Hyperplastic and neoplastic lesions of the mammary gland in macaques.

Macaques provide an important animal model for the study of hormonal agents and their effects on risk biomarkers for breast cancer. A common criticism of this model is that spontaneous breast cancer has rarely been described in these animals. In this report, we characterize 35 mammary gland lesions ranging from ductal hyperplasia to carcinoma in situ and invasive ductal carcinoma in cynomolgus and rhesus macaques. Based on a retrospective analysis, we estimated the lifetime incidence of mammary gland neoplasia in aged female macaques to be about 6%. Hyperplastic lesions (n = 19) occurred segmentally along ducts and included such features as columnar alteration, micropapillary atypia, and fibroadenomatous change. In situ carcinomas (n = 8) included solid, comedo, cribriform, and micropapillary elements, encompassing 4 of the major architectural patterns seen in human lesions. Invasive ductal carcinomas (n = 8) were generally solid, with prominent central necrosis and mineralization, often on a background of micropapillary ductal hyperplasia and in situ carcinoma. Cytologic changes of invasive lesions included increased mitoses, nuclear pleomorphism, extensive microinvasion, and stromal desmoplasia. Axillary lymph-node metastases were confirmed in 5 of the 8 invasive carcinomas. On immunohistochemistry, intraductal and invasive carcinomas had increased Ki67/MIB1 and HER2 expression and selective loss of estrogen and progesterone receptors. These findings suggest that breast cancer is an underreported lesion in macaques and highlight unique morphologic and molecular similarities in breast cancer between human and macaque species.

Clinicopathologic analysis of HER-2/neu immunoexpression among various histologic subtypes and grades of osteosarcoma.

Overexpression of the HER-2/neu oncogene appears to have prognostic significance in breast cancer. Recently, some have reported a relationship between increased immunohistochemical expression in osteosarcoma and poor clinical outcome. Despite limited data, a pilot trial of Herceptin, which targets the oncogene product, has been initiated for the therapy of some metastatic osteosarcomas (CCG-P9852). Archival formalin-fixed, paraffin-embedded tissue obtained from 41 patients diagnosed with osteosarcoma was examined immunohistochemically by 2 antibodies against the HER-2/neu oncogene product: CB-11 (monoclonal, 1/100) and Oncor (polyclonal, 1/200). All but one tumor (case of recurrent dedifferentiated parosteal osteosarcoma) represented primary tumor samples; when applicable, only prechemotherapy biopsies were analyzed. The study sample included the full spectrum of histologic subtypes and grades of osteosarcoma (25 conventional high grade; 3 telangiectatic; 1 small cell; 6 parosteal; 1 periosteal; and 5 low-grade intramedullary). A case of metastatic breast cancer with known overexpression of the HER-2/neu oncogene served as the positive control. Complete membranous positivity, considered prognostically significant in breast cancer, was not seen in any of our osteosarcoma cases. At least focal cytoplasmic positivity was documented in 40 (98%) tumors using the CB11 antibody and in 34 (83%) using the Oncor antibody. The intensity of the cytoplasmic staining (0, 1-3+) did not correlate with histologic subtype/grade, response to chemotherapy (<90% versus > or = 90% necrosis), metastasis, or survival. Immunohistochemical overexpression of the HER-2/neu oncogene, defined as complete membranous positivity, is not present in our series of osteosarcomas. Cytoplasmic positivity is observed in most osteosarcomas, irrespective of histologic subtype/grade, and is not associated with response to preoperative chemotherapy or disease progression.

Prospective trial for the treatment of malignant peritoneal mesothelioma.

Malignant peritoneal mesothelioma (MPM) is a rare and often rapidly fatal disease with median survival of 5 to 12 months for untreated cases and 16 months reported after multimodality treatment. We report a prospective clinical treatment study using cytoreductive surgery combined with intraoperative intraperitoneal heated chemotherapy (IPHC) perfusion using mitomycin C for MPM. Twelve patients (11 male with a mean age 51 years) were treated. Seven patients presented with bulky disease and seven with ascites. All underwent exploratory laparotomy with histologically confirmed diagnosis of MPM. Surgical debulking as feasible was performed. Complete gross tumor removal was possible in only one patient. Cytoreduction was followed by a 2-hour closed low-volume IPHC using mitomycin C. One patient died 50 days postoperatively from complications relating to small bowel perforation. Hematologic toxicity of the procedure was minimal. Ascites was controlled in all patients and permanently in 86 per cent of patients presenting with ascites. To date median survival is 34.2 months with median follow-up of 45.2 months. One patient was re-explored for ventral hernia 2 years post-IPHC, had negative peritoneal biopsies, and remains disease-free at 5 years. Given the dismal prognosis associated with MPM the results of treatment with cytoreductive surgery combined with IPHC perfusion are encouraging. The rarity of MPM makes appropriately powered prospective randomized trials unlikely. Therefore, we now offer this approach off protocol; however, further study of this combined modality therapy is warranted.

