Quantitative CT evaluation of adrenal gland masses: a step forward in the differentiation between adenomas and nonadenomas?

PURPOSE: To assess the attenuation of the adrenal gland with computed tomography (CT) before and after multiple phases of contrast enhancement in both control subjects and patients with adenomas and nonadenomas. MATERIALS AND METHODS: Seventy-two patients with 78 adrenal masses (41 adenomas, 37 nonadenomas) underwent helical CT. Forty subjects served as controls. Unenhanced CT was performed followed by enhanced CT at 30, 60, 90, and 180 seconds and 30 minutes. RESULTS: At unenhanced CT, mean attenuation was 4 HU +/- 16 for adenomas compared with 37 HU +/- 12 for the nonadenomas (P < .001) and 24 HU +/- 3 for normal glands. Although the mean attenuation of nonademonas was significantly greater than that of adenomas on 60- and 90-second scans (P < .001), there was greater overlap in attenuation of the adenomas and nonadenomas than on unenhanced images. At 180 seconds, nonadenomas had higher attenuation than adenomas (73 HU +/- 17 vs 41 HU +/- 18; P < .001). At 30 minutes, all adenomas had attenuation less than 37 HU, whereas all nonadenomas had attenuation greater than 41 HU. CONCLUSION: Delayed-enhanced CT scans obtained 30 minutes after administration of contrast material can enable differentiation of adenomas and nonadenomas.     

Quantitative evaluation of pancreatic enhancement during dual-phase helical CT

PURPOSE: To determine the improvement in pancreatic enhancement at helical computed tomography (CT) performed with an early delay after administration of contrast material compared with that performed with a standard delay. MATERIALS AND METHODS: Dual-phase helical CT of the abdomen was performed in 120 patients with a 150-mL bolus of contrast material infused at 5 mL/sec. Early and standard delayed scanning was performed beginning at 20 seconds and 49-71 seconds, respectively. Regions of interest were measured in the head, body, and tail of the pancreas in 92 patients. The difference in enhancement between early and standard delayed scanning was calculated. RESULTS: Mean pancreatic enhancement was 82 HU +/- 3 (standard error) with an early delay, whereas enhancement on standard delay scans was 62 HU +/- 2 (P < .001). An improvement in enhancement greater than 10 HU was attained in 66 of 92 cases (72%). CONCLUSION: Pancreatic enhancement at helical CT with an early delay after contrast material administration is often significantly greater than the enhancement seen with a standard delay when a monophasic, rapidly infused bolus of contrast material is used.     

Ultrasonographic diagnosis of the parotid gland tumors--experience with 310 patients

The diagnostic value of ultrasonography of parotid gland tumors is to determine if the tumor is benign or malignant. In the period from 1984 to 1995, ultrasound examinations were performed on 310 patients with a space-occupying lesion of the parotid gland, using real time 3.75 MHz, 5 MHz and 7.5 MHz transducers. From a histological standpoint, there were 246 benign tumors, namely 144 pleomorphic adenomas, 35 adenolymphomas, 23 other adenomas, 14 cysts, 9 neurinomas, 3 lymphomas, 9 hemangiomas, 3 lymphangiomas and 6 lymph nodes. Another 64 were malignant tumors, namely, 7 mucoepidermoid carcinomas, 7 acinic cell carcinomas, 7 adenoid cystic carcinomas, 15 adenocarcinomas, 7 squamous cell carcinomas, 4 undifferentiated carcinomas, 10 carcinomas in pleomorphic adenoma, 3 malignant lymphomas, 2 metastatic carcinomas and 2 other carcinomas. According to our criteria for ultrasonographic diagnosis of the parotid gland tumors, the benign or malignant pattern was determined by the following findings; shape, boundary echo, internal echo and posterior echo. But in some cases we could not differentiate the two echogram patterns, and we call them the intermediate pattern. The total accuracy rate of the diagnosis of the 310 patients was 79.0%. (The intermediated pattern was found in 39 patients and these cases were considered to be misinterpreted.) In 268 primary parotid gland tumors (210 benign and 58 malignant tumors) excluding recurrent cases, lymph nodes, hemangiomas and so on, the sensitivity was 62.1%, the specificity was 91.4% and the total accuracy rate was 85.1%. The accuracy of sonography in determining whether a tumor was benign or malignant was affected by the tumor size; tumors smaller than 2 cm in diameter showed a tendency to be diagnosed as benign and tumors larger than 6 cm in diameter as malignant. In the 268 cases, the importance of the pattern of the boundary echo and the internal echo in differentiating benign and malignant tumors was examined retrospectively. In the 210 primary benign tumors, the benignity of the tumors was assessed correctly in 84.3% by the boundary echo and 85.7% by the internal echo. In the 58 primary malignant tumors, the malignancy was assessed correctly in 58.6% by the boundary echo and 43.1% by the internal echo. Strong echos, which are the signs of a malignant pattern, were seen in 14.8% of the benign tumors, and in 51.7% of the malignant tumors. It can be concluded that ultrasonography is very reliable for the examination of parotid gland tumors.     

