**Core Concept**
The diagnosis and management of adrenal incidentalomas, particularly in the context of a functioning adrenal mass, requires a thorough evaluation to determine the likelihood of malignancy or functional status. The patient's clinical presentation, laboratory findings, and imaging characteristics are crucial in guiding the next steps.

**Why the Correct Answer is Right**
To determine whether the adrenal mass should be resected, the next step is to assess the functional status of the mass. Given the patient's normal blood pressure, absence of Cushing syndrome, and normal serum potassium levels, it is essential to evaluate for potential hyperfunctioning states such as aldosteronism or pheochromocytoma. The patient's normal erectile function also suggests that the mass is unlikely to be a functioning cortisol-producing adenoma. In this scenario, **B. Perform dexamethasone suppression test** is the appropriate next step to evaluate for subclinical cortisol hypersecretion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a CT scan with contrast is already performed, and further imaging is not necessary at this stage. The next step is to evaluate the functional status of the mass rather than ordering additional imaging.

**Option C:** This option is incorrect because the patient's serum potassium is normal, making hyperaldosteronism (Conn's syndrome) less likely. Additionally, the absence of hypertension and other clinical features of primary aldosteronism makes this diagnosis less probable.

**Option D:** This option is incorrect because the patient's normal blood pressure and absence of symptoms suggestive of pheochromocytoma (e.g., hypertension, headaches, palpitations) make this diagnosis less likely. However, a pheochromocytoma crisis can occur during surgery, so it is essential to rule out this diagnosis before resection.

**Clinical Pearl / High-Yield Fact**
In patients with adrenal incidentalomas, it is essential to evaluate for subclinical cortisol hypersecretion using a dexamethasone suppression test, as this can have significant implications for management and surgical decision-making.

**Correct Answer:** B. Perform dexamethasone suppression test.