Spontaneous lesions of the mouse biliary tract

.J ‘AMP.

PATH. 1984. VOL. 94

263

INTRODUCTION

Published reports of spontaneous pathological changes in the murine biliar). tract are sparsr, probably because of its relatively infrequent examination. Sheldon and Greenman ( 1979) f ound a low incidence of single, small intramural cysts: Yang and Campbell (1964) described crystalline material in 6 mice with cholecystitis, and Cloudman (1941) reported papillomata. Reports of induced lesions of the mouse biliary tract are also infrequent. Tepperman, Caldwell and Tepperman (1964) induced gallstones and cholecvstitis with an atherogenic diet. Enomoto, Naoe, Harada, Miyata Saito and Goguchi ( 1974) produced marked proliferative and inflammatory changes and choleliths with a similar diet, and adenocarcinomata with 2-acetamidofluorene. Hyperplasia and hypertrophy of the extra-hepatic bile ducts \vere described after oestrogen administration by Gardner, Allen and Smith ( 194 I 1 and after transplantation of pituitary growths by Furth, Gadsden and Upton 1952). The present report describes a number of spontaneous lesions ohserved during the examination of tissues from 2400 mice from 4 life-span carcinogenicity studies. MATERIALS

AND

METHODS

A group of’ 2400 (equal numbers males and females) CD-l, SPF mice (Charles Kiver. Manston, Kent, England) from 4 carcinogenicity studies were maintained under strict barrier conditions for up to 120 weeks. A full range of tissues, including gall bladder and liver, was subjected to rout& histopathological examination. In those tissues of the biliary tract in which lesion5 were detected additional sections were stained with periodic-acid SchifT-Alcian blue .Mowry, 1963); high iron diamine-Alcian blue (Spicer, 1965); Gram’s stain; Giemsa’s stain, and Fouchet’s reaction. RESULTS

The lesions described in Table 1 were incidental findings ii-om 4 carcinogenicitv studies. As they showed no treatment-related trends and were all 01‘ low iniidence and as each was found in at least one untreated control animal, thr lesions were considered to be spontaneous in origin (Table 1). 1ll)2l-W75/84/020263

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Press Inc.. (Lundoni

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Glandular metaplasia Papillomatous hyperplasia Papilloma Epithelial ulceration Intra-mural cysts Cholecystitis lntra-hepatic bile ducts Glandular metaplasia Cholangitis Total mice examined * Not receiving

Glandular

potential

Metaplasia

I I 2 I I

2 I -~ 2 2 2

2

I

300

900

I 1 I

30:

900

carcinogens.

of the Gall Bladder

This condition occurred in 3 female mice and was always associated with choleliths. The stones were usually rectangular, occasionally needle-shaped and varied from strongly eosinophilic to almost translucent (Fig. 1). They were embedded in accumulations of both neutral and acid mucins. The gall bladder walls were thickened by fibrous tissue and the mucosa folded with crypts and mucous glands. Slight diffuse infiltrates of both acute and chronic inflammatory cells were present in the walls. The superficial epithelial cells were mostly columnar, some with a prominent homogeneous, strongly eosinophilic, cytoplasm (Fig. 1). Occasional goblet cells were also present in the epithelium and stained positively for acid mucin. In the submucosal glands (Fig. 2) the goblet cells contained predominantly non-sulphated acid mucin, but a few cells, particularly at the base of the glands, contained sulphated mucin. Occasional needle-shaped or rectangular choleliths were present in the gland lumina and crypts. The cystic duct and, to a lesser extent, the common bile duct showed similar metaplastic changes in one mouse. Gram and Giemsa stains were negative and no related hepatic lesions were present in any of the mice. Glandular- Metaplasia

of the Into-a-hepatic Bile Ducts

Marked hypertrophy and hyperplasia of the intra-hepatic biliary system were found in 3 female mice. The bile ducts had prominent mucosal folds and crypts with subepithelial mucous glands (Fig. 3). A few needle-shaped crystals were present in the lumina. The superficial epithelial cells were cuboidal to columnar, with prominent homogeneous, strongly eosinophilic cytoplasm (Fig. 4). Moderate mixed pericholangitis and periductal fibrosis were also present. The subepithelial glands contained acid-mucin-producing goblet cells. Giemsa, Gram and Fouchet stains were all negative. The common bile duct and gall bladders were unaffected, but in 2 cases the intra-pancreatic ducts demonstrated similar glandular metaplasia.

