LAUSR

Background: Pituitary carcinomas are rare neoplasms whose designation requires demonstration of metastatic disease. No specific morphologic features can reliably distinguish pituitary carcinomas from pituitary adenomas, rendering the diagnosis particularly challenging. Furthermore, as reports of pituitary carcinoma on fine needle aspiration (FNA) biopsy are exceedingly rare in the literature, the cytological features of pituitary carcinoma are poorly characterized. Case Report: Here we describe a case of pituitary carcinoma in a 67-year-old woman with history of recurrent adrenocorticotropic hormone (ACTH)-producing pituitary adenoma who presented with a persistent left cervical nodule for 2 years. Ultrasound-guided FNA of the nodule consisted of loosely cohesive clusters of epithelioid cells with marked cytologic atypia, intermediate to large nuclei, relatively irregular nuclear contour, coarse granular chromatin, prominent nucleoli, and delicate finely granular cytoplasm. Immunohistochemical stains performed on the cell block revealed positivity for synaptophysin, chromogranin and ACTH with an increased Ki-67 proliferation index (approximately 25%). Review of the patient's previously resected pituitary tumor showed similar cytomorphologic features. Conclusion: Given the similar cytologic features of pituitary carcinomas compared to other neuroendocrine tumors, it is important to obtain a complete clinical history and maintain a high index of suspicion in order to make a correct diagnosis of pituitary carcinoma on FNA.