**Core Concept**
The question is testing knowledge of orbital masses, specifically the most common type found in adults. Orbital masses can arise from various tissues, including bone, muscle, fat, blood vessels, and nerves. The correct answer is related to the most frequent type of non-neoplastic orbital mass.

**Why the Correct Answer is Right**
The most common retrobulbar orbital mass in adults is a **cavernous hemangioma**. This benign vascular lesion arises from the vascular channels within the orbital fat. The pathophysiology involves the abnormal proliferation of vascular endothelial cells, leading to the formation of blood-filled cavities. Cavernous hemangiomas are typically found in the retrobulbar region, behind the globe of the eye, and are often asymptomatic. They are usually identified incidentally during imaging studies performed for unrelated reasons.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because lymphoma is a type of malignant tumor that can affect the orbit, but it is not the most common retrobulbar orbital mass in adults.
* **Option B:** This option is incorrect because a dermoid cyst is a type of congenital orbital mass that typically presents in childhood, not adulthood.
* **Option D:** This option is incorrect because a meningioma is a type of benign tumor that can arise from the meninges, but it is not the most common retrobulbar orbital mass in adults.

**Clinical Pearl / High-Yield Fact**
Cavernous hemangiomas are benign lesions, but they can cause visual disturbances or proptosis if they become large enough to compress adjacent structures. Imaging studies, such as MRI or CT scans, are essential for diagnosing cavernous hemangiomas and distinguishing them from other orbital masses.

**Correct Answer: C. Cavernous hemangioma**