Gastric Collision Tumors: An Insight into Their Origin and Clinical Significance

Abstract

Collision tumors are rare neoplasms displaying two distinct cell populations developing in juxtaposition to one another without areas of intermingling. They are rare entities with only 63 cases described in English literature. Tumors encountered are gastric adenocarcinomas colliding with lymphomas, gastrointestinal stromal tumors, squamous cell carcinomas, and neuroendocrine tumors. Their cell origin is obsolete by the time of diagnosis. Different tumorigenesis theories have been suggested to explain their behavior, yet none has managed to provide satisfactory explanation for all cases. Clinically they are indistinguishable from the dominant tumor. Lack of data does not allow detailed assessment of their behavior yet they seem aggressive neoplasms with dismal prognosis. The majority of cases have been diagnosed postoperatively during histologic examination of specimens. There are no guidelines or concrete evidence to support best way of adjuvant or other types of treatment. However, these rare neoplasms might help in unlocking secrets of cancer behavior including tumorigenesis, differentiation, and adhesion and thus clinicians should be aware of their existence.

Collision Tumors of the Gastrointestinal Tract: A Systematic Review of the Literature

“…However, several studies reported a biphasic pattern of infiltration, where both components of the CT coexisted (18-20, 54, 55). A possible explanation could be that metastasis took place before the final differentiation of the distinct histological subtypes (10). There are also cases in which each of the components metastasized to different lymph node groups (29,31).…”

“…types are minimal and it is difficult to distinguish between them (1,10,11). This is why many researchers use all the above terms interchangeably.…”

A Collision Tumor With Features of Breast Cancer and Plasma Cell Myeloma as Primary Tumors

“…The cause of collision tumors such as that in our patient is unclear. Of course, coincidence is a possibility with the unfortunate meeting of two coexisting neoplasms developing independently and finally colliding [12]. This theory does not provide any particular explanation of the colliding pattern and makes no differentiation between composite and collision neoplasms [12].…”

Gastric Collision Tumor of Adenocarcinoma and MALT Lymphoma: A Rare Coincidence or Proof of <i>H. pylori</i> Incrimination?

“…In this subtype, these two distinct neoplasms develop in juxtaposition to one another, without areas of intermingling [3]. In the literature, only 26 cases of gastric adenocarcinomas colliding with lymphomas have been reported [8].…”