Cytology of endolymphatic sac tumor.

A 77-year-old man presented with decreased mental status and an enhancing partially cystic tumor along the left tentorium on magnetic resonance imaging after mastoidectomy and petrosectomy for an "auditory canal tumor." Smears of the aspirated cyst fluid revealed rare epithelial cell clusters, some with papillary features, foamy macrophages, and blood. The cells were orderly, with fairly bland nuclei and well-defined cell borders. The cell block contained similar epithelium, with cells containing eosinophilic and focally vacuolated cytoplasm, some with pigmented granules resembling hemosiderin. Numerous foam cells were also present. Review of the patient's previous and concurrent resection material showed an endolymphatic sac tumor, a rare neoplasm that arises in the endolymphatic sac in the temporal bone. The previously undescribed cytologic features of this rare neoplasm are discussed.

Gelatinous ascites: a cytohistologic study of pseudomyxoma peritonei in 67 patients.

BACKGROUND: Pseudomyxoma peritonei (PMP) is a rare condition characterized by gelatinous ascites. Although the histologic attributes of PMP have been well studied, the cytologic features remain ill defined. METHODS: We reviewed the peritoneal washings (PW) in 67 patients with PMP to identify cytomorphologic features useful in classifying cases as either disseminated peritoneal adenomucinosis (DPAM) or peritoneal mucinous carcinomatosis (PMCA). Histologic specimens were correlated with the cytologic diagnoses. Correlation between cytologic diagnosis and patient outcome was investigated. RESULTS: Neoplastic epithelial cells were identified in 63 of 67 PW (94%). Concordance with the histologic diagnosis was obtained in 61 of 63 cases. Of these 36.5% were cytologically classified as DPAM with primary appendiceal neoplasms in 19 cases. Thirty-four of 63 cases (53.9%) were cytologically diagnosed as PMCA based on PW cytology. Most were of appendiceal or colonic origin. Four cases displayed cytologic features of both DPAM and PMCA. Two discordant cases each with a cytologic diagnosis of PMCA had an appendiceal adenoma. Acellular mucin alone was identified in the PW in four cases. Analysis of follow-up data revealed that cases diagnosed as DPAM had a better prognosis than those diagnosed as PMCA. CONCLUSIONS: Cytomorphologic features of epithelial cells in PW material can accurately categorize cases of PMP as either DPAM or PMCA. Furthermore, this categorization appears to have important prognostic implications.

Cytology of angiosarcoma. Findings in fourteen fine-needle aspiration biopsy specimens and one pleural fluid specimen.

We report the cytologic features of 15 cases of angiosarcoma from various sites and include 14 fine-needle aspiration (FNA) biopsy specimens and 1 pleural fluid specimen. Six were initial diagnoses with histologic confirmation; an additional case in the liver was an initial diagnosis without tissue confirmation. One case represented lymph node metastasis from a primary prostatic epithelioid angiosarcoma. In 10 cases, immunohistochemical staining for factor VIII-related antigen, CD34, CD31, or Ulex europaeus agglutinin I was performed on the cytology or histology specimen. The aspirates varied in cellularity, and the degree of nuclear atypia ranged from relatively bland in a case of low-grade angiosarcoma of the prostate to highly pleomorphic in a lymph node metastasis from a facial cutaneous angiosarcoma. Vasoformative features such as intracellular RBCs, well-formed vessels, attempts at microacinar/lumen formation, and intracytoplasmic lumens were variably present. The background was bloody in all specimens, with necrosis in rare cases. This cytologic series emphasizes that the cytologic features are heterogeneous but that the diagnosis can be suggested by fine-needle aspiration (FNA) when vasoformative features are present. The diagnosis can be made conclusively by FNA with immunocytochemical confirmation of endothelial differentiation.

Cytoreductive surgery with intraperitoneal hyperthermic chemotherapy for disseminated peritoneal cancer of gastrointestinal origin.

