Fred G. Silva

Primary Melanocytic Schwannoma of the Stomach Evidence of Dual Melanocytic and Schwannian Differentiation in an Extra-Axial Site in a Patient Without Neurofibromatosis

Pigmented neoplasms of the peripheral nervous system are uncommon. Such lesions, while well documented in the para‐axial region, are infrequently encountered in more peripheral extra‐axial sites. The authors present a case of a melanocytic schwannoma arising in the gastric antrum of a 51‐yearold woman. Ultrastructural features attesting to the nerve sheath origin of the neoplasm included the presence of a well‐developed basal lamina, complex infoldings of the plasma membrane, and intercellular bundles of long spaced collagen (“Luse bodies”). Premelanosomes and melanosomes in all stages of development were identified within the cytoplasm of many of the neoplastic cells, providing morphologic support for a close relationship between Schwann cells and melanocytes. Immunoperoxidase studies with S‐100 protein disclosed intense cytoplasmic staining throughout the tumor. The S‐100 protein antigen has been documented in both nerve sheath elements and melanocytes; this shared antigenicity lends further support to the close relationship between melanocytic and schwannian elements suggested by ultrastructural observations. Additional immunoperoxidase studies employing antibody to glial fibrillary acidic protein revealed focal cytoplasmic staining, an uncommon phenomenon in peripheral nerve sheath neoplasms. A review of the literature failed to provide any previous well documented cases of melanocytic schwannoma of the stomach. The patient was treated with en bloc resection of the tumor and gastric antrum, and was free of evidence of recurrent or metastatic disease 22 months postoperatively. Theories regarding the histogenesis of pigmented nerve sheath neoplasms and prognostic implications are discussed, based on experience with this and previously reported pigmented nerve sheath tumors.

Acute Tubulointerstitial Nephritis in Children: Clinical, Morphologic, and Lectin Studies: A Report of the Southwest Pediatric Nephrology Study Group

Clinical histories and renal biopsies were reviewed in 12 children with acute tubulointerstitial nephritis, which was drug related in eight, idiopathic in one, and multifactorial in three. Presentation with rashes and hypertension was most common in patients with drug-associated nephritis. Eosinophils, which were present in the majority of the renal biopsies, did not distinguish between drug-related and non-drug-related disease. The majority of the children had a good outcome irrespective of the insulting agent. Frequent tubular basement membrane breaks were identified in seven of the biopsies but were not associated with a poor outcome. Proximal tubule brush border thinning, demonstrated by periodic acid-Schiff and Tetragonolobus lotus staining, paralleled the severity of acute renal failure. Lectin and immunohistochemical techniques to identify proximal tubules (Tetragonolobus lotus), thick ascending limb of Henle (anti-Tamm-Horsfall protein antibodies), and collecting ducts (Arachis hypogaea) allowed better delineation of sites of inflammation and injury, showed collecting tubules to be involved in all cases, and demonstrated that small atrophic tubules were able to maintain the ability to stain with the appropriate lectin/antibody. It is proposed that studies using these techniques may better identify the nephron sites involved in a variety of renal diseases involving tubular segments.

Acute Interstitial Nephritis due to Amoxicillin Therapy

Acute interstitial nephritis (AIN) has been reported in association with therapy with a number of drugs. We report a patient who developed drug-related AIN while receiving intravenous amoxicillin therapy. The patient developed rash, secondary temperature elevation, and eosinophilia in association with nonoliguric renal failure. Renal biopsy showed evidence for AIN and the renal failure was responsive to corticosteroid therapy. AIN may occur in patients receiving any drug of the penicillin class. This reversible form of acute renal failure must not be overlooked in patients with other forms of renal disease.

Gastrin-secreting tumor of the duodenum (G-cell apudoma, associated with secondary biliary cirrhosis

A middle‐aged woman with evidence of chronic cholestasis of several years and no previous abdominal surgery was initially thought to have primary biliary cirrhosis. Clinical evaluation disclosed a well‐developed secondary biliary cirrhosis apparently caused by extrahepatic obstruction due to a 1 × 2 cm neoplasm of the periampullary duodenum. Electron microscopy and immunofluorescent studies showed the neoplasm to be a G‐cell adenoma. Wide local excision has resolved the biliary obstruction. Benign or slow‐growing duodenal tumors, if they involve the ampulla of Vater, may produce prolonged partial extrahepatic obstruction and secondary biliary cirrhosis.

Effect of unilateral nephrectomy on three patients with histopathological evidence of diabetic glomerulosclerosis in the resected kidney

Diabetes mellitus and surgical ablation of renal tissue are two independent influences associated with hyperfiltration and elevated levels of the glomerular transcapillary hydraulic pressure differential (delta P). There is increasing evidence that hyperfiltration with elevated delta P is pathogenic and leads to glomerular damage. The authors questioned whether these two influences (surgical ablation of renal tissue and diabetes mellitus) would act in an additive fashion in human patients to produce an accelerated decline in renal function. Three patients with non-insulin-dependent diabetes mellitus who had undergone a unilateral nephrectomy (for a variety of reasons) were (retrospectively) identified. In each patient, morphologic evidence of diabetic glomerulonephropathy was present in the resected kidney. The charts from these patients were reviewed and post-nephrectomy renal function was estimated over time by plotting reciprocal serum creatine values versus time. Follow-up intervals after nephrectomy varied from 4 to 15 years. The results of our follow-up showed no obvious detrimental effect on renal function (as measured by 1/serum creatinine) attributable to the unilateral nephrectomy. The authors conclude that residual renal function (and ultimate outcome) in patients with non-insulin-dependent diabetes mellitus is highly variable, but does not seem to be adversely affected (at least over the time span of observation in these patients) by unilateral nephrectomy.

Renal Lesions in Chronic Pancreatitis

Many patients with chronic pancreatitis (CP), even in the absence of intrinsic renal disease, are found to have abnormal urine, with persistent proteinuria, cylindruria, microhematuria and leukocyturia. The kidneys of 12 necropsy cases with CP showed mild to moderate arterial and arteriolar nephrosclerosis and no other significant changes. Renal biopsies were performed in 10 patients with CP without evidence of systemic disease or intrinsic renal disease, but with persistent urinary abnormalities. By light microscopy, mild arterial and arteriolar nephrosclerosis was present in 5 instances. In 1 patient, evidence of the reparative phase of acute tubular necrosis was noted. In 5 biopsies, electron microscopy revealed minimal to mild increase in mesangial matrix. Mild thickening of the glomerular basement membrane (GBM) was found in three instances but there was no clear-cut evidence of diabetic glomerulosclerosis. The presence of subendothelial electron-lucent material in 3 cases suggests the possibility of previous subclinical episodes of intravascular coagulation. The most consistent finding was the presence of lipid material in the cytoplasm of glomerular and tubular cells. The renal lesions associated with CP are mild, nonspecific and nonprogressive. Various pathogenetic factors can be invoked to account for their presence and for the urinary abnormalities found in patients with CP.