A tumour deposit is a microscopic or macroscopic tumour nodule in the lymphatic drainage bed of the (primary) tumour. The term is applied in colorectal adenocarcinoma and has also been described in gastric cancer.
It is also known as discoutinuous extramural extension and peritumoural deposit.
Conceptually, tumour deposits are like the in-transit metastases of malignant melanoma and dermatopathology; however, it is important to note that on a practical level the specific (morphologic/clinical) definitions of tumour deposit and in-transit metastasis are different.
- Poor prognosticator.
- Can be understood as a type of invasive front/border, e.g. well-circumscribed border versus infiltrative border.
Definition - TNM/AJCC 8th edition for colorectal cancer: "Tumor deposits are defined as discrete tumor nodules within the lymph drainage area of the primary carcinoma without identifiable lymph node tissue or identifiable vascular or neural structure. The shape, contour, and size of the deposit are not considered in these designations."
Definition - TNM/AJCC 7th edition for colorectal cancer:
- Microscopic or macroscopic nodule in the lymphatic drainage bed of the tumour.
- No standardized distance (from tumour) criteria are defined.
- No findings suggestive of it being a lymph node replaced by tumour:
- No significant lymphoid tissue.
- Irregular contour.
- Round nodules of tumour are considered lymph nodes that are replaced by tumour.
- The definition of tumour deposit has changed significantly between the TMN/AJCC fifth, sixth, seventh editions.
- Lesions that are not in the drainage bed of the tumour are metastatic disease, pM1b.
Ueno et al. propose that a tumour deposit is either:
- >=2 mm from the tumour front.
- >=2 mm (radially) from the deepest aspect of the muscularis propria, if the tumour is not present in the plane of section.
Staging implications in colorectal cancer:
- Tumour deposits are not counted as (positive) lymph nodes and in the context of positive lymph nodes do not change the N stage.
- If no positive lymph nodes are present, the N stage is pN1c.
- The T stage is not affected by tumour deposits.
- Lee, HS.; Lee, HE.; Yang, HK.; Kim, WH. (May 2013). "Perigastric tumor deposits in primary gastric cancer: implications for patient prognosis and staging.". Ann Surg Oncol 20 (5): 1604-13. doi:10.1245/s10434-012-2692-9. PMID 23184289.
- Puppa, G.; Ueno, H.; Kayahara, M.; Capelli, P.; Canzonieri, V.; Colombari, R.; Maisonneuve, P.; Pelosi, G. (Mar 2009). "Tumor deposits are encountered in advanced colorectal cancer and other adenocarcinomas: an expanded classification with implications for colorectal cancer staging system including a unifying concept of in-transit metastases.". Mod Pathol 22 (3): 410-5. doi:10.1038/modpathol.2008.198. PMID 19136930.
- Ueno, H.; Hashiguchi, Y.; Shimazaki, H.; Shinto, E.; Kajiwara, Y.; Nakanishi, K.; Kato, K.; Maekawa, K. et al. (Oct 2013). "Peritumoral deposits as an adverse prognostic indicator of colorectal cancer.". Am J Surg. doi:10.1016/j.amjsurg.2013.04.009. PMID 24112678.
- Nagtegaal, ID.; Tot, T.; Jayne, DG.; McShane, P.; Nihlberg, A.; Marshall, HC.; Påhlman, L.; Brown, JM. et al. (Jun 2011). "Lymph nodes, tumor deposits, and TNM: are we getting better?". J Clin Oncol 29 (18): 2487-92. doi:10.1200/JCO.2011.34.6429. PMID 21555695.