Online Articles: Case ReportACTH-Cell Pituitary Adenoma With Signet Ring Cells: A Rare Case Report and Review of The LiteratureTrabzonlu, Levent MD*; Agirlar Trabzonlu, Tugce MD†; Gurbuz, Yesim MD‡; Ceylan, Savas MD§Author Information *Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD Departments of †Radiology ‡Pathology §Neurosurgery, Kocaeli University School of Medicine, Kocaeli, Turkey The authors declare no conflict of interest. Reprints: Levent Trabzonlu, MD, Department of Pathology, Johns Hopkins University School of Medicine, 1550 Orleans Street, Baltimore, MD 21287 (e-mail: email@example.com). Applied Immunohistochemistry & Molecular Morphology: February 2020 - Volume 28 - Issue 2 - p e13-e16 doi: 10.1097/PAI.0000000000000639 Buy Metrics Abstract Here, we present a case of pituitary adenoma producing adrenocorticotropic hormone (ACTH) in a 19-year-old woman. The patient was admitted to neurosurgery clinic because of a headache and decreased visual acuity. Transsphenoidal resection was performed. Microscopic examination of the tumor revealed signet-ring-like cell areas intermixed with conventional pituitary adenoma cells. Both populations of tumor cells showed immunoreactivity for chromogranin, synaptophysin, and ACTH. To date, there have been 3 reports of pituitary adenoma with signet-ring-like changes. To our knowledge, this is the first case of ACTH-secreting pituitary adenoma with signet-ring-like cell changes. The clinical reflection of signet cells in pituitary adenoma is unclear. Accumulation of the similar cases and investigation of molecular background of them may lighten the importance of this morphologic variance. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.