No operation	1014 (20.8)	1468 (44.6)	8 (22.2)
Biopsy/partial resection	833 (17.1)	535 (16.2)	10 (27.8)
Total resection	2490 (51.0)	417 (12.7)	6 (16.7)
Radical resection	541 (11.1)	875 (26.6)	12 (33.3)
Region				0.928	0.865
Alaska	10 (0.2)	6 (0.2)	0 (0.0)
East	1705 (35.0)	1104 (33.5)	14 (38.9)
Northern plains	441 (9.0)	301 (9.1)	5 (13.9)
Pacific coast	1858 (51.1)	1346 (41.9)	16 (44.4)
Southwest	149 (4.1)	86 (3.4)	1 (2.8)
Histology				0.042a	0.725
Adenocarcinoma	4152 (85.1)	3086(93.7)	35 (97.2)
Others	726 (14.9)	209 (6.3)	1 (2.8)

CC: Cystic duct cancer; GC: Gallbladder cancer; EC: Extrahepatic cholangiocarcinoma; SEER: Surveillance, Epidemiology, and End Results.

^aP < 0.05.