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INTRODUCTION: High-resolution computed tomography (HRCT) with iodinated contrast material has been used by many authors to study solitary pulmonary nodules (SPNs). The degree of enhancement was correlated with the nodule malignancy. MATERIAL AND METHODS: Forty adult patients were examined, before and after contrast agent administration, with incremental dynamic CT. We selected 22 patients with SPNs (3-30 mm phi, except one with 40 mm phi). The CT numbers of the inner nodule were calculated before and 1, 2 and 3 minutes after the i.v. administration of a weight-related dose (1.5 mL/kg/min) of nonionic iodinated contrast agent. A dose of 100 mL contrast agent was used in the first 6 patients. The difference in CT numbers between unenhanced images and the images with maximum enhancement (max. attenuation) was also calculated. RESULTS: Histologic diagnoses included 4 tuberculomas, 3 hamartomas and 15 malignant tumors (9 adenocarcinomas, 5 squamous cell carcinomas and 1 non-Hodgkin lymphoma). The CT numbers (in Hounsfield units, HU) of malignant nodules ranged 12-31 HU (mean: 21.5 HU) before contrast agent administration; the "long-standing" tuberculomas ranged 11-22 HU (mean: 16.5 HU) and the hamartomas had a mean density of 10.5 HU. We excluded for the study two "fresh" tuberculomas, one of which was surrounded by a low-attenuation infiltrate (the halo sign). We selected a threshold value of 20 HU on enhanced CT images to distinguish malignant (> or = 20 HU) from benign (< or = 20 HU) nodules. All lung cancers had complete enhancement (mean density: 35.5 HU). With 20 HU as the threshold value for a positive test, sensitivity was 100%, specificity 85.7%, positive predictive value 93.8% and negative predictive value 100%; test bias was 1.067. CONCLUSION: Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-D glucose is reported to be as accurate as enhanced HRCT, but it does not provide accurate morphological information, is not widely available and it is quite expensive: therefore, in our opinion, CT should be preferred. After examining over 100 patients, we may use our results in the decision analysis comparing surgical risk with cancer risk.     

Plasma levels of amyloid beta proteins Abeta1-40 and Abeta1-42(43) are elevated in Down''s syndrome

We report a case of pseudosarcomatous fibromyxoid tumor of the bladder in a 23-year-old man with a 2 month history of painless gross hematuria, which was studied by biphasic contrast-enhanced helical CT. CT demonstrated a 2 cm diameter polypoid enhancing mass in the anterior bladder wall. The lesion measured 103 and 91 HU on early and delayed images, respectively. Increased contrast enhancement was attributed to a histologically highly vascular myxoid stroma.     

