Performance and environmental impact of egg production in response to dietary supplementation of mannan oligosaccharide in laying hens: a meta-analysis

A meta-analysis was conducted to examine the effect of supplementing mannan oligosaccharide (MOS; Bio-Mos, Alltech Inc., Nicholasville, KY) in the diets of laying hens on the performance and environmental impact of egg production. Data on production performance (feed intake, hen-day production [HDP], feed conversion ratio [FCR], and mortality) and egg quality attributes (egg weight, egg mass, and eggshell thickness) were extracted from 18 studies to build a database of comparisons between nonsupplemented diets (control) and diets supplemented with MOS. A total of 4,664 laying hens were involved in the comparisons and the average MOS dosage and age of hens were 0.97 kg/ton and 44 wk, respectively. The dataset was analyzed using the random-effects model to estimate the effect size of MOS supplementation on production performance and egg quality attributes. The impact of feeding MOS on the carbon footprint (feed and total emission intensities) of egg production was evaluated by using the meta-analysis results of production performance to develop a scenario simulation that was analyzed by a life cycle assessment (LCA) model. Overall pooled effect size (raw mean difference) indicated that MOS supplementation did not affect feed intake. In contrast, HDP increased by +1.76% and, FCR and mortality reduced by -26.64 g feed/kg egg and -2.39%, respectively. Dietary MOS did not influence egg weight while egg mass increased (P < 0.01) by +0.95 g/day/hen and eggshell thickness tended to increase (P = 0.07) by +0.05 mm. Subgroup analysis indicated that dietary MOS exhibited consistent improvement on HDP and FCR under several study factors (age of hens, number of hens, production challenges, MOS dosage, and study duration). Additionally, the simulated LCA revealed that supplementing MOS decreased feed and total emission intensities of egg production by -1.3 and -1.5%, respectively. Overall, dietary supplementation of MOS at 1.0 kg/ton improved the production performance of laying hens and reduced the carbon footprint and, therefore, can enhance the sustainability credentials of egg production.

Toxicological evaluation of a glycan preparation from an enzymatic hydrolysis of Saccharomyces cerevisiae

The aim of this paper was to provide a comprehensive toxicological and safety evaluation of a yeast cell wall preparation (YCWP) for use as an animal feed ingredient. The following toxicological assessments were carried out: the mutagenic activity was tested using the Ames' Test in five Salmonella typhimurium strains; clastogenic activity was investigated using the mammalian micronucleus test in Swiss ICO OF1 (IOPS Caw) mice; genotoxic activity was assessed using the in vitro mammalian chromosomal aberration test in human lymphocytes; acute oral toxicity was tested by administration of a single dose of 2000 mg/kg BW. Eye and skin irritation were assessed in rabbits according to OECD guidelines; skin sensitivity was established in guinea pigs by means of the Buehler test, while acute dermal and inhalation studies in rats were further completed, also according to OECD guidelines. All conducted tests were considered valid under the experimental conditions. No significant mutagenic activity or genotoxic activity was observed, and it was concluded that the test article did not induce any clastogenic effect. YCWP was found to be mildly irritating to the eye, slightly irritating to the skin but was found to be non-sensitizing in the guinea pig. The acute oral, dermal and inhalation studies did not yield any evidence of gross toxicity or pharmacological effects.

Toxicological evaluation of an unextracted Aurantiochytrium limacinum biomass, a novel docosahexaenoic acid rich feed ingredient

The purpose of this paper was to evaluate the toxicological potential of a heterotrophically grown unextracted Aurantiochytrium limacinum biomass (AURA) when used as a food additive. The following toxicological assessments were conducted on this novel docosahexaenoic acid rich feed ingredient: Mutagenic activity was tested by means of the Ames' test using five Salmonella typhimurium strains; clastogenic activity was investigated using the micronucleus test in male and female Sprague Dawley rats; genotoxic activity was assessed by means of the in vitro metaphase analysis tests in human lymphocytes; oral toxicity was tested by administration of AURA at various concentrations; eye and skin irritation was assessed in rabbits according to OECD guidelines; skin sensitivity was established in guinea pigs by means of the Buehler test. All conducted tests were considered valid under the experimental conditions. No significant mutagenic activity or clastogenic activity was observed. Genotoxic activity in human lymphocytes was not induced. Oral administration of 276 mg AURA/kg bw¹ and 2000 mg AURA/kg bw resulted in no mortality or signs of acute toxicity. Daily administration of 1000 mg AURA/kg bw caused no mortality or biologically relevant signs of toxicity and was established as the No Observable Adverse Effect Level. AURA was also found to be a non-irritant for the eye and skin of the rabbit and was non-sensitizing to guinea pig skin.

