Table 3. Immunohistochemical results of CA9 expression in patients with primary OTSCC.

Characteristic	Subtype	No. of cases [%]	CA9 expression		P value
			Low	High
Age (years)	<60	27 [54]	11	16	0.742
	≥60	23 [46]	10	13
Sex	Male	32 [64]	13	19	0.822
	Female	18 [36]	8	10
Differentiation	Well	31 [62]	15	16	0.495
	Moderate	12 [24]	4	8
	Poor	7 [14]	2	5
Pathologic N-stage	N0	39 [78]	18	21	0.262
	N1 + N2	11 [22]	3	8
Pathologic T-stage	T1 + T2	41 [82]	20	21	0.038*
	T3 + T4	9 [18]	1	8
Stage	I + II	30 [60]	16	14	0.047*
	III + IV	20 [40]	5	15

*, P value <0.05. CA9, carbonic anhydrase 9; OTSCC, oral tongue squamous cell carcinoma.