The accuracy of CT and MR evaluation of the sella turcica for detection of adrenocorticotropic hormone-secreting adenomas in Cushing disease

PURPOSE: To document the accuracy of CT and MR of the sella turcica for detecting adrenocorticotropic hormone-secreting adenomas in Cushing disease. METHODS: The radiologic findings of the sella turcica prior to transsphenoidal surgery are reviewed in 141 patients who had biochemical evidence of pituitary-dependent Cushing disease. Axial thin-collimation CT scans with sagittal and coronal reformations before and after contrast enhancement were obtained in 125 patients. Seventy-eight patients had MR examinations with a 1.5-T superconducting magnet. In 11 of the patients gadolinium-enhanced MR scans were also obtained. The preoperative interpretation of the imaging studies was correlated with the surgical findings and patients follow-up. RESULTS: The sella turcica was enlarged in 43 cases (30%). In 125 patients reformatted or direct coronal thin-collimation CT scans were available. Seventy-eight of the patients had MR. In the 12 patients with pituitary macroadenomas, the accuracy of CT (n = 10) and MR (n = 10) in respect to detection of the lesion was 100%. Of the 98 microadenomas assessed by CT, 47 (48%) were directly depicted as distinct hypodense lesions. In only 31 of 73 cases (42%), however, could CT predict the precise anatomic location and extent of the lesions. Only patients in whom the hypercortisolism was corrected by later surgery were considered for the correlation analysis. Of the 52 microadenomas assessed by MR, 28 (53%) were directly depicted as distinct lesions of reduced signal intensity on T1-weighted images, and in only 21 of 41 cases (52%) did MR show good correlation to the surgical findings. Some degree of partially empty sella was found in 22% of the patients. CONCLUSIONS: Although both the sensitivity and the diagnostic accuracy of imaging methods of the sella turcica have been considerably improved in comparison with previous reports, they still provide only a minor contribution to the diagnosis and differential diagnosis of Cushing syndrome.     

Comparison of p53 and CD44 variant 6 expression between paired primary and recurrent ovarian cancer: an immunohistochemical analysis

PURPOSE: To assess the effect of the injection rate of contrast medium on pancreatic and hepatic enhancement at abdominal helical computed tomography (CT). MATERIALS AND METHODS: Sixty-four contrast medium-enhanced abdominal helical CT scans (64 adult patients) were obtained with 150 mL of contrast medium. The injection rate was 2.5 mL/sec for the first 32 scans and 5.0 mL/sec for the remaining 32. Scans were obtained at 5-sec intervals, with an intermediate 8-sec breathing interval. Hepatic and pancreatic enhancement levels were measured and averaged, and time-attenuation curves were plotted for both groups. Differences in weight, age, time to peak pancreatic and hepatic enhancement, and peak enhancement were assessed with the Student t test. RESULTS: Both peak enhancement and time to peak enhancement were significantly different between the two injection rates (P < or = .002), with faster, more intense hepatic and pancreatic enhancement at the higher rate. At 2.5 mL/sec, the pancreas reached a peak attenuation level of 65 HU at 69 sec, and the liver reached a peak of 58 HU at 87 sec. At 5.0 mL/sec, the pancreas reached a peak attenuation of 84 HU at 43 sec, and the liver reached a peak of 75 HU at 63 sec.     

Adrenal nonhyperfunctioning adenoma and nonadenoma: CT attenuation value as discriminative index

BACKGROUND: When an asymptomatic adrenal mass is incidentally discovered on abdominal CT scans, the distinction between a nonhyperfunctioning adenoma and a nonadenoma would be important. METHODS: We evaluated the CT findings of 36 adrenal masses (14 nonhyperfunctioning adenomas, 22 nonadenomas) in 34 patients with no evidence of hormonal hypersecretion. CT attenuation values of adrenal masses on CT scans were calculated by setting a circular region of interest as large as possible in the center of each adrenal mass. RESULTS: Below 20 HU in CT attenuation values, all adrenal masses, except one case of ganglioneuroma with myxomatous change, were nonhyperfunctioning adenomas. With an arbitrary threshold of 20 HU, the sensitivity of CT attenuation values in distinguishing nonhyperfunctioning adenomas from nonadenomas was 64%, the specificity was 95%, and the accuracy was 83%. When decreasing the threshold to 15 HU, the sensitivity was 64%, the specificity was 100%, and the accuracy was 86%. The CT attenuation value on noncontrast CT was more useful for making this distinction than the size and interior homogeneity. CONCLUSIONS: Our data suggest that an asymptomatic adrenal mass with homogeneous low attenuation (< or = 15 HU) and less than or equal to 4 cm indicates a nonhyperfunctioning adenoma, and no further examinations are necessary. CT attenuation value on non-contrast CT is the most important discriminatory factor.     