No standard effective treatment exists for peritoneal carcinomatosis of gastrointestinal origin. The pharmacokinetic advantage of intraperitoneal chemotherapy and the synergy of heat and certain anticancer agents have prompted researchers to investigate intraperitoneal hyperthermic chemotherapy in treating disseminated peritoneal cancers. We have conducted a large Phase II trial to determine the safety and efficacy of aggressive cytoreductive surgery and intraperitoneal hyperthermic chemotherapy (IPHC) in treating peritoneal carcinomatosis of gastrointestinal origin. Patients with disseminated peritoneal carcinomatosis of gastrointestinal origin with or without malignant ascites were eligible. After aggressive surgical debulking, patients were administered a 2-hour heated (40.5 degrees C) intraperitoneal perfusion with mitomycin C. The major response variable monitored was overall survival. Patients were assessed for toxicity after IPHC administration using the National Cancer Institute Common Toxicity Criteria. Eighty-four patients with peritoneal carcinomatosis of gastrointestinal origin were evaluated for survival and toxicity (colon, n = 38; appendix, n = 22; stomach, n = 19; other gastrointestinal, n = 5). Thirty-nine (46%) patients had malignant ascites at the time of therapy. The operative mortality (30-day) was 6 per cent. Hematologic toxicity was the most common toxicity but was of mild to moderate severity (7 and 4% of patients had grade 3/4 white blood cell or platelet toxicity, respectively). The overall median survival was 14.3 months. The median survival of patients with peritoneal carcinomatosis of appendiceal, colorectal, and gastric origins were 31.1+, 14.6, and 10.1 months, respectively. Significant differences in median survival were seen in patients without and with malignant ascites (27.7 vs 7.6 months; P = 0.0004) and R0/R1 (complete gross tumor resection) versus R2 (gross residual tumor) surgical resection status (28.5+ vs 10.8 months, P = 0.0002). These data suggest that aggressive cytoreductive surgery with IPHC using mitomycin C is safe and effective in treating peritoneal carcinomatosis of gastrointestinal origin. Additional studies and broader applications of this treatment are encouraged.

Diagnosis and subclassification of primary and recurrent lymphoma. The usefulness and limitations of combined fine-needle aspiration cytomorphology and flow cytometry.

The primary diagnosis of non-Hodgkin lymphoma/leukemia by fine-needle aspiration (FNA) is still controversial and relatively underused. We evaluated our FNA experience with lymphomas using the revised European-American classification of lymphoid neoplasms to determine the reliability of FNA when combined with flow cytometry in the diagnosis of lymphoma, the types of diagnoses made, and the limitations of this technique. Slides and reports from all lymph node and extranodal FNAs performed during the period January 1, 1993, to December 31, 1998, with a diagnosis of lymphoma or benign lymphoid process were reviewed. There were 290 aspirates from 275 patients. These included 158 cases of lymphoma, of which 86 (54.4%) were primary and 72 (45.6%) were recurrent. There were 44 aspirates suggestive of lymphoma and 81 benign/reactive diagnoses. With diagnoses suggestive of lymphoma considered as positive for lymphoma, levels of diagnostic sensitivity and specificity were 95% and 85%, respectively. Specificity was 100% when only definitive diagnoses of lymphoma were considered. Clearly, FNA and immunophenotyping by flow cytometry are complementary and obviate a more invasive open biopsy for many patients with lymphadenopathy.

The estrogen replacement and atherosclerosis (ERA) study: study design and baseline characteristics of the cohort.

The Estrogen Replacement and Atherosclerosis (ERA) trial is a three-arm, randomized, placebo-controlled, double-blind trial to evaluate the effects of estrogen replacement therapy (0.625 mg/day oral conjugated estrogen) with or without continuous low-dose progestin (2.5 mg oral medroxyprogesterone acetate/day) versus placebo on progression of atherosclerosis. A total of 309 postmenopausal women at five sites underwent baseline coronary angiography and were randomized. Participants will have repeat coronary angiography after an average of 3.25 years of treatment. The primary outcome of interest will be change in minimum diameter of the major epicardial segments, as assessed by quantitative coronary angiography. The primary aim is to test the hypothesis that either form of hormone therapy will slow the progression or induce regression of coronary atherosclerosis compared to placebo. The secondary aims are to assess the effects of the two treatments versus placebo on endothelial function (measured using flow-mediated vasodilator responses), on several presumed mediators of estrogen's effect on atherosclerosis (i.e., plasma lipids and lipoproteins, blood pressure, glucose metabolism, hemostatic factors, and antioxidant activity), on other factors that influence the development of coronary heart disease (i.e., diet, smoking status, exercise, weight, and health-related quality of life issues), and on clinical cardiovascular events. The ERA trial is the first angiographic endpoint clinical trial to examine the effects of postmenopausal hormone replacement on coronary atherosclerosis in women. It will provide an unparalleled opportunity to determine if either regimen of hormone therapy is effective in slowing the progress of angiographically defined coronary atherosclerosis. This study will complement other estrogen replacement trials, such as the PEPI, HERS, and Women's Health Initiative studies, to provide a more comprehensive examination of the effects of estrogen replacement on cardiovascular risk factors, anatomic and functional manifestations of atherosclerosis, and risk for coronary heart disease in postmenopausal women. Control Clin Trials 2000;21:257-285

