J. clin. Path., 1970, 23, 472-474

Tubular metaplasia in Bowman's capsule

A. MILFORD WARDFrom the Department ofPathology, University of Sheffield

SYNOPSIS Proximal tubular type metaplasia of the epithelium of Bowman's capsule isdescribed in a fit young adult male. This form of metaplasia is unlike those previously describedand could cause initial confusion if encountered in a percutaneous renal biopsy.

The upper part of the nephron can be divided intothe renal corpuscle, or Bowman's capsule, theneck portion, and the proximal tubule (Rouiller,1969). In man Bowman's capsule is lined by aninconspicuous layer of flattened squamous cells(Allen, 1962; Brewer, 1964; Heptinstall, 1967); inthe mink and mouse the parietal capsularepithelium is cuboidal (Crabtree, 1940; Rouiller,1969). The neck portion, seen in lower animals butnot in man, is lined by an epithelium which hasthe cytological characteristics of the proximaltubule (DuBois, 1969). Two types of metaplasiaof the capsular epithelium have been described, anadenomatoid type (Eisen, 1946; Chappell andPhillips, 1950; Nachman, 1962; Macpherson,1963) and a columnar type (Lloyd Thomas,1953; Finckh and Joske, 1954). A third variety isnow described.

epithelium is usually situated opposite to thevascular pole of the glomerular tuft, but mayextend around much of the capsule (Figs. l and 2).The cells have regular nuclei situated towards thebasal pole of the cell, and an eosinophilic cyto-plasm. Some cells show some basal striation,whilst all show a prominent brush border whichstains intensely with the periodic-acid-Schiff(PAS) method. The cytological characteristics areidentical to those of the neighbouring proximaltubular epithelial cells. In some glomeruli directcontinuity can be demonstrated between theproximal tubular epithelium and the metaplasticepithelium of Bowman's capsule (Figs. 3 and 4).No other abnormalities were detected in thekidney.

Discussion

Case Report

A fit young adult male (aged 19) died frommultiple injuries sustained in a road trafficaccident. Necropsy revealed no evidence of pre-existing disease. The kidneys were of normal size,weight, and texture.

HISTOPATHOLOGYTwenty-five per cent of the glomeruli show a highcuboidal epithelium replacing the normal flattenedepithelium of Bowman's capsule. The cuboidalReceived for publication 19 January 1970.

Instances of metaplasia of the capsular epitheliumare reported rarely in the literature, and one mustassume that this is an uncommon finding. The twotypes so far described differ on cytological andclinical grounds (Table).The adenomatoid type (Eisen, 1946) occurs in

both sexes and at varying ages. All patients haveadvanced, disseminated malignancy, usually in-volving the liver. The columnar type (Lloyd-Thomas, 1953)occursin both sexes but all patientsare under 25 years. No patient in this group hadany evidence of malignant disease, although fourhad diabetes (Finckh and Joske, 1954).The present case, representing a third variety of

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Tubular metaplasia in Bowman's capsule

Fig. 1 Glomerulus showing prominent tubular Fig. 2 Tubular metaplasia with prominent brushmetaplasia of the capsular epithelium opposite the border. Periodic acid Schiff x 125.vascular pole of the glomerulus. Haematoxylin andeosin x 125.

Fig. 3 Glomerulus showing continuity between Fig. 4 Glomerulus showing continuity betweenmetaplastic capsular epithelium and tubular epithelium. metaplastic capsular epithelium and tubular epithelium.Haematoxylin and eosin x 125. Note the prominent capsulo-tubular junction.

PAS x 125.

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474 A. Milford Ward

Case AuthorAdenomatoid typeAdenomatoid type

1 Eisen (1946)

2 Chappell & Phillips (1950)

3 Nachman (1962)

4 Macpherson (1963)

Columnar type5 Lloyd-Thomas (1953)6 Finckh & Joske (1954)

7 Finckh & Joske (1954)

8 Finckh & Joske (1954)

9 Finckh & Joske (1954)

10 Finckh & Joske (1954)

Tubular type11 Present case

Table Two types ofepithelium

Sex Age Comment

F 54 Metastatic carcinomagallbladder

M 16 Metastatic carcinomaadrenal

F 6/12 Metastatic carcinomaliver

F 74 Metastatic carcinoma(?) breast

FM

M

M

F

F

1414

15

16

16

25

Type II nephritisDiabetes: no evidenceof renal diseaseDiabetes: no evidenceof renal diseaseDiabetes: no evidenceof renal diseaseDiabetes: no evidenceof renal disease?Systematic lupus: noevidence of renaldisease

M 19 No evidence of renaldisease

metaplasia of the capsular

metaplasia of the capsular epithelium, has featuresin common with the columnar type, with theexception of the prominence of the cytologicalfeatures of proximal tubular epithelium. It seems

unlikely that this feature would have been over-looked in the case described by Lloyd-Thomas(1953) as the PAS method was used to demon-strate the basement membrane thickening oftype II nephritis.The aetiology of this lesion is obscure. Finckh

and Joske (1954) suggested persistence of somefoetal structure or potentiality, but neithercolumnar nor tubular change is seen in foetal or

neonatal material. It is possible that it represents amaldevelopment of the renal corpuscle and thatthe upper part of the proximal tubules has had to

dilate to accommodate the glomerular tuft. If thiswere the case, one would expect some evidence ofincompetence of the capsulo-tubular junction withprolapse of the glomerular tuft. This is not seen,although Finckh and Joske (1954) did note thisfeature once in one patient. Figures 3 and 4emphasize the competence of the capsulo-tubularjunction in this patient.The adenomatoid metaplasia described by

Eisen (1946) may well have a different aetiology.The lesion appears to have no pathological

significance.

I wish to thank Dr H. H. Pilling, H.M. Coronerfor the City of Sheffield and the West Riding ofYorkshire, Rotherham Division, for permission topublish details of this case.

References

Allen, A. C. (1962). The Kidney, 2nd ed., p. 34. Churchill,London.

Brewer, D. B. (1964). Renal Biopsy, p. 10. Arnold, London.Chappell, R. H., and Phillips, J. R. (1950). Adenomatoid changes

of renal glomerular capsular epithelium associated withadrenal tumor. Arch. Path., 49, 70-72.

Crabtree, C. (1940). Sex differences in the structure of Bowman'scapsule in the mouse. Science, 91, 299.

DuBois, A. M. (1969). In The Kidney, edited by C. Rouiller andA. F. Muller, vol. I, p. 29. Academic Press, New York& London.

Eisen, H. N. (1946). Adenomatoid transformation of the glomeru-lar capsular epithelium. Amer. J. Path., 22, 597-601.

Finckh, E. S., and Joske, R. A. (1954). The occurrence ofcolumnarepithelium in Bowman's capsule. J. Path. Bact., 68, 646-648.

Heptinstall, R. H. (1967). Pathology of the Kidney, p. 20.Churchill, London.

Lloyd-Thomas, H. G. L. (1953). Type 2 nephritis relapsing 30years after onset, with 2 full-term pregnancies occurringduring the course of the disease. Proc. roy. Soc. Med., 46,715-716.

Macpherson, D. J. (1963). Metaplasia of renal glom2rula rcapsularepithelium. J. clin. Path., 16, 220-222.

Nachman, R. L. (1962) Metaplasia of parietal capsular epitheliumof renal glomtrulus. Arch. Path., 73, 48-52.

Rouiller, C. (1969). In The Kidney edited by C. Rouillerand A. F. Muller, vol. 1, p. 74. Academic Press, NewYork & London.

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