Contributed by Negar Khanlou, MD1, Randy Tashjian, MD1, Hrayr K Shahinian, MD, FACS2, Harry V Vinters, MD1
1Department of Pathology & Laboratory Medicine, Section of Neuropathology University of California, Los Angeles (UCLA) - David Geffen School of Medicine Los Angeles, CA 90095;
2Pituitary Center, The Skull Base Institute, 8635 W. 3rd Street, Los Angeles, CA 90048
We present the case of a 61-year-old male with a longstanding history of pituitary macro-prolactinoma medically treated with high dose cabergoline without significant reduction in tumor size. The pituitary lesion was first discovered more than 11 years prior to presentation and had been routinely monitored since that time with serial magnetic resonance imaging (MRI) scans and hormone profile testing. Pre-operative MRI in July 2014 revealed an enlarged, remodeled sella and a pituitary macroadenoma measuring approximately 2 cm in greatest dimension (Figure 1). Pre-operative laboratory values from March 2015 showed no evidence for an active neuroendocrine tumor. Detailed serology included a prolactin level of 7.6 ng/mL (reference range, 2.1 - 17.7 ng/mL) and a growth hormone level of 0.07 ng/mL (reference range, 0.01 - 0.97 ng/mL). Cortisol, adrenocorticotropic, luteinizing, and follicle stimulating hormones were also within normal serologic range. The patient underwent endoscopic endonasal resection of the pituitary mass, and a gross total resection was achieved. Intraoperatively, the lesion was described as extremely gritty and nodular. Post-operatively, the patient remained asymptomatic for several months despite a slight increase in his prolactin level to 8.9 ng/mL and remains asymptomatic to date almost one year post surgery. His postoperative endocrinologic pituitary hormonal profile is unchanged from his preoperative levels.
Histopathologic examination of the surgically resected specimen disclosed nodules of eosinophilic, partially calcified amorphous material (Figure 2). Separating each nodule were intervening septae of paucicellular, loose fibroconnective tissue containing very rare small collections of mononuclear inflammatory cells. Reticulin stain highlighted mainly an extensive collagenous background and no significant residual neuroendocrine tissue (Figure 3). Given the patient's clinical history, a panel of immunohistochemical stains was performed to evaluate for microscopic evidence for residual anterior pituitary and/or pituitary adenoma. Prolactin and growth hormone studies were non-reactive in the lesional tissue. What is your diagnosis?