BILIARY

l‘iq. Fiq

I. Glandular metaplasia ha\.c a homogrnrous 2’. ~;landular meraplasia IllllC x 200.

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of the gall bladder. Rectangular choleliths cytoplasm. HE x 200. of’ the gall bladder. .4rid mucin strongly

embrddt-d rtainctl

in mucin. in the

~ianck

Epithclial

cell!

l’AS:~ll~~i.~~r

266

Fig. Fig.

D.

J.

LEWIS

3. Glandular metaplasia of an intra-hepatic bile duct. The duct is hypcrplastir, with folds, subepitheiial glands, and periductal fibrosis. Adjacent liver parenchyma is normal. HE x 200. 4. Glandular metaplasia of an intra-hepatic bile duct. Higher power of part of Fig. 3 showing homogeneous cytoplasm of epithelial cells, and subepithelial glands. HE x 500.

BILIARY

Papillomatoxr

flyperplasia

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and Papilloma oJ‘ the Gall Bladdu

A single papilloma was found in a male mouse and 2 female mice had a diffuse papillomatous hyperplasia (Fig. 5). In all cases, the epithelial cells were supported by a delicate interbranching stroma. The cells were cuboidal to columnar (Fig. 6) and slightly larger than those ofadjacent normal epithelium. Increased numbers of PAS-positive granules (neutral mucin) were present in the apical cytoplasm, but the cells were negative with Alcian blue and high iron diamine. Epithelial

lJ/ceration of the Gall Bladder

Small, usually single, foci of epithelial ulceration with underlying necrosis. fibrosis and acute inflammation were found in four female mice (Fig. 7). In addition, complete epithelial ulceration with marked fibrous thickening of the gall bladder wall was present in a single male mouse. The lumen was filled with necrotic, haemorrhagic debris. A slight mixed inflammatory cell infiltration and a few remnants of glandular structures were found in the wall. Gram and Giemsa stains were negative in all cases. /n&a-mural

CvstJ in the Gall Bladder

Variable numbers of small intra-mural cysts were found in 4 mice. In 3 f‘emale animals the cysts were lined by simple cuboidal epithelium with mucus in the lumina. A male mouse had a single squamous cyst and its lumen was filled by concentric keratin lamellae.

A slight degree of chronic pericholangitis and cholangitis was seen in man) of-the mice examined. However, in one male mouse moderate dilatation of the intra-hepatic bile ducts was associated with a marked degree of chronic cholangitis. The gall bladder and common bile duct were unaffected. C<‘holecy.c titis In addition to the various degrees of cholecystitis described in the previous lesions? 3 cases of acute inflammation associated with Gram-positive cocci occurred, all in female mice. A generalized slight epithelial hyperplasia was present in one case, but in the other mice the mucosa was slightly folded, with shallow crypts. Small clusters of goblet cells were found at the base of a few crypts. Most of these cells contained acid non-sulphated mucin, but a few stained positively with high iron diamine which indicated sulphated mucin. DISCUSSION

In man, metaplasia of the gall bladder may be either squamous or glandular (De Boer, Ma, Rees and Nayman, 1981). Laitio (1975, 1976) subdivided

268

Fig. 5. Papillomatous hyprrplasia HE x 200. Fig. 6. Papillomatous hypcrplasia of cpithelial cells is dark.

