Can transrectal ultrasonography distinguish anorectal malignant melanoma from low rectal adenocarcinoma? A retrospective paired study for ten years

Table 1 TRUS features of ARMM and LRAC

Features	ARMM (n = 9)	LRAC (n = 27)	P
L (mean ± SD, mm)	28.22 ± 12.29	40.22 ± 15.16	0.037
T (mean ± SD, mm)	14.63 ± 6.73	15.75 ± 7.33	0.699
M-Dist (mean ± SD, mm)	50.78 ± 11.70	63.81 ± 18.73	0.028
I-Dist (mean ± SD, mm)	36.67 ± 8.82	43.44 ± 19.60	0.181
DOI n (%)			0.046
Shallow	6(66.67)	7 (25.93)
Deep	3(33.33)	20 (74.07)
PSV (cm/s)	31.40 ± 25.56	34.3 ± 22.91	0.547
RI	0.77 ± 0.14	0.83 ± 0.13	0.416
Location n (%)			0.255
A	6(66.67)	11(40.74)
NA	3(33.33)	16 (59.26)
Echotexture, n (%)			0.148
Homogeneous	7(77.78)	26(96.30)
Heterogeneous	2 (22.22)	1(3.70)
LN metastasis, n (%)	4(44.44)	16(59.26)	0.470
Maximum diameter of LN (mm)	10.25 ± 6.80	6.25 ± 1.75	0.384

TRUS: Transrectal ultrasonography. ARMM: Anorectal malignant melanoma. LRAC: Low rectal adenocarcinoma. L: length. T: Thickness. M-Distance: the distance between the tumor midpoint and the anal verge. I-Distance: the distance between the inferior border of tumor and the anal verge. DOI: depth of invasion. Shallow: mucosa-submucosa invasion. Deep: muscularis propria-adventitia invasion. LN metastasis: the presence of lymph node metastasis. Maximum diameter of LN: the maximum diameter of metastatic lymph node. SD: Standard deviation. Bold indicates statistical significance