AFIP Wednesday Slide Conference - No. 8
27 October 1999

Conference Moderator:
Dr. Jerrold Ward
Diplomate, ACVP
National Cancer Institute
Fairview 201, PO Box B
Frederick, MD 21702-1201
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Case I 99-8172 (AFIP 2695446)
Signalment: 18-week-old, C57BL/6L viable motheaten male mouse (Mus musculus) (Hcph me-v/Hcph me-v = mev/mev = viable motheaten)
History: This mouse was from a mutant colony maintained at the Jackson Laboratory.
Gross Pathology: The lungs were mottled reddish-brown, the spleen was enlarged and the feet had patchy areas of tan, thickened exudative lesions. There was a generalized patchy loss of hair.

Contributor's Diagnosis and Comments: Acidophilic macrophage pneumonia.

The viable motheaten spontaneous autosomal recessive mutation on chromosome 6 disrupts the hematopoietic cell phosphatase (Hcph) gene. Hcph encodes the SHP-1 protein-tyrosine phosphatase, which is primarily expressed in hematopoietic cells. SHP-1 is a critical negative regulator in multiple signaling pathways in the hematopoietic and immune systems.
Viable motheaten mice develop systemic autoimmunity, anemia and immunodeficiency. Pathology includes severe inflammatory lesions in the skin and lungs. These lesions, comprised mainly of macrophages and granulocytes, are not associated with infection and occur even under specific pathogen-free husbandry conditions. T- and B-lymphocytes are not required for the development of these lesions as evidenced by the persistence of these inflammatory lesions in mice doubly homozygous for viable motheaten and severe combined immunodeficiency mutations.
A number of signaling pathways in monomyeloid cells are regulated through the phosphorylation of tyrosine residues in growth factor receptors and other proteins, resulting in activation of the pathway. The dephosphorylation of tyrosine residues and subsequent deactivation of this pathway maintains normal homeostasis. In viable motheaten mice, which are deficient in SHP-1, tyrosine residues are not dephosphorylated, thus preventing down regulation of the signaling pathway resulting in proliferation of monomyeloid cells.
Treatment of viable motheaten mice with anti-MAC-1-antibody inhibits the development of inflammatory lesions, thus supporting a role for monomyeloid cells in the pathogenesis of this disease. Additionally, in-vitro studies have shown several hematopoietic growth factors, including CSF-1, G-CSF and GM-CSF, to enhance proliferation of bone marrow progenitor cells from viable motheaten mice as compared to littermate controls.
Trichrome staining of lung sections from viable motheaten mice demonstrates increased intra-alveolar and interstitial collagen deposition. The interstitial fibrosis noted in the lung lesions has been associated with increased TNF-alpha in macrophages and serum of viable motheaten mice. The relationship between elevated TNF-alpha and macrophage dysfunction is unclear; however, TNF-alpha has been shown to stimulate the proliferation of fibroblasts and increase collagen synthesis.
Eosinophilic amorphous and crystalline structures are seen free in the alveoli and contained within macrophages in the lungs of viable motheaten mice. Gormori's iron stain does reveal hemosiderin within macrophages; however, the crystalline structures do not stain for iron. These crystals do not fluoresce in ultraviolet light and are not birefringent with polarized light. It is believed that this eosinophilic material is a blood breakdown product or it may result from defective macrophage catabolism of surfactant.
The pulmonary pathology of viable motheaten mice is just one manifestation of their disease. This mutant mouse is the first animal model of a specific protein-tyrosine phosphatase deficiency and provides the opportunity to elucidate the regulatory mechanisms of the hematopoietic and immune systems.
AFIP Diagnosis: Lung: Alveolitis, granulomatous, diffuse, moderate, with abundant eosinophilic intrahistiocytic crystalline material and brown granular intrahistiocytic pigment, C57BL/6L viable motheaten mouse (Mus musculus), rodent.
Conference Note: Participants agreed with the contributor's interpretation of the lesion. Eosinophilic crystals may be found in the lungs and alveolar macrophages of normal mice and in mice with various diseases to include experimental oxygen toxicity and Toxocara canis infection. Mice with Chediak-Higashi syndrome may have crystals within granulocytes and monocytes. Alveolar macrophage crystals are also reported in the lungs of human smokers. In most cases of murine pneumonia with eosinophilic crystals, the cause of crystal formation is unknown.
Viable motheaten mice also commonly have lymphoid depletion/necrosis of thymus from 3-10 weeks of age, absence of lymphoid follicles in lymph nodes, depletion of white pulp in spleen, elevated erythropoiesis in spleen, increased myelopoiesis in the bone marrow, glomerulonephritis, focal abscesses in the skin, decreased Leydig cells and decreased testosterone.
Contributor: The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609-1500
1. Shultz L, Rajan T Greiner D: Severe defects in immunity and hematopoiesis caused by SHP-1 protein-tyrosine-phosphatase deficiency. Tibtech Vol. 15:302-307, 1997
2. Shultz L, Coman DR, Bailey CL, Beamer WG, Sidman CL: "Viable Motheaten," a new allele at the motheaten locus. Am J Path Vol.116 (2):179-192, 1984
3. Thrall R, Vogel S, Evans R, Shultz L: Role of tumor necrosis factor-alpha in the spontaneous development of pulmonary fibrosis in viable motheaten mutant mice. Am J Path 151(5):1303-1310, 1997
4. Ward J: Pulmonary pathology of the motheaten mouse. Vet Path 15:170-178, 1978
5. Yank YH, Campbell JS: Crystalline excrements in bronchitis and cholecystitis of mice. Amer J Path 45: 337-345, 1964
Case II 99-000068, 69-12, -12, 88-12, 89-12, 90-12 (AFIP 2694694)
Signalment: B6, 129 (C57BL/6 X 129) male mice, 20-23 months of age.
History: Aging study, incidental findings.
Contributor's Diagnosis and Comments: Dental dysplasia, various degrees in different sections, unilateral or bilateral. Other lesions in some slides include Harderian gland hyperplasia/adenomas and inflammation. Dental dysplasia is a common lesion in many strains of mice. It has not been noted in many studies. Up to 25% of 2-year-old Balb-C mice have unilateral or bilateral dental dysplasia.
AFIP Diagnoses:
1. Teeth: Dental dysplasia, B6,129(C57/BL6 x 129) mouse, rodent.
2. Harderian gland: Papillary cystadenoma.
3. Harderian gland: Adenitis, lymphoplasmacytic, multifocal, mild.
4. Auditory canal: Otitis externa, ulcerative and suppurative, multifocal, moderate.
Conference Note: Mice have one set of teeth that grow and erupt continuously throughout life. The normal dentition for a mouse is one incisor and three molars in each quadrant; therefore, the dental formula is 2(I1/1, M3/3) = 16. The incisors grow at a rate of 2-3mm/week under normal conditions and up to 9mm/week as an adaptive response.