D. J.

of the gall hladder. of the gall bladder. The stroma contains

LEWIS

Delicate

stroma

supporting

columnar

epithelial

Higher power view of part of Fig. 5. Apical few cells. HE x 500.

cells

cytoplasm

BILIARY

LESIONS

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269

glandular metaptasia into intestinal, gastric body and antrat types. Jaarvi and I,aurcn ( 1967) defined intestinal glandular metaplasia as a condition in which the gall htadder mucosa transformed into a form of intestinal epithelium M.ith vntcroc‘ytes. goblet cells, Paneth cells and entcrochromaffin cells. De Boer P/ (I/. ( 1981 ; fbund glandular metaplasia in 3.5 per cent of‘surgicatty-rern~~~e~t gall htactders and ctemonstratect the presence of‘ intestine-associated antigens. 1,aitio i 1975) found that in cases of glandular mctaptasia the amount of Noel~utphatcd acid mucin increased. In most. if‘not all these puhtishect accounts. ~tandular metaplasia was associated with ~gattstoncs. Reports of‘ sponlant.ous glandular mrtaplasia have not been traced in the mouse. ‘I’hc 3 casts reporrcd hew were atw associated with chotetiths and with the production of prcttominantt\~ non-sulphatect acid mucin. In man. ,galtstoncs arc associated with ilic~reasccl mucin production. Lee (1981) has shown that mucus production t~recectcd gallstone formation in three difberent ammat modcts. an ;ttulost Glandular metaptasia of the intra-hcpatic bite ducts c~ausect iclcnticat reaction to ‘gall bladder metaplasia. This similarit)-- \,vas cmphasizcd t)>. the prescnc~ of‘cholelith-like crystals in the hepatic hitc ducts. The t&mation (c)f‘gallstones in intra-hepatic bite ducts is known to occur occasionatt\~ in man ; Montgomery, 196.5 i . The cause of gallstones has not hecn conc1usi;x.t) c,htat)lished but alterations in bite composition, stasis. infbction and inftammation are possible factors (Shore. 1966). No direct c\~iclencc wx4 ohtaincd from

270

D. J.

LEWIS

the present study, but the presence of cholecystitis, associated with Grampositive bacteria in some mice, may be relevant. In man, cholecystitis is usually associated with gallstones (Shore, 1966) ; the inflammation may be due either to the action of bile on the mucosa, or to bacterial infection. The presence of Gram-positive cocci in all cases observed in this study favours the latter. The route of infection by bacteria may be either ascending from the duodenum (Kelly, Baggott and Gaskell, 1975)) or systemic (McClure, Chapman, Hooper, Smith and Fletcher, 1978). Cholangitis is generally considered to arise as a result of partial or intermittent obstruction of bile ducts (Shore, 1966). Stagnant bile is* liable to ascending infections from the duodenum. The dilatation of the bile ducts supports an obstructional cause. Tumours of the gall bladder are rare in most species (McClure et al., 1978). Papillomata have been reported in the guinea-pig (Blumenthal and Rogers, 1966). Papillary adenomata are seldom recognized in domestic animals (Ponomarkov and Mackey, 1976) and true papilloma is a rare tumour in man (Shore, 1966). In the present study, diffuse lesions were termed hyperplasia, whereas a single more localized lesion was regarded as a papilloma. All the lesions described in this report were of low incidence, e.g. out of a population of 2400 mice, 3 had gall bladder glandular metaplasia, 3 had glandular metaplasia of the intra-hepatic bile ducts, and one had a papilloma. A distinct female predominance was noted for most lesions and glandular metaplasia and cholelithiasis were found exclusively in females. A similar higher female incidence is known to occur in man (Shore, 1966). SUMMARY

During the routine histological examination of 2400 aged mice from lifespan carcinogenicity studies a low prevalence of glandular metaplasia of the gall bladder and of the intra-hepatic bile ducts (all associated with cholelithiasis), cholecystitis, cholangitis, papillomatous hyperplasia, papilloma, intra-mural cysts, and focal epithelial ulceration was found. The lesions were found predominantly in female mice and were not treatment related.

REFERENCES

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oj’the Laboratog Inappropriate

mucin production in gall bladder metaplasia and neoplasia-an

immuno-

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