The clinical application and cost analysis of fine-needle aspiration biopsy in the diagnosis of mass lesions in sarcoidosis.

BACKGROUND: Sarcoidosis is a prevalent disease of unknown cause characterized by granulomatous inflammation that often creates deep and/or superficial mass lesions. Tissue samples are considered the "gold standard" in diagnosis; however, it is a medically treated disease. We analyzed the utility and relative cost-effectiveness of fine-needle aspiration biopsy (FNAB) in the clinical investigation of patients with both suspected and unsuspected sarcoidosis. METHODS: All FNAB cases with sarcoidosis either as the cytologic diagnosis or mentioned as part of the differential diagnosis were retrospectively reviewed for clinical history, follow-up, cytologic features, and surgical pathology findings. Comparative analysis of cost of FNAB and excisional biopsy were also made. RESULTS: Thirty-two FNABs in 28 patients included 17 women and 11 men. Anatomic sites included lymph node (n = 17), lung (n = 5), salivary gland (n = 8), and liver (n = 2). Sarcoidosis had already been diagnosed or was a clinical consideration prior to FNAB in 14 cases. Chest radiograph showed abnormal findings in 19 cases. Angiotensin-converting enzyme (ACE) was measured in seven patients and was elevated in four. All aspirates showed granulomatous inflammation; in 22 patients, special stains or cultures for microorganisms were negative. Simultaneous or subsequent excisional biopsies confirmed the FNAB findings in 17 patients. Institutional ratios of excisional biopsy to FNAB in the diagnosis of sarcoidosis ranged from 4 to 19:1. The cost of FNAB was only 12.5 to 50% that of tissue biopsy. CONCLUSIONS: FNAB appears to be underutilized in the diagnosis of sarcoidosis. When used in conjunction with radiologic and laboratory data, FNAB may be a reliable and cost-effective method of diagnosis, especially in patients with an established diagnosis of sarcoidosis.

Cytomorphologic features of Merkel cell carcinoma in fine needle aspiration biopsies. A study of two atypical cases.

OBJECTIVE: To report atypical cytomorphologic features in fine needle aspiration biopsies (FNABs) from two cases of Merkel cell carcinoma (MCC), a primary neuroendocrine neoplasm of skin. STUDY DESIGN: Retrospective review of FNABs with histologic correlation from six patients with MCC and a report of findings from two whose smears showed atypical features. RESULTS: Typically the aspirates produce highly cellular smears of loosely clustered and individual, relatively monomorphic, small tumor cells with round to oval, regularly contoured nuclei. In two of our cases, the tumor cell nuclei exhibited a spectrum of pleomorphism ranging from moderately complex nuclear membranes with cleaves, indentations and protrusions in one case to large, markedly bizarre, convoluted nuclei and multinucleate tumor cells in the extreme case. Both cases were primary neoplasms, and the diagnosis was based on clinical, histologic and immunohistochemical data. Additionally, electron microscopy was performed on the tumor with bizarre nuclei and demonstrated rare, dense core neurosecretory granules and paranuclear bundles of intermediate filaments.

The cytomorphology of pleuropulmonary blastoma.

Pleuropulmonary blastoma is a rare, primitive primary neoplasm of the thorax in young children. The tumor, which is often but not always associated with cystic lung lesions, may arise in pulmonary parenchyma, the mediastinum, and pleura. Histologically, it is characterized by a biphasic neoplastic population of undifferentiated-appearing small round cells and larger spindle-shaped cells. A proportion of these cancers may also manifest more specific mesenchymal differentiation. In contrast to the pulmonary blastoma of adults, a malignant epithelial component does not occur. We present herein the third known case of a fine needle aspiration biopsy of a pleuropulmonary blastoma in a 5-year-old girl. The smears were moderately cellular and included an admixture of the characteristic small ovoid blastemal elements and scattered spindled mesenchymal tumor cells.

