Adrenal pheochromocytoma mimicking small cell carcinoma on fine needle aspiration biopsy. A case report

BACKGROUND: Fine needle aspiration biopsy (FNAB) is a sensitive and specific technique in the diagnosis of adrenal tumors. However, in rare cases the cytomorphologic features may mimic small cell neoplasms. CASE: A 54-year-old male presented with a history of hypertension and left flank pain of recent onset. Abdominal computed tomography (CT) showed a 4-cm mass involving the left adrenal gland. Fine needle aspiration biopsy (FNAB) showed groups of small round cells with hyperchromatic nuclei. The findings were highly suspicious for metastatic small cell carcinoma. Subsequently it was learned that the mass had been noted three years earlier on CT studies but had grown from 2.5 to 4 cm. A chest radiograph was unremarkable. The clinical findings were more in keeping with a primary adrenal tumor. Immunohistochemical staining done retrospectively on the cell block showed positive reactivity for chromogranin and neuron-specific enolase. These findings, correlated with the clinical features, were in keeping with a diagnosis of pheochromocytoma. Left adrenalectomy revealed a pheochromocytoma. CONCLUSION: Adrenal pheochromocytoma should be included in the differential diagnosis of small round cell neoplasms seen on FNAB of the adrenal gland. Immunohistochemistry and clinical findings are helpful in reaching the correct diagnosis.