Destruction and inflammation of the tooth pulp results in proliferation of odontoblasts, cementoblasts and osteoblasts that produce disorganized masses of dental material in an attempt to repair the tooth. Factors that have been associated with development of dental dysplasia are consumption of powered feeds, malocclusion, frequent trimming, trauma, chronic inflammation and increased age. Maxillary incisors are more prone to dysplasia than mandibular incisors as they are seated in softer bone., Therefore, they are more easily damaged.
Some sections contain significant inflammation in association with the dental dysplasia. This may support the theory that dental dysplasia develops in response to chronic inflammation. In addition, some sections contain benign proliferative lesions of the Harderian glands. One examined in conference contained a papillary cystadenoma. Harderian gland neoplasms have been reported to occur in up to 75% of adult 129 black mice.

Contributor: National Cancer Institute, Fredrick, MD

1. Long PH, Leininger JR: Teeth. In: Pathology of the Mouse, ed. Maronpot RR, Boorman GA, Gaul BW, pp.13-22. Cashe River Press, Vienna, IL, 1999
2. Losco PE: Dental Dysplasia in rats and mice. Tox Patho, 23(6):677-688, 1995
Case III Case 1/160947-493/NIEHS (AFIP# 2677919)
Signalment: Two-year-old female Fischer 344 rat.
History: Tissue from a 2-year old female rat sacrificed at the end of a 2-year toxicity/ carcinogencity study. Administration of the chemical by gavage for 2 years resulted in a dose-related increase in the incidence of hyperplasia and benign and malignant neoplasms of the glandular stomach.
Gross Pathology: The fundic region of the glandular stomach was diffusely thickened and the mucosal surface appeared rough and granular.

