Melanoma metastases in the abdomen and pelvis: Frequency and patterns of spread

Table 1 Distribution of primary melanoma among all patients scanned (n = 508) n (%)

Primary tumor location	Cases
Back	114 (22.4)
Lower extremity	103 (20.3)
Head/neck	88 (17.3)
Ocular	72 (14.2)
Anterior chest wall	33 (6.5)
Upper extremity	29 (5.7)
Pelvis	15 (3.0)
Anorectal	13 (2.6)
Sinonasal	10 (2.0)
Anterior abdominal wall	8 (1.6)
Labia/vagina	4 (0.8)
Oral mucosa	3 (0.6)
Enteric	1 (0.2)
Unknown	15 (3.0)

Table 2 Distribution of melanoma metastases among patients with identifiable metastases by computed tomography

Location of metastasis	Number of cases	% of cases (n = 508)	% of cases with metastases (n = 181)
Liver	85	16.7%	47.0%
Pelvic nodes	48	9.4%	26.5%
Adrenal	28	5.5%	15.5%
Subcutaneous implants	27	5.3%	14.9%
Spleen	22	4.3%	12.2%
Retroperitoneal nodes	20	3.9%	11.0%
Intraperitoneal nodes	18	3.5%	9.9%
Mesenteric/peritoneal implants	18	3.5%	9.9%
Bone	11	2.2%	6.1%
Kidney	10	2.0%	5.5%
Small bowel	10	2.0%	5.5%
Retroperitoneal implants	7	1.4%	3.9%
Pancreas	3	0.6%	1.7%
Gastric	2	0.4%	1.1%
Large bowel	1	0.2%	0.6%
Ovary	1	0.2%	0.6%
Appendicular skeletal muscle	1	0.2%	0.6%
Diaphragm	1	0.2%	0.6%

Table 3 Rate of metastases by primary location and common location of metastases by location of primary tumor

Location of primary tumor	Cases with metastases		Most common sites of metastatic disease
	n	%
Lower extremity	54/103	52.4%	Pelvic lymph node 53.7%	Liver 29.6%	Retroperitoneal lymph node 20%
Back	40/114	35.1%	Liver 45%	Adrenal 25%	Spleen 22.5%
Head/neck	24/88	27.3%	Liver 62.5%
Ocular	20/72	27.8%	Liver 70%	Abdominal lymph node 15%
Anterior chest wall	12/33	36.4%	Liver 41.7%	Adrenal 16.7%	Pelvic lymph node 16.7%
Upper extremity	8/29	27.6%	1	1	1
Pelvis	5/15	33.3%	1	1	1
Anorectal	3/13	23.1%	1	1	1
Sinonasal	3/10	30%	1	1	1
Anterior abdominal wall	1/8	12.5%	1	1	1
Labia/vagina	1/4	25%	1	1	1
Oral mucosa	0/3	0%	1	1	1
Enteric	0/1	0%	1	1	1
Unknown	10/15	66.7%	1	1	1

¹Distribution of metastases not detailed due to low number of primary tumors at these locations which would be expected to substantially skew the data.

Table 4 Location of atypical metastases in patients with only atypical metastases (n = 21) n (%)

Location of atypical metastases
Subcutaneous implant	9 (42.90)
Enteric	5 (23.80)
Small bowel	3 (14.30)
Large bowel	1 (4.80)
Gastric	1 (4.80)
Spleen	4 (19.00)
Peritoneal implant	1 (4.80)
Kidney	1 (4.80)
Multiple sites (subcutaneous, mesenteric, retroperitoneal, diaphragm)	1 (4.80)

Table 5 Overall frequency of atypical metastases and rate of atypical metastases based on primary location

Primary site	Cases with atypical metastases n (% of cases with metastases)	Cases with only atypical mets
		n	% of cases of that primary	% of cases of that primary with metastases	% of cases with only atypical metastases
Head/neck	14/24 (58.3)	4	4.5%	16.7%	19.0%
Back	20/40 (50)	5	4.4%	12.5%	23.8%
Lower extremity	15/54 (27.8)	6	5.8%	11.1%	28.6%
Anterior chest wall	5/12 (41.7)	2	6.1%	16.7%	9.5%
Ocular	5/20 (25)	0	0%	0%	0%
Upper extremity	4/8 (50)	1	3.4%	12.5%	4.8%
Pelvis	2/5 (40)	1	6.7%	20%	4.8%
Anorectal	1/3 (33.3)	0	0%	0%	0%
Sinonasal	1/3 (33.3)	0	0%	0%	0%
Anterior abdominal wall	0/1 (0)	0	0%	0%	0%
Labia/vagina	0/1 (0)	0	0%	0%	0%
Oral mucosa	0/0 (0)	0	0%	0%	0%
Enteric	0/0 (0)	0	0%	0%	0%
Unknown	4/10 (40)	2	13.3%	20%	0%