TY - JOUR
T1 - Mucosal colonization by metastatic carcinoma in the gastrointestinal tract
T2 - A potential mimic of primary neoplasia
AU - Estrella, Jeannelyn S.
AU - Wu, Tsung Teh
AU - Rashid, Asif
AU - Abraham, Susan C.
PY - 2011/4
Y1 - 2011/4
N2 - The gastrointestinal (GI) tract is a common site for both primary and metastatic carcinomas. Distinguishing the two can occasionally be difficult, particularly when metastatic tumor reaches the mucosal surface. Features that are typically used to make this distinction include the presence of an adenomatous precursor lesion, regional lymph node involvement, and gross configuration of the tumor. However, we recently encountered 2 index cases of metastatic carcinoma in the small intestine (1from the colorectum and 1 of endocervical origin) that were initially misinterpreted as primary small bowel carcinomas because of apparent in situ growth in the mucosal surface resembling polypoid, adenomatous precursor lesions. We, therefore, studied 100 GI resections from 1987 to 2009 that were reported to show mucosal involvement by metastatic carcinoma, and compared the histologic features with a control group of 29 primary small bowel adenocarcinomas. Gross descriptions and histologic sections were evaluated for the following: (1) tumor spread along an intact basement membrane of villi/crypts (mucosal colonization), (2) resemblance to an adenoma/precursor lesion, (3) gross configuration of the tumor, (4) lymphovascular invasion, and (5) regional lymph node involvement in the metastatic site. Metastatic sites included the small intestine (n=74), colorectum (n=16), or both (n=10). Primary tumors were GI (n=55, with 47 from colorectum), gynecologic (n=28), pulmonary (n=8), genitourinary (n=6), head and neck (n=2), and breast (n=1). Overall, 42 (42%) of the metastases that reached the mucosal surface of the bowel showed at least focal mucosal colonization, 26% resembled a precursor adenoma, 62% had regional lymph node positivity, and only 24% cases showed a classic serosal-based configuration. In 4 cases (2 of GI origin and 2 of gynecologic origin), metastatic tumors were initially interpreted as new primaries by the pathologist (n=2) or clinicians (n=2). Metastatic carcinomas originating from the GI tract were significantly more likely to show mucosal colonization (60% vs. 20%, P<0.0001) and resemblance to a precursor lesion (45% vs. 2%, P<0.0001) than other primary tumors. In a comparison between 29 primary small bowel carcinomas and 41 metastatic colorectal carcinomas in the small bowel, metastatic tumors were distinguished by a higher prevalence of multiple lesions (0% vs. 39%, P<0.0001), whereas small bowel primaries were more likely to show high tumor grade (41% vs. 17%, P=0.03). There were no significant differences in the mean age (61.4 y vs. 60.9 y), number of male participants (69% vs. 56%), growth along basement membranes (62% vs. 63%), apparent precursor lesion (55% vs. 46%), lymphovascular invasion (69% vs. 73%), or lymph node positivity (68% vs. 37.5%, P=0.065). These results confirm that metastatic carcinomas involving the mucosal surface of the intestines frequently exhibit gross and histologic features, which mimic second primaries, especially when they originate from the GI tract. In situ growth and presence of an apparent adenoma cannot be taken as prima facie evidence of a primary neoplasm.
AB - The gastrointestinal (GI) tract is a common site for both primary and metastatic carcinomas. Distinguishing the two can occasionally be difficult, particularly when metastatic tumor reaches the mucosal surface. Features that are typically used to make this distinction include the presence of an adenomatous precursor lesion, regional lymph node involvement, and gross configuration of the tumor. However, we recently encountered 2 index cases of metastatic carcinoma in the small intestine (1from the colorectum and 1 of endocervical origin) that were initially misinterpreted as primary small bowel carcinomas because of apparent in situ growth in the mucosal surface resembling polypoid, adenomatous precursor lesions. We, therefore, studied 100 GI resections from 1987 to 2009 that were reported to show mucosal involvement by metastatic carcinoma, and compared the histologic features with a control group of 29 primary small bowel adenocarcinomas. Gross descriptions and histologic sections were evaluated for the following: (1) tumor spread along an intact basement membrane of villi/crypts (mucosal colonization), (2) resemblance to an adenoma/precursor lesion, (3) gross configuration of the tumor, (4) lymphovascular invasion, and (5) regional lymph node involvement in the metastatic site. Metastatic sites included the small intestine (n=74), colorectum (n=16), or both (n=10). Primary tumors were GI (n=55, with 47 from colorectum), gynecologic (n=28), pulmonary (n=8), genitourinary (n=6), head and neck (n=2), and breast (n=1). Overall, 42 (42%) of the metastases that reached the mucosal surface of the bowel showed at least focal mucosal colonization, 26% resembled a precursor adenoma, 62% had regional lymph node positivity, and only 24% cases showed a classic serosal-based configuration. In 4 cases (2 of GI origin and 2 of gynecologic origin), metastatic tumors were initially interpreted as new primaries by the pathologist (n=2) or clinicians (n=2). Metastatic carcinomas originating from the GI tract were significantly more likely to show mucosal colonization (60% vs. 20%, P<0.0001) and resemblance to a precursor lesion (45% vs. 2%, P<0.0001) than other primary tumors. In a comparison between 29 primary small bowel carcinomas and 41 metastatic colorectal carcinomas in the small bowel, metastatic tumors were distinguished by a higher prevalence of multiple lesions (0% vs. 39%, P<0.0001), whereas small bowel primaries were more likely to show high tumor grade (41% vs. 17%, P=0.03). There were no significant differences in the mean age (61.4 y vs. 60.9 y), number of male participants (69% vs. 56%), growth along basement membranes (62% vs. 63%), apparent precursor lesion (55% vs. 46%), lymphovascular invasion (69% vs. 73%), or lymph node positivity (68% vs. 37.5%, P=0.065). These results confirm that metastatic carcinomas involving the mucosal surface of the intestines frequently exhibit gross and histologic features, which mimic second primaries, especially when they originate from the GI tract. In situ growth and presence of an apparent adenoma cannot be taken as prima facie evidence of a primary neoplasm.
KW - Gastrointestinal metastasis
KW - adenoma
KW - in situ growth
KW - mimic
KW - mucosal colonization
KW - small bowel adenocarcinoma
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U2 - 10.1097/PAS.0b013e318211b3d2
DO - 10.1097/PAS.0b013e318211b3d2
M3 - Article
C2 - 21412071
AN - SCOPUS:79953199352
SN - 0147-5185
VL - 35
SP - 563
EP - 572
JO - American Journal of Surgical Pathology
JF - American Journal of Surgical Pathology
IS - 4
ER -