Spontaneous progressive nephropathy dominated by glomerular lesions in common marmosets has been reported. However, the histopathologic characteristics, including the relationship between glomerular and tubulointerstitial lesions, have not been described in detail. In the present study, the authors examined the histopathologic characteristics of the background renal lesions in common marmosets (3 males and 9 females, 3 to 8 years old). The severity of glomerular lesions was graded into 3 classes: grade I, no alteration; grade II, hilar/focal increase of mesangial matrix; grade III, global/diffuse increase of mesangial matrix. Tubulointerstitial lesions (tubular regeneration and hyperplasia and interstitial inflammation and fibrosis) were scored according to the area of each lesion. The renal lesions were characterized by enlargement of glomeruli, expanded mesangial area with increase of periodic acid-Schiff reaction-positive matrix, tubular regeneration and hyperplasia, and interstitial inflammation and fibrosis. Glomerular lesions progressed with increasing mesangial matrix and aging. Additionally, the tubulointerstitial lesions became exacerbated with progressing glomerular lesions. Tubular hyperplasia was divided into 4 types according to the structure of the cell layer (simple or stratified-like), the area of increased lining cells (partial or entire), cytoplasmic staining (eosinophilic or basophilic), brush border and thickness of basement membrane, and the activity of cell proliferation. In conclusion, the background renal lesions in common marmosets were characterized by glomerular lesions with increase of mesangial matrix, which progressed with aging, and secondary tubulointerstitial lesions, including tubular hyperplasia. Those lesions were thus diagnosed as progressive glomerulonephropathy in common marmosets.

Multicystic biliary hamartoma is a very rare hamartomatous nodule in the liver, which has recently been described as a new category of hepatic nodular lesion. We herein report the case of a 55-year-old man histopathologically diagnosed with this entity following surgery. A solitary multilocular lesion in the liver was pointed out by ultrasonography during a systemic examination for a positive HBs antigen. This nodule could not be definitively diagnosed by radiologic modalities, including computed tomography, magnetic resonance imaging and arteriography. The patient underwent a partial resection of the posterior segment of the liver. The nodule was a localized lesion which measured 5 x 3 cm at the widest point and displayed a honeycomb appearance. Histologically, it consisted of ductal structures, periductal glands, fibrous connective tissues containing blood vessels, and bile-like materials and xanthogranulomatous inflammation within some ducts. Liver parenchyma was not present in the nodule and the bile ducts were not dilated in the background liver. The ductal epithelium expressed biliary type cytokeratins (CK7 and 19) in immunohistochemical studies. These histopathological features were consistent with multicystic biliary hamartoma, and we discuss this rare case in detail in this report.