Determination of DNA content in salivary gland tumors

BACKGROUND: DNA content determination is a useful tool in the characterization of different malignant tumors. AIM: To measure DNA content in cells of salivary gland tumors as adjunct to histological diagnosis, correlating morphologic and biological features of these tumors. MATERIAL AND METHODS: From the archives of the Pathology service of a general hospital, 21 salivary gland tumors, 15 pleomorphic adenomas, 3 mucoepidermoid carcinomas and 3 cystic adenoid carcinomas were selected. DNA content was determined in the histological samples using a flow cytometric DNA analysis. RESULTS: All pleomorphic adenomas had a normal or diploid DNA content. Fifty percent of malignant tumors had an aneuploid DNA content (1 mucoepidermoid carcinoma and 2 cystic adenoid carcinomas). CONCLUSIONS: DNA determination may help in the histological diagnosis of salivary gland tumors. The presence of aneuploidy suggests malignity.     

Giant pleomorphic adenoma of the parotid gland: case report and review of the literature

Pleomorphic adenomas account for the majority of parotid masses, typically arising in the tail of the gland and enlarging slowly over time. The vast majority are 2 to 6 cm in size when resected. We report resection of the largest benign mixed tumor recorded in the modern English language literature. An 85-year-old reclusive woman had a 20-year history of an enlarging right periauricular mass that had begun bleeding several days prior to admission. The patient ultimately underwent resection of the mass, which measured 26 cm in diameter, weighed 6.85 kg, and proved on pathologic examination to be a benign mixed tumor without malignant degeneration. The implications of this unusual case for the management of mixed tumors are discussed, and a review of the world literature on giant pleomorphic adenomas is presented.     

Genetic characterization of an oral treponeme isolated from human subgingival plaque

INTRODUCTION: Since many benign and malignant pathologic conditions can appear as solitary pulmonary nodules, to establish nodule nature is always necessary for correct patient management. Recently, some authors have demonstrated the effectiveness of incremental dynamic CT in distinguishing cancerous from noncancerous lesions. The purpose of this work is to report our personal experience in this field. MATERIAL AND METHODS: We reviewed the incremental dynamic CT scans of 21 patients with a solitary pulmonary nodule < 3.5 cm phi without any calcifications, cavities and fat--namely, 15 carcinomas, 3 granulomas, 2 hamartomas, 1 abscess. Lesion density was evaluated before and 30 s, 1, 2, 3 and 5 min after contrast agent administration; we used a circular region of interest consisting of the central portion of the nodule in all cases and of 60-70% of its area in most cases. We subdivided the nodules into two groups, according to their enhancement: the nodules with > 20 HU and those with < 20 HU. All the lesions were submitted to surgery and histologic studies. RESULTS: Fourteen of 15 carcinomas and one hamartoma had contrast enhancement > 20 HU; an abscess exhibited marked ring-shaped contrast enhancement (positive predictive value: 87%). One carcinoma, three granulomas and one hamartoma had no contrast enhancement, or else it was < 20 HU (negative predictive value: 80%). DISCUSSION: Recently, some authors have demonstrated that malignant nodules, studied with incremental dynamic CT, have higher contrast enhancement than benign nodules. A value > 20 HU is a good predictor of malignancy (positive predictive value: 90%) and, conversely, a value < 20 HU is an unquestionable sign of benignity (negative predictive value: 100%). Our findings confirm the positive predictive value of enhancement > 20 HU, but not its negative predictive value because we found a malignant nodule without contrast enhancement. CONCLUSIONS: Incremental dynamic CT is an effective indicator of solitary pulmonary nodule nature, but its predictive value is not absolute and therefore this technique should be integrated with biopsy in the cases which are clinically or radiologically suspicious.     