Sentinel lymph node mapping for carcinoma of the colon: a pilot study.

Sentinel lymph node (SLN) mapping has evolved into the standard of care for melanoma and may replace routine node dissection in the treatment of breast cancer. There are few data evaluating sentinel node mapping in patients with cancer of the colon. This trial represents our initial experience with SLN mapping for carcinoma of the colon. SLN mapping was performed in 22 patients most of whom had biopsy-proven adenocarcinoma of the colon. One milliliter of isosulfan blue was injected with a 25-gauge needle into the subserosa at four sites around the edge of the palpable tumor. The SLN was identified visually and excised. A standard lymphadenectomy was then performed. The SLN was analyzed with standard hematoxylin and eosin evaluation. Immunohistochemical techniques for carcinoembryonic antigen and cytokeratin (Imm) were performed if the H&E was negative. The mapping added approximately 5 minutes to the total operative time and no adverse reactions to the dye occurred. A SLN was identified in 20 of 22 cases. In cases with negative lymph nodes the SLN was predictive of all the regional nodes by both H&E and Imm (14 of 14). In patients with positive lymph nodes the SLN was predictive in all cases (six of six). In one case the only node with disease was the SLN, and in this case the diease was identified by only Imm; thus this patient was upstaged. SLN mapping is feasible and safe and can readily be performed in patients with colonic cancer. In conjunction with SLN mapping, Imm techniques may upstage a subset of patients likely to be at increased risk for metastatic disease. Consequently SLN mapping of colon cancer should be evaluated in large prospective trials.

The role of fine-needle aspiration cytology in the evaluation of metastatic clear cell tumors.

BACKGROUND: Clear cell tumors (CCTs) occur as primary neoplasms in a number of anatomic sites. Due to their overlapping morphologic features, these tumors can be challenging for the cytologist, particularly when they present as metastatic lesions. METHODS: Forty-nine fine-needle aspirations (FNA) of metastatic CCTs from 46 patients (age range, 29-87 years; mean, 64 years) were reviewed retrospectively. In addition to the routine smears and cell block preparations, ancillary studies were performed in selected cases. Clinical and/or histologic follow-up was obtained for all patients. RESULTS: The sites of the 49 FNAs were the lung (12 cases), lymph nodes (9 cases), liver (7 cases), bone (7 cases), soft tissue (4 cases), pelvis (2 cases), adrenal gland (2 cases), pancreas (1 case), thyroid (2 cases), peritoneum (2 cases), and vagina (1 case). Twenty-seven patients had a previous history of a CCT and the FNA material in these cases was consistent with a metastasis. The primary anatomic sites in these cases were the kidney (20 cases), ovary (2 cases), salivary gland (1 case), and cervix (1 case). On light microscopy, these tumors had a similar appearance and often were indistinguishable. Nineteen patients did not have a prior history of malignancy; 12 of these patients had a concurrent renal mass and the diagnosis of metastatic renal cell carcinoma was made. The anatomic site of origin of seven of the ten remaining tumors (kidney [2 cases], lung [2 cases], ovary [1 case], germ cell [1 case], and endometrium [1 case]) was established through immunocytochemical studies of cytologic material and clinical follow-up. CONCLUSIONS: FNA plays an important role in the diagnosis of metastatic CCT. Cytologic examination, ancillary studies, and clinical information can establish the anatomic site of origin in the majority (95%) of cases, precluding the necessity of obtaining additional tissue. Cancer (Cancer Cytopathol)

Cytology of primary pulmonary mucoepidermoid and adenoid cystic carcinoma. A report of four cases.

