Kollisionstumor der Nebennieren

Imaging and

management of a small cell lung cancer metastasis/adrenal adenoma collision tumor: a case report and review of the literature. Pretreatment imaging of an adrenal collision tumor. (A) Non-contrast axial computed tomography scan (CT) demonstrating two distinct lesions in the left adrenal gland: a low attenuation 2.9 × 3.1-cm lesion as well as a higher attenuation 1.2 × 1.4-cm nodule, suspicious for metastatic disease. (B) Fused CT/fluorodeoxyglucose (FDG) positron emission tomography scan demonstrates an FDG avid lesion in the high attenuation component (standardized uptake value (SUVmax) 7) and no significant uptake in the low attenuation component. (C) Opposed-phase axial magnetic resonance imaging shows loss of signal intensity in the majority of the left adrenal mass, consistent with a lipid-rich adrenal adenoma, largely surrounding a 1.2-cm mass within the lateral portion of the adrenal gland that did not lose signal intensity, suggestive of metastatic disease.

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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.

Pathology

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.

Clinical significance

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.

Radiographic assessment

It has been demonstrated that F-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.