Benign neoplasms in the parotid gland in the county of Copenhagen 1986-1995

In a ten year period from 1986-95 433 patients were submitted to operation due to benign tumours in the parotid gland in Copenhagen County. In this study we made a retrospective analysis of the surgical outcome. The incidence was calculated to be 6.8 benign tumours in the parotid gland per 100,000 persons per year. The histological distribution showed a frequency of 54% pleomorphic adenomas, 28% adenolymphomas and 18% other tumours. In the observation period there was a 3% recurrence rate in our material, most frequently the pleomorphic adenoma. The risk of permanent damage to the facial nerve was 1% for severe injury and 3% for affection of the ramus marginalis. Frey's syndrome was present in 50% of the patients, moreover the syndrome was observed many years after surgery. The frequency rate reached its highest level about five years postoperatively.     

Tumors arising in the palpebral lobe of the lacrimal gland

PURPOSE: Tumors arising in the palpebral lobe of the lacrimal gland are uncommon. There have been only eight reported patients, all of whom had pleomorphic adenomas. The authors present another six patients with primary palpebral lobe tumors. METHODS: The clinical presentation, computed tomographic, and pathologic findings of these six patients were reviewed. RESULTS: Tumor types include three pleomorphic adenomas, one well-differentiated adenoid cystic carcinoma, one carcinoma in pleomorphic adenoma, and one carcinoma ex pleomorphic adenoma. All six patients presented with a painless mass in the upper outer eyelid without significant displacement of the globe, but the superficial location of these lesions led to early detection. The tumors were localized to the lacrimal gland, predominantly anterior to the orbital rim. In all six patients, the involved palpebral lobe was removed, five via a direct anterior subcutaneous approach and one by superolateral orbitotomy. In two patients (adenoid cystic carcinoma and carcinoma ex pleomorphic adenoma), repeat surgery via superolateral orbitotomy was necessary to achieve complete removal of the lacrimal gland and surrounding tissue. No recurrences were detected during follow-up (range, 6 months to 7 years; mean, 26 months). CONCLUSION: Palpebral lobe tumors of the lacrimal gland are more common and consist of a greater variety of histologic types than previously described. In our series, these tumors comprise 17% of all epithelial lacrimal gland lesions. These are the first reported cases of malignancy in this location. A longer follow-up period is necessary to determine the true recurrence rate of these tumors.     

Antimicrobial susceptibility of periodontopathic bacteria associated with failing implants

Histological, immunohistochemical, and flow cytometric characteristics of three unusual parotid gland tumors are described. The patients were adult white men with carcinoma ex pleomorphic adenoma, true malignant mixed tumor, and primary parotid gland chondrosarcoma. The carcinoma ex pleomorphic adenoma showed evidence of simultaneous epithelial, myoepithelial, and mesenchymal differentiation by immunohistochemistry. The true malignant mixed tumor exhibited variable positivity for two keratins, vimentin, proliferating cell nuclear antigen, Ki67, and p53. The chondrosarcoma initially stained for vimentin, S100, muscle-specific actin, proliferating cell nuclear antigen, and Ki67, but it lost actin expression in its first recurrence, accompanied by more extensive Ki67 staining. DNA ploidy varied from diploid to aneuploid with intratumoral variation in the carcinosarcoma. S-phase fractions ranged from 2.43% to 13.9%. The findings underscore the diversity of tumors that may be pathogenetically related to, and at times derived from, pleomorphic adenoma.     

