An adrenal collision tumor or collision tumor of the adrenal gland is an uncommon condition where two histologically distinct tumors abut each other or are in close proximity in the same adrenal gland.
Collision tumors have been reported in nearly every organ, for example, collision tumor of the ovary. They may be composed of two primary tumors derived from the same organ, or a primary tumor and a metastasis. Given the high prevalence of adrenal adenoma, this is unsurprisingly the most often encountered component in adrenal collision tumors.
In terms of classification, collision tumors need to be distinguished from a composite tumor, where two different histologic types are intermixed.
The close approximation of two tumors not intermixed at their interface can create both diagnostic and therapeutic difficulties. A mixed benign and malignant collision tumor can render the malignant component unidentifiable on biopsy, with suboptimal or inappropriate treatment being the obvious consequence. It is, therefore, crucial to ensure that the lesion suspicious for malignancy be sampled amply.
It has been demonstrated that 18F-FDG PET, CT and MRI are all capable of readily distinguishing the two separate components of collision tumors within the adrenal gland. Chemical shift MRI may help in differentiating between benign lipid-poor adenomas and malignant tumors.
In the case of one component being an adrenal adenoma, definitive diagnosis of this component should be straightforward, given the high diagnostic accuracy of the aforementioned modalities for this lesion.
For a heterogeneous appearing adrenal mass consider:
- 1. Untch BR, Shia J, Downey RJ et-al. Imaging and management of a small cell lung cancer metastasis/adrenal adenoma collision tumor: a case report and review of the literature. World J Surg Oncol. 2014;12 (1): 45. doi:10.1186/1477-7819-12-45 - Free text at pubmed - Pubmed citation
- 2. Schwartz LH, Macari M, Huvos AG et-al. Collision tumors of the adrenal gland: demonstration and characterization at MR imaging. Radiology. 1996;201 (3): 757-60. Pubmed citation
- 3. Katabathina VS, Flaherty E, Kaza R et-al. Adrenal collision tumors and their mimics: multimodality imaging findings. Cancer Imaging. 2013;13 (4): 602-10. doi:10.1102/1470-7330.2013.0053 - Pubmed citation
- 4. Tappouni R, DeJohn L. AJR teaching file: enlarging adrenal mass previously characterized as an adenoma. AJR Am J Roentgenol. 2009;192 (6_supplement): S125-7. doi:10.2214/AJR.07.7016 - Pubmed citation