Introduction: The identification of a significant adrenal mass in a patient without a biopsy-confirmed malignancy poses a diagnostic challenge: Is it a metastatic lesion or an underlying adrenal condition? Adrenal metastases are the second most common site of spread for lung adenocarcinoma; approximately 3–7% of adrenal masses represent benign adenomas. Diagnosis is even harder if there are signs of primary aldosteronism (PA). Case: We present a case of a 62-year-old Chinese female with a 10-year history of hypertension, managed on dual antihypertensive therapy, who presented for evaluation of suspected PA following the discovery of hypokalemia. Biochemical screening revealed an elevated aldosteronerenin ratio (ARR, 65). The overnight dexamethasone suppression test (20 nmol/L) and testosterone (0.79 nmol/L) were both within normal limits. Saline Suppression Test (SST) showed an indeterminate post-infusion aldosterone level (202.8 pmol/L). Cross-sectional imaging via computed tomography (CT) Adrenals identified a large, 6.4 × 5.4 × 6.2 cm heterogeneous left suprarenal mass with a low mean attenuation (8.6 Hounsfield Unit [HU]). Concurrently, an incidental left upper lobe pulmonary lesion was identified, and PET-CT was performed; the SUVmax of the lung was identical to that of the adrenal lesion. An ultrasoundguided biopsy of the pulmonary lesion confirmed estimated glomerular filtration rate-mutation-positive lung adenocarcinoma. The patient started on targeted therapy with dacomitinib. Follow-up CT imaging at 9 months demonstrated disease progression within the thorax, marked by the appearance of a new pulmonary nodule. Notably, however, the adrenal mass remained stable in size and morphology. Conclusion The absence of mixed androgen/glucocorticoid hypersecretion, combined with the radiographically static nature of the mass, suggests a lower probability of adrenocortical carcinoma. This case highlights that while size is a major risk factor for adrenocortical carcinoma, it must be interpreted in conjunction with hormonal activity, HU, and growth patterns. Identifying these “mimics” helps avoid over-staging lung cancer and ensures patients receive targeted therapy instead of unnecessary adrenalectomies.