Multiplanar imaging in the preoperative assessment of metallic intraocular foreign bodies. Helical computed tomography versus conventional computed tomography

OBJECTIVE: This study aimed to compare the effectiveness of helical computed tomography (CT) versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies on axial, coronal, and multiplanar reconstruction images in clinical routine. DESIGN: Prospective comparative trial, alternate assignment of consecutive patients. PARTICIPANTS: Eighteen patients with penetrating eye injuries and suspected metallic intraocular foreign bodies were studied. INTERVENTION: Alternate patients were assigned to undergo either helical CT or conventional CT in the axial plane. Both the helical and the conventional data were transferred to a workstation, and reconstructions in the coronal and sagittal planes were performed. Additional direct coronal scanning was performed only when necessary for preoperative assessment. MAIN OUTCOME MEASURES: The quality of the directly obtained axial and coronal, as well as the reconstructed coronal and sagittal images, was assessed for each, imaging method based on the ability to detect and accurately localize foreign bodies. The size of the foreign bodies was measured and compared to the actual diameter. Total examination time and radiation dose delivered to the lens were measured for each imaging method. RESULTS: All foreign bodies were detected by each scanning method on the axial, the coronal, and on the reconstructed planes. The quality of the axial images was similar for helical and conventional CT. The helical technique provided high-quality reconstructed images comparable in quality to the directly obtained coronal planes in conventional CT. Reconstructions by conventional technique were not useful for preoperative assessment. The examination time for the total orbital volume was 18 seconds for helical CT examinations and 52 seconds for conventional CT examinations. Radiation dose delivered to the lens for the complete examination was 35 mGy for helical CT axial scanning, 56 mGy for conventional CT axial scanning, and 63 mGy for conventional CT coronal scanning. CONCLUSIONS: Helical CT multiplanar imaging offers several significant advantages for the preoperative assessment of metallic intraocular foreign bodies compared to the conventional CT technique in clinical practice, including short examination time, reduced motion artifacts, reduced radiation exposure, and the ability to obtain diagnostically useful coronal and sagittal reconstruction images without the need for additional scanning.     

Treatment outcome of 1,000 cases of endoscopic sinus surgery

To assess the treatment outcome of endoscopic sinus surgery (ESS), 1,000 patients with chronic sinusitis and nasal polyp treated between November 1991 and January 1995 were included in this study. Among them, 754 patients (64.8%) had previous operations from 1 to 25 times with an average of 3.7. Before ESS, axial and coronal CT scans were obtained (window width: 1,000 HU, window level: +90 HU; section thickness: 2 mm with 12 to 16 sections). Patients with clinical stages from I to IV were 9.9%, 21.0%, 15.0% and 54.1% respectively. Bilateral ESS was performed in 95% patients, septoplasty in 27.6%, middle meatal antrostomy in 78.5%. The clinical cure rate was 84.0%, 557 patients were considered as primary healing, 283 patients delayed healing and 160 patients had persistent inflammation. Complications were noted in 18 patients. Bleeding during ESS varied from 10 to 1,800 ml (average 180 ml). The indications, preoperative evaluation, control of bleeding, prevention of complications and prognosis were discussed in detail. The article indicated that the important factors to increase the cure rate are postoperative follow-up and systematic treatment.     

Tyrosine-rich crystals associated with oncocytic salivary gland neoplasms

OBJECTIVE: Crystalloids have been identified ultrastructurally within the epithelial cells of Warthin's tumors, but there have been no studies characterizing crystals or crystalloids in Warthin's tumors by light microscopy. The finding of abundant needle-shaped crystals in a fine-needle aspirate of a cystadenoma of the parotid prompted us to examine the prevalence of crystals and crystalloids in oncocytic salivary gland neoplasms. DESIGN: Ninety-seven oncocytic neoplasms (93 Warthin's tumors, 3 cystadenomas, and 1 oncocytoma) excised at our institution between 1950 and 1996 were examined, to identify crystals. Neoplasms with crystals were further characterized by means of a variety of histochemical stains and electron microscopy. Ninety-nine pleomorphic adenomas were similarly reviewed. RESULTS: Seven cases with crystals were identified. Five of these were Warthin's tumors, 1 was a cystadenoma, and 1 was an oncocytoma. The crystals were noted within tumor cysts but were not limited to the neoplasms. The crystals were predominantly either needle-shaped or tabular, but some cases contained mixtures of both as well as intermediate forms. They stained pink with hematoxylin-eosin, although the tabular forms also exhibited a focal yellow hue. The crystals were not discernible under polarized light. They stained a red-brown color with Millon's reagent, which indicated the presence of tyrosine. Trichrome, periodic acid-Schiff stain with diastase, alcian blue (pH 2.5), and Congo red stains were negative. Electron microscopy revealed sharply defined, elongate, electron-dense structures with periodicity, both extracellular and within epithelial cells. No crystals or crystalloids were identified in any of 99 pleomorphic adenomas reviewed. CONCLUSIONS: The findings indicate that tyrosine-rich crystals associated with several oncocytic salivary gland neoplasms are morphologically, histochemically, and ultrastructurally distinct from previously described tyrosine-rich crystalloids and collagenous crystalloids of pleomorphic adenomas. Although the crystals appear to form by the assembly of small units within epithelial cells, the exact mode of formation remains unclear.     

