Double separate versus contiguous pituitary adenomas: MRI features and endocrinological follow up

Double pituitary adenomas are defined as two adenomas within a gland. These have distinct light microscopic and immunohistochemical features and may be clearly-separate or contiguous. Most reports have focused on the various hormonal combinations in double tumors rather than on any potential increased risk for residual mass or endocrinopathy. Departmental files were searched to identify all double adenomas from 1/1/2000 to 3/1/2016, with review of magnetic resonance imaging (MRI) to determine if the dual nature of the lesions could be discerned retrospectively after histologic diagnosis of double adenoma. All cases were immunostained for standard anterior pituitary hormones. Eight cases were identified: 2 follicle-stimulating hormone (FSH)/alpha subunit (ASU) + prolactinoma (PRL); 1 PRL + corticotroph (ACTH); 1 hormone-negative + PRL; 1 ACTH + ASU/growth hormone (GH)/PRL; 1 GH/PR + PRL; 1 FSH/ASU, + ACTH; 1 GH + luteinizing hormone (LH). One patient had clearly-separate lesions identified preoperatively and required two surgical procedures for gross total resection. A second patient had 2 lesions recognized at surgery and afterwards on retrospective neuroimaging. The remaining 6 patients had double adenomas discovered at the time of histologic examination that were not resolvable at surgery or on retrospective neuroimaging. Four patients, 2 with clearly-separate and 2 with contiguous double adenomas, had persistent MRI abnormalities, and one had continued endocrine abnormalities. Double contiguous pituitary adenomas are difficult to anticipate preoperatively or to resolve intraoperatively. Although double contiguous adenomas are much more common than double separate lesions, both have a risk for subtotal resection and, thus, residual mass and/or endocrinopathy may ensue.