BACKGROUND: Mucoepidermoid and adenoid cystic carcinomas are very rare primary pulmonary neoplasms that can be classified under the broader heading of salivary gland-like neoplasms (SGN). Both entities need to be considered in the cytologic differential diagnosis of lung tumors. We reviewed cytologic findings in primary pulmonary neoplasms diagnosed at our institution during the time period 1981 to the present along with outside consultation cases. CASES: Three cases of primary mucoepidermoid carcinoma and one case of primary adenoid cystic carcinoma of the lung were diagnosed based on cytology during the period examined. Patient ages were 16, 25, 47 and 78 years, respectively. The mucoepidermoid cytology specimens were composed of three cell types, mucinous, squamous and intermediate cells, at times associated with extracellular mucin. The adenoid cystic carcinoma consisted of small, uniform cells with dark nuclei, scant cytoplasm and associated, acellular balls of basement membrane material. CONCLUSION: The differential diagnosis for primary pulmonary neoplasms needs to include the rare SGN. Cytologic features of adenoid cystic carcinoma are diagnostic; those of mucoepidermoid carcinoma are at least suggestive.

Interobserver variability of a Papanicolaou smear diagnosis of atypical glandular cells of undetermined significance.

The interobserver variability of a Papanicolaou smear diagnosis of atypical glandular cells of undetermined significance (AGUS) has not been measured. Four expert cytopathologists retrospectively reclassified 100 smears originally diagnosed as AGUS; on follow-up examination, 54 had a clinically significant lesion and 46 had a benign lesion. The mean sensitivity and specificity of reclassification were 86% and 21%, respectively. The kappa statistic for pairwise cytopathologist comparison varied from 0.16 to 0.27. In 45% of cases the cytopathologists all used different Bethesda System diagnoses, and in no case did all the cytopathologists use the same diagnosis. There was little agreement on which cytologic criteria were important in separating clinically significant and benign lesions. We conclude the following: interobserver agreement in reclassifying AGUS lesions is very poor; the AGUS category is poorly understood, and there is no agreement on diagnostic cytologic criteria; and when reclassifying slides, cytopathologists make a number of false-negative diagnoses.

Histopathologic practices for esophageal biopsy specimens: survey results and implications for surveillance in patients with Barrett's esophagus.

A clinically valuable interpretation of esophageal biopsy specimens begins with well-prepared histologic sections. This may be especially true for reflux esophagitis and Barrett's glandular dysplasia. To determine exactly which histologic procedures are used by experts in gastrointestinal pathology, a checklist survey was mailed to 50 members of the Gastrointestinal Pathology Society. Responses were received from 42 (84%). Formalin, used 80% of the time, is overwhelmingly the most popular fixative. Orientation of biopsy material before further processing is performed in 36% of the institutions, most often (53%) by an endoscopy technician. The most frequently used (60%) substrate for orientation is filter material. The most common (83%) routine procedure uses only H&E staining. Others routinely add a mucin reaction to the H&E. Eleven different practices for sectioning are used; the most common (43%) is serial step sectioning at 3 levels. One third of the responders had a formal surveillance program for patients with Barrett's esophagus. For esophageal biopsy specimens, a broad spectrum of histologic practices exists. Trends for the more complex histotechnologic procedures to be used by those involved in screening for dysplastic Barrett's epithelium are evident.

Experimental study of acid burden and acute oesophagitis.

BACKGROUND: The relationship of the pH of oesophageal refluxate and its pepsin content to injury of oesophageal mucosa remains unclear. A study was made of the earliest morphological alterations in the oesophageal mucosa secondary to varying concentrations of hydrochloric acid with or without pepsin. METHODS: Adult cats had varying concentrations of acid with and without 1 per cent porcine pepsin infused into the oesophagus through a paediatric feeding tube placed 5 cm above the oesophagogastric junction at a rate of 1 ml/min for 30 min. At autopsy 24 h later, the oesophagus was removed intact and scored by an expanded modification of a previously published histopathological scoring system. This included estimates of the intensity and distribution of four morphological features: basal cell hyperplasia (BCH), intraepithelial leucocytes (IELs), subepithelial leucocytes and ulcers. Each of these four categories was scored from 0 to 4, with a maximum injury score of 16. RESULTS: Mean(s.e.m.) scores were as follows: pH 1, 15.0(1.0); pH 1 with pepsin, 13.3(1.4); pH 2, 15.3(0.7); pH 2 with pepsin, 11.7(1.1); pH 3, 1.8(1.6); pH 3 with pepsin, 3.7(1.9); pH 4 with or without pepsin, 0.6(0.2). Differences between pH 3 and 4 versus pH 1 and 2 were significant (P < 0.05). CONCLUSION: Injury to the oesophagus is more dependent on the pH of refluxate than on the presence of pepsin. Peptic injury appears to occur at a critical threshold of acid burden (pH < 3) as opposed to a graded level of injury based on a pH scale.