Weight, length, ponderal index, and intrauterine growth retardation in Brazil

INTRODUCTION: In 1967, Kleinsasser first reported about basal cell adenomas in salivary glands, which represent approximately 1-2% of all salivary gland tumors. About 70% of these tumors are found in the parotid gland. Less often the minor salivary glands are involved, particularly in the upper lip region. We would like to report on a case of occurrence in the upper pole of the palatine tonsil. CASE REPORT: A 68-year-old woman was seen, who complained about a growth in her left tonsil. Other than a slow increase size, she had no symptoms. Examination revealed a solid tumor approximately 3 cm in diameter which displaced the upper part of the tonsil medially. In an MRI study, the neoplasia demonstrated a low signal intensity in the T1-weighted images and a high signal intensity in the T2-weighted images, which is relatively typical for a cystic structure. The tumor extended to the base of skull, and was completely resected by extended tonsillectomy. Histologic studies showed a cystic, regressive basal cell adenoma. DISCUSSION: When compared to pleomorphic adenomas, basal cell adenomas are relatively rare in the region of the soft palate. This case is especially interesting because we assume the origin of the tumor to be in the supratonsillar salivary glands (Weber's glands) and also because of the unusually pronounced cystic regressive changes.     

The effect of helical pitch and beam collimation on the lesion contrast and slice profile in helical CT imaging

A model is presented in this paper to describe how the contrast of a reconstructed object and slice sensitivity profile are affected by (1) the table speed or helical pitch, (2) the x-ray collimations, (3) the size of the object, (4) the alignment between the reconstructed slice and the object, (5) the distance of the object from the axis of rotation, and (6) the helical CT reconstruction algorithm employed. This contrast model is validated by both computer simulations and experiments. With this model, the contrast of a reconstructed object, slice sensitivity profile, and the longitudinal MTF can be accurately predicted. The optimal scan strategy and the point of diminishing returns can be determined prior to scanning. Several conclusions can be drawn from this model. First, overlapping reconstruction significantly improves overall scan contrast sensitivity of helical CT. Second, with a given x-ray collimation, low pitch helical scans provide better longitudinal resolutions. Third, with a given volume coverage rate (i.e., a given table speed), narrow collimation high pitch helical scans provide better longitudinal resolutions than wide collimation low pitch ones and therefore are recommended for high-contrast thin-slice applications. A lesion conspicuity model is also established.     

Pediatric tuberculosis in rural South Africa--value of directly observed therapy

The case is reported of a 27-year-old patient who developed multiple recurrences of a carcinoma arising from richly stromal pleomorphic adenoma of the parotid gland over 13 years. Originally the tumor was classified as a benign pleomorphic adenoma because there were no cytological characteristics of malignancy. Later on the diagnosis had to be modified to that of a carcinoma arising from a pleomorphic adenoma because of the infiltrating growth pattern of the tumor. A multicentric local recurrence and metastases on the left side of the neck supported the correct diagnosis. This case demonstrates that, beside the classic cytological criteria of malignancy invasion and penetration of the capsule can be decisive for the diagnosis of malign transformed pleomorphic adenoma. Treatment and prognosis of salivary gland tumors assume a clear determination of their diguity. The unusual course in this case of a pleomorphic adenoma originally diagnosed as benign demonstrates the importance of regular follow-up.