Should Mesenteric Tumor Deposits Be Included in Staging of Small Intestine Neuroendocrine Tumors?
Raul S Gonzalez, Eric H Liu, M Kay Washington, Chanjuan Shi. Vanderbilt University Medical Center, Nashville, TN
Background: Small intestine neuroendocrine tumors (SI-NETs) are capable of widespread metastases before the primary tumor causes clinical symptoms. They have a propensity to spread to lymph nodes (LN) and the liver. They also can give rise to mesenteric tumor deposits (MTDs), though MTDs are not included in the current American Joint Committee on Cancer (AJCC) staging system for SI-NETs, and whether these MTDs are harbingers of distant metastases is unknown.
Design: Seventy-three SI-NET resections were identified in our files with slides and radiographic follow-up available. Each case was assessed for the presence or absence of LN metastases and MTDs, lymphovascular invasion (LVI), and liver metastases (pathologic and/or radiologic). AJCC T-stage was also noted. MTDs were defined as discrete mesenteric tumor nodules > 1mm with an irregular growth profile. Similar lesions clearly resulting from extranodal extension or direct contiguous spread by the primary lesion were excluded.
Results: Forty-four of the 73 SI-NET cases had MTDs (60%), which were typically adjacent to a large blood vessel and entrapping nerves. MTDs were significantly associated with LN metastases, liver metastases, LVI, and pT3 or pT4 disease (see table). Six cases (8%) had positive LNs and liver disease, but no MTDs, while 4 cases (5%) had MTDs and liver mets, but no LN disease. There were 9 cases with resected liver mets and no residual liver disease on post-surgical imaging; 5 had both LN mets and MTDs, and 4 had LN mets but no MTDs. All 4 cases with MTDs and no LN disease had residual liver disease on imaging (typically multiple lesions), while 4 of the 6 cases with LN disease and no MTDs had no residual liver disease on imaging, and the other 2 had quantifiable, rather than innumerable, lesions.
|MTD present||MTD absent||P-value|
|LN metastases||38/44 (86%)||18/29 (62%)||0.0236|
|Liver metastases||24/44 (55%)||6/29 (21%)||0.0070|
|LVI||41/44 (93%)||17/29 (59%)||0.0007|
|pT3 or pT4||40/44 (91%)||17/29 (59%)||0.0029|