Pheochromocytomas and Ganglioneuromas in the Aging Rats: Morphological and Immunohistochemical Characterization

Abstract

We investigated, morphologically and immunohistochemically, 74 medullary adrenal tumors, including 64 pheochromocytomas (14 malignant and 50 benign), 9 ganglioneuromas, and 1 malignant schwannoma. The tumors were detected in 2-year-old Wistar and Sprague-Dawley rats from carcinogenicity studies. Morphologically, benign pheochromocytomas were characterized by monomorphic, small, basophilic cells with almost absence of mitoses. Malignant pheochromocytomas presented a low grade of pleomorphism, higher rate of mitoses, necrosis, infiltrative growth and in 1 case metastases in the lung. Ganglioneuromas were characterized by ganglion and neuron-like cells embedded in an eosinophilic matrix containing neurites, Schwann cells, and scant fibrovascular elements. All pheochromocytomas were strongly immunoreactive for tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. Subpopulations of chromaffin cells expressed chromogranin A (CGA) positivity. Matrix and Schwann cells were positive for S-100 and for glial fibrillary acidic protein (GFAP). In focal areas of the tumors, ganglion cells and axons were positive for neurofilament proteins (NFP) and synaptophysin. Ganglion cells exhibited peripherin and beta-tubulin. Proliferative activity of the tumors was assessed by immunostaining the endogenous cell proliferation associated-antigen Ki-67 and the proliferating cell nuclear antigen (PCNA). As expected, cell proliferation indices were much higher in malignant pheochromocytomas than in benign, yet ganglioneuromas remained immunonegative. Considering that Ki-67 antigen is more specific for cell proliferation, it should be regarded as marker of choice for supporting the differential diagnosis between benign and malignant pheochromocytomas.

Methodological Standardization for the Pre-Clinical Evaluation of Renal Sympathetic Denervation

“…Immunohistochemical staining for nerve fascicles should be considered in selected sections to evaluate for changes of neurotransmitters or axonal degeneration. Immunostains against S-100 protein (Marker for Schwann and sustentacular cells), neurofilament protein (Marker for neurons and ganglion cells), and glial fibrillary acidic protein (GFAP: Marker for glial cells) are used for the recognition of nerve fascicles (20), whereas stains targeted at tyrosine hydroxylase (TH; which converts tyrosine to DOPA) are used for the presence or absence of norepinephrine synthesis (21). Although DOPA decarboxylase (which converts DOPA to dopamine) is another catecholamine-synthesizing enzyme, immunostaining against DOPA decarboxylase is rarely used in the area of renal denervation because DOPA decarboxylase positive fibers are more sparsely distributed than TH positive fibers in perivascular nerves in the kidney (22).…”

Nonproliferative and Proliferative Lesions of the Rat and Mouse Endocrine System

“…( Aguzzi et al 1990 ; Botts et al 1994 ; Capen et al 2001 ; Duprat et al 1990 ; Faccini et al 1990 ; Frith 1996a ; Frith and Dunn 1994 ; Frith and Ward 1988b ; Hamlin II and Banas 1990 ; Hill et al 2003 ; Laroque et al 1997 ; Longeart 1996 ; Maita et al 1988 ; Majeed and Harling 1986 ; Nyska and Maronpot 1999 ; Pace et al 2002 ; Rosol et al 2013 ; Russfield 1967 ; Strandberg 1996d ; Unger et al 1990 ; Wright et al 1990 )…”

“…( Botts et al 1994 ; Capen et al 2001 ; Duprat et al 1990 ; Faccini et al 1990 ; Frith 1996a ; Frith and Dunn 1994 ; Frith and Ward 1988b ; Glaister et al 1977 ; Hamlin II and Banas 1990 ; Kiupel et al 2008b ; Laroque et al 1997 ; Longeart 1996 ; Molenaar et al 1990 ; Nyska and Maronpot 1999 ; Pace et al 2002 ; Patterson et al 1995 ; Reznik and Germann 1996a ; Reznik et al 1980 ; Rosol et al 2013 ; Russfield 1967 ; Shirai et al 2012 ; Tischler 1992 ; Tischler et al 1990 ; Wright et al 1990 )…”

Classification of Neural Tumors in Laboratory Rodents, Emphasizing the Rat

“…The differentiation of benign and malignant tumors is very difficult and should include the presence of metastases and invasion rather than reliance on cytological features. Evaluation of cell proliferation using Ki67 has been regarded as helpful in supporting the differential diagnosis between benign and malignant pheochromocytomas (Pace et al 2002).…”