Synchronous Multiple Pituitary Neuroendocrine Tumors of Different Cell Lineages

We report clinicopathological features of a large series of synchronous multiple pituitary neuroendocrine tumors (PitNETs) of different cell lineages. Retrospective review of pathology records from 2001 to 2016 identified 13 synchronous multiple PitNETs from 1055 PitNETs classified using pituitary cell-lineage transcription factors, adenohypohyseal hormones, and other biomarkers. Clinical, radiological, and histopathological features of these tumors were reviewed. The series included seven females and six males. Mean age at diagnosis was 55.23 years (range 36-73). Imaging was unavailable for four patients; among the other nine, mean tumor size was 2.23 cm (range 0.9-3.9). Five patients had acromegaly, four had Cushing disease, and four had clinically non-functional tumors. Twelve had double PitNETs; one had a triple PitNET. The most common tumor type was corticotroph (n = 8; six densely and one sparsely granulated and one Crooke cell; three densely and one sparsely granulated were clinically silent), gonadotroph tumors (n = 8), and somatotroph tumors (n = 5; four sparsely granulated and one densely granulated somatotroph) were followed by lactotroph tumors (n = 4; all sparsely granulated), poorly differentiated Pit-1 lineage tumor (n = 1), and unusual plurihormonal tumor (n = 1). A 54-year-old man with Cushing disease had MEN1-driven Crooke cell and gonadotroph tumors. The triple pitNET consisted of a multilineage plurihormonal tumor associated with a gonadotroph and a sparsely granulated lactotroph tumor. The Ki67 (available from 10 specimens) ranged from 1 to 5% in individual tumors. Radiological and biochemical follow-up was available for 10 and 11 patients, respectively. Radiological tumor persistence/recurrence was identified in three patients with double PitNETs consisting of sparsely granulated lactotroph and gonadotroph tumors (n = 1), sparsely granulated somatotroph and silent corticotroph tumors (n = 1), and gonadotroph and silent corticotroph tumors (n = 1) with cavernous sinus invasion. Biochemical persistence was noted in four patients with double PitNETs consisting of sparsely granulated somatotroph and silent corticotroph tumors (n = 2), gonadotroph and Crooke cell tumors (n = 1), and densely granulated somatotroph and silent corticotroph tumors (n = 1). Multiple PitNETs represent about 1% of PitNETs and usually have hormone excess due to at least one tumor component. Clinical manifestations may be due to the minor component, especially in patients with Cushing disease. Invasive growth and aggressive histological subtypes predicted disease persistence/recurrence. This series also highlights the importance of routine application of pituitary cell lineage transcription factors along with hormones to distinguish and subtype multiple synchronous PitNETs.