Contributor's Diagnoses and Comments: Glandular stomach - Malignant neuroendocrine tumor (carcinoid).
Extensive areas of the fundic mucosa of the glandular stomach are thickened by a densely cellular neoplasm that has effaced the glandular epithelium and multifocally has invaded through the muscularis mucosa into the submucosa. The epithelium of the gastric pits is not affected. The neoplasm is composed of 2 morphologically distinct cell types. The larger population is composed of large polygonal cells arranged in sheets, nodular aggregates, small clusters, and well to poorly defined glandular structures. The cells have finely granular, lightly eosinophilic, amphophilic cytoplasm with pleomorphic nuclei and single nucleoli. The second cell population occurs as focally extensive sheets or variably-sized nodular aggregates of large polygonal cells characterized by intensely eosinophilic granular cytoplasm and single round to oval vesicular nuclei with 1 or 2 prominent nucleoli. Multifocally, both cell types occlude submuscosal blood vessels and lymphatics. The number of mitotic figures is low.
The majority of the benign and malignant neoplasms in this study were composed of cells that were morphologically consistent with neuroendocrine or enterochromaffin-like cells, and frequently, were accompanied by focal or multifocal proliferations (hyperplasia) of similar cells in the deeper one-third of the fundic mucosa extending toward the mucosal surface. Together the hyperplastic lesions and neoplasms appeared to form a morphologic continuum from preneoplasia to neoplasms. An additional consistent finding in this study was marked atrophy of the fundic mucosal epithelium due primarily to loss of parietal cells and chief cells to a lesser extent. Parietal cell degeneration and necrosis were evident in 90-day (subchronic) studies conducted earlier. Based on the morphologic, histochemical (Sevier-Munger) and immunohistochemical (neuron specific enolase and chromogranin-A) characteristics, the lesions were diagnosed as neuroendocrine cell hyperplasia and benign and malignant neuroendocrine tumors (carcinoids) of the glandular stomach.
As a group, spontaneous and chemically induced neuroendocrine proliferative lesions of the stomach are extremely rare in commonly used laboratory rodents. However, spontaneous malignant neuroendocrine neoplasms develop with high frequency in the wild rodent Praomys (Mastomys) natelensis, and this species has been used as a model for neuroendocrine neoplasia.
Neuroendocrine proliferative lesions arise from neuroendocrine or enterochromaffin-like (ECL) cells that are sparsely dispersed among the glandular epithelial (parietal and chief) cells in the deepest third of fundic mucosa. The exact functional role of ECL cells is not known; however, these cells are known to synthesize, store and secrete histamine and may also function in stimulating gastric acid secretion. ECL cells are specifically immunoreactive for neuron specific enolase and chromaganin-A; and are argyrophylic with the Sevier-Munger and Grimelius stains. These stains are commonly used to identify neuroendocrine tumors in the glandular stomach.
Experimentally, neuroendocrine proliferative lesions have been induced in the fundic stomach by the administration of antisecretagogues that produced prolonged inhibition of gastric acid secretion and achlorhydria. Such compounds include those that are proton pump inhibitors and histamine H2 receptor antagonists.
The proposed mechanism for the development of neuroendocrine lesions is thought to be related to the regulatory effects of circulating gastrin, which in addition to being a potent stimulator of gastric acid secretion, has a generalized trophic effect on the fundic glandular mucosa, in particular, the ECL cells. It is thought that gastric neuroendocrine proliferative lesions which develop in rats after prolonged inhibition of gastric secretion do so through the secondary mechanism of hypergastrinemia. A negative feedback control exists between gastric acidity and gastrin secretion by G-cells in the pylorus. An increase in gastric pH under the influence of potent inhibitors of gastric acid secretion results in secretion of gastrin by antral G-cells leading to hypergastrinemia, and subsequently, growth stimulation of ECL cells. With prolonged acid inhibition and hypergastrinemia, there is ECL cell hyperplasia which, when sustained, results in the development of neuroendocrine neoplasms. Direct stimulation of chief cells, or of a glandular epithelial stem cell population, may explain the presence of other glandular epithelial cell populations that are often components of these neoplasms.
In this study, atrophy of the fundic mucosa due to profound loss of parietal cells may have been the critical event leading to the induction of neoplasia. Loss of parietal cell mass most likely resulted in marked gastric hypochlorhydria, an increase in intragastric pH, and consequently hypergastrinemia. The trophic effect of prolonged hypergastrinemia on the fundic mucosa resulted in sustained proliferation of ECL cells leading ultimately to the development of proliferative neuroendocrine lesions. This proposed mechanism was supported by the results of additional 90-day studies which were conducted to elucidate possible mechanism(s) involved in the development of the neoplasms. We observed time and dose-dependent increases in intragastric pH and circulating gastrin levels in addition to morphologic evidence of progressive parietal cell degeneration and necrosis, and mucosal atrophy.
AFIP Diagnosis: Stomach: Neuroendocrine carcinoma (malignant carcinoid), Fischer 344 rat, rodent.
Conference Note: Based on histomorphology, conference participants considered the differential diagnosis of gastric carcinoma, metastatic pancreatic carcinoma and neuroendocrine carcinoma (malignant carcinoid). The Churukian-Schenk method was performed at the AFIP and demonstrated numerous argyrophilic granules within neoplastic cells, supporting the diagnosis of neuroendocrine carcinoma.

