A composite somatotroph-corticotroph pituitary adenoma

A 76-year-old woman presented with enlargement and weakness of her hands and feet coarsening of facial features, proximal muscle weakness, and worsening of her noninsulindependent diabetes mellitus. Serum growth hormone, somatomedin-C, and prolactin levels were elevated. Thyroid function test results and serum cortisol and adrenocorticotropic hormone levels were within normal limits. Luteinizing and follicle-stimulating hormone levels were both low, suggesting possible partial hypopituitarism. Magnetic resonance imaging of the sella demonstrated a pituitary lesion that measured 2.2 x 1 x 0.5 cm; it partially obliterated the suprasellar cistern and it distorted the optic chiasm. Light microscopic and ultrastructural examination of the trans-sphenoidally resected tissues identified characteristic features of 2 discrete pituitary adenomas that were in close apposition, but they were sharply demarcated. The 2 components were a corticotroph adenoma and a sparsely granulated somatotroph adenoma. Multiple adenomas of the pituitary are not rare; however, the majority are endocrinologically "nonfunctional." We report a patient with clinical features of acromegaly whose tumor was a composite lesion: one area exhibited morphological characteristics of a corticotroph adenoma and another distinct area exhibited features of a somatotroph adenoma. The possible histogenesis is discussed.