Nodular amyloidoma of the pituitary gland
Review of original standard histology evoked the possibility of extensive iatrogenic tumor fibrocalcinosis, localized fibrous tumor, psammomatous fibrous meningioma, and remotely calcified craniopharyngioma. However, these lesions have an abundance of collagen with a more coarsely fibrillar appearance than that observed in our case. Calcifications in this case were rare and only partially involved the nodular amorphous structures. A Congo red stain (with polarization) demonstrated green birefringence within the spheroidal structures (Figure 4) and easily distinguished extensive amyloid deposition from the morphologic mimickers. None of the aforementioned differentials would show extensive "nodular" amyloid deposition, either as primary association or as a secondary degenerative process.
Amyloidoma, also described by the terms "localized amyloid" or "amyloid tumor", represents a discrete mass that may be found in the cranial compartment, in the spinal canal, and in various other tissues and organs (4). Intracranial, extra-axial amyloidomas usually present as expansile masses in the cerebellopontine angle, jugular foramen, hypophyseal fossa, and the Gasserian ganglion (1). An association with history of prolactin producing pituitary adenoma is of interest in our patient. In the pituitary region scattered amyloid deposits are occasionally noted to be associated with such clinical background. However, nodular amyloid pseudotumors appear to be of a primary origin. Amyloidomas rarely present as mass lesions within the brain parenchyma (2). As expected, spinal lesions usually present with paraparesis, paraplegia or radiculopathy. Amyloidomas are most commonly composed of the immunoglobulin light chain type of amyloid, and even with long term follow-up, are generally not associated with the evolution of systemic amyloidosis, multiple myeloma, or neurocutaneous syndromes. Occasional studies, however, report the finding of monoclonal gammopathy in patients with intracranial amyloidoma, suggesting origin of the amyloid tumor in a "burnt out" plasmacytoma (3).
A localized intracranial amyloidoma is not associated with the deposition of distinctly central nervous system parenchymal and microvascular amyloid of the type observed in Alzheimer dementia and familial stroke syndromes associated with amyloid angiopathy. Amyloidomas of the skull base may be highly destructive, are extremely hypointense on T2-weighted images, and enhance variably after the administration of contrast medium. While rare, amyloidomas of the cranial space may mimic a neoplastic process. Early diagnosis is essential in preserving the quality of life in these patients who otherwise may be subjected to excessive medical intervention. Because intracranial, including intracerebral, amyloidomas are typically encountered unexpectedly by the Surgical Pathologist, detailed biochemical studies of these lesions are few in number. To date, no medical treatment has proven effective in patients with nodular amyloidoma.
Contributed by Negar Khanlou, MD, Randy Tashjian, MD<, Hrayr K Shahinian, MD, FACS, Harry V Vinters, MD