Contributor: National Institute of Environmental Health Sciences, PO Box 12233, Research Triangle Park, NC 27709
1. Betton GR, Domer CS, Wells T, Pert P, Price CA, Buckley PP: Gastric ECL-cell hyperplasia and carcinoids in rodents following chronic administration of H2-antagonists SK&F 93479 and oxmetidine and omeprazole. Tox Pathol 16(2):288-298, 1988
2. Ekmam L. Hansson E, Hau N. Carlsson E, Lundberg C: Toxicological studies on omeprazole. Scand J Gastroenterol. 108(Suppl): 56-69, 1985
3. Frantz JD, Betton G, Cartwright ME, Crissman JW, Macklin AW, Maronpot RR: Proliferative lesions of the non-glandular and glandular stomach in rats, GI-3. In: Guides for Toxicologic Pathology. STP/ARP/AFIP, Washington, DC. 1991
4. Hard GC, Iatropoulos NJ, Thake DC, Wheeler D, Tatematsu M, Hagiwara A, Williams GM, Wilson GE: Identity and pathogenesis of stomach tumors in Sprague-Dawley rats associated with the dietary administration of butachlor. Exp Toxic Pathol 47:95-105, 1995
5. Hirth RS, Evans LD, Buroker RA, Oleson FB: Gastric enterochromaffin-like cell hyperplasia and neoplasia in the rat: An indirect effect on the histamine H2-recptor antagonist, BL-6341. Tox Pathol 16(2):273-287, 1998
6. Thake DC, latropoulos NJ, Hard GC, Hotz KJ, Wang C-X, Williams GM, Wilson A: A study of the mechanism of butachlor-associated gastric neoplasms in Sprague-Dawley rats. Exp Toxic Pathol 47: 107-116, 1995
Case IV - 99-000174-9c, 9b, 9c, 9d, 9e (AFIP# 2694795)
Signalment: Two female B6,129 mice (C57BL/6 x 129) (Mus musculus), with targeted mutation (gene name pending), 7 and 8 months old.
History: Clinically normal in early phases, but eventually sicken and die from renal disease.
Gross Pathology: Kidneys are granular in appearance.
Laboratory Results: Urinalysis, blood parameters and ultrastructural studies are not available for these two mice.

Contributor's Diagnoses and Comments:
1. Acute proliferative glomerulonephritis in earliest stage.
2. Membranoproliferative glomerulonephritis in moderate stage.
3. Sclerosing glomerulonephritis at end stage.
4. Tubular casts.
5. Nephropathy.
Etiology - specific gene inactivation.
AFIP Diagnosis: Kidney: Glomerulonephritis, membranoproliferative, global, chronic, diffuse, moderate, with multifocal lymphoplasmacytic interstitial nephritis and tubular proteinosis, B6,129 (C57BL/6 x 129) (Mus musculus), mouse.
Conference Note: The etiology of most spontaneous cases of glomerulonephritis is unknown. Glomerular lesions are generally uncommon in mice, although certain strains have a higher incidence than others do. In particular, NZB x NZW F1 hybrid mice have an autoimmune glomerulonephritis with a histologic appearance that is very similar to the case presented in conference. This lesion is characterized by mesangial proliferation, deposition of PAS-positive material, and lymphoplasmacytic infiltrates.

The contributor (Dr. Ward, the moderator of the conference) noted that this case represents a targeted genetic mutation whose effects and nature are not completely understood. Affected mice develop a fatal, progressive glomerulonephropathy. A unique fibrillar material that is thought to be immunoglobulin is deposited in the renal interstitium. Ninety percent of females and 40 percent of males in this group of mice have circulating anti-DNA antibodies.

Contributor: National Cancer Institute, Frederick, MD
Seely JC: Kindey. In: Pathology of the Mouse, eds. Maronpot RR, Boorman GA, Gaul BW, pp221-213. Cashe Vally Press, Vienna, IL 1999
J Scot Estep, DVM
Captain, VC, USA
Registry of Veterinary Pathology*
Department of Veterinary Pathology
Armed Forces Institute of Pathology
(202)782-2615; DSN: 662-2615
* The American Veterinary Medical Association and the American College of Veterinary Pathologists are co-sponsors of the Registry of Veterinary Pathology. The C.L. Davis Foundation also provides substantial support for the Registry.
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