An adrenal collision tumour or collision tumour of the adrenal gland is an uncommon tumour of the adrenal gland, where two histologically distinct tumours abut each other or are in close proximity.
Collision tumours have been reported in nearly every organ, for example collision tumour of the ovary. They may be composed of two primary tumours from the same organ, or a primary tumour and a metastasis. Given the high prevalence of adrenal adenoma, this is not surprisingly this is the most often encountered component in adrenal collision tumours.
In means of classification, collision tumours need to be distinguished from a composite tumour, where two different histologic types are intermixed.
The close approximation of two tumours without admixture at their interface can create both diagnostic and therapeutic difficulties. A mixed benign and malignant collision tumor can render the malignant component unidentified on biopsy, with sub-optimal treatment being the obvious consequence.
It has been demonstrated that 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-rich adenomas and malignant tumours.
In the case of one component being adrenal adenoma, definitive diagnosis of this component should be straightforward, given the high diagnostic accuracy of the aforementioned modalities in this entity.
For a heterogeneous appearing adrenal mass consider:
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