Heterotrophic Aurantiochytrium sp. supplementation to layer diets sustainably increases the omega-3 concentration of eggs

1. The consumption of adequate amounts of the long-chain polyunsaturated omega-3 fatty acids (n-3 LC-PUFA) has been associated with beneficial effects on human health. Eggs are commonly consumed worldwide, and their omega-3 content can be easily altered by changing the diets of laying hens and so represent an important target for enrichment. 2. In this study, the effect of supplementing laying hens with DHA-rich, Aurantiochytrium limacinum at three different inclusion levels was investigated over a 24-week period. 3. Significant increases in egg DHA concentrations were observed after four weeks and were maintained for the duration of the 24-week study. The supplemented eggs in the current study had a DHA content of 82, 101, and 129 mg/yolk when supplemented with 0.25%, 0.5% and 1% treatments, respectively, which meets the EU criteria to be considered 'high in omega-3'. 4. Using the sustainably grown protist Aurantiochytrium limacinum to supplement layer diets increased the egg DHA concentration and decreased the n-6/n-3 ratio, improving the nutritional value of the eggs for human consumers.

Redressing the balance: including DHA-rich Aurantiochytrium limacinum in broiler diets increases tissue omega-3 fatty acid content and lowers the n-6:n-3 ratio

1. The consumption of sufficient quantities of long chain omega-3 fatty acids (n-3 LCPUFA) from meat and other animal products can lead to a variety of health benefits in humans. The fatty acid content of poultry meat can be increased by feeding birds ingredients that are rich in n-3 LCFUFA 2. The effect of feeding a docosahexaenoic acid (DHA) rich Aurantiochytrium limacinum biomass (AURA) on the fatty acid content of breast and thigh tissues was investigated in a feeding trial with 2880 male Ross 308 broilers. The broiler diets were supplemented with either 0, 0.25, 0.5 or 1% AURA from day 21 to 42 of age. 3. Supplementation significantly increased the DHA content of both breast and thigh meat at an inclusion rate of 1% in the diet, leading to a total of 42 and 46 mg DHA/100 g of fresh breast or thigh tissue respectively. Significant increases in the tissue eicosapentaenoic acid (EPA) concentration were seen alongside a reduced omega-6/omega-3 ratio, improving the nutritional value of the meat for consumers and identifying supplementation of broiler diets with A. limacinum as an effective and sustainable method to increase n-3 LCPUFA consumption in the human population.

The effect of dietary supplementation with Aurantiochytrium limacinum on lactating dairy cows in terms of animal health, productivity and milk composition

The aim of this study was to investigate the effect of dietary supplementation with the docosahexaenoic acid (DHA)-rich microalgae, Aurantiochytrium limacinum (AURA), on a variety of health and productivity parameters in lactating cows. Twenty-four cows were blocked by parity and number of days in milk and then randomly assigned to a control (CON; n = 12) group with no algal supplementation, or a treatment group (AURA; n = 12) provided with 100 g AURA cow^-1  day^-1 or 16 g DHA cow^-1  day^-1 . A variety of health and productivity measurements were taken, and results indicated that supplementation had no negative effects on animal health in terms of somatic cell count, haematological and biochemical blood parameters, while body condition was marginally improved by algal supplementation. No differences were found for the various production parameters measured; however, a tendency towards increased milk production was observed for the AURA group during the final stage of the study (+4.5 kg cow^-1  day^-1 , day 78-84). The fatty acid profile of milk was improved by supplementation, with significantly lower saturated fatty acids, significantly higher omega-3 fatty acids and an improved omega-3/omega-6 ratio observed when compared to the control group. The amount of DHA in the milk of cows provided 105 g AURA head^-1  day^-1 was 4.7 mg/100 g milk with a peak transfer efficiency from feed to milk at day 49 of 8.3%. These results indicate that supplementation with 105 g AURA head^-1  day^-1 resulted in the successful enrichment of milk with DHA without negatively impacting the health or productivity of the animals.

Dietary safety of a dual-enzyme preparation for animal feed: Acute and subchronic oral toxicity and genotoxicity studies

Animal feed is routinely supplemented with exogenous enzymes to improve nutrient utilization, such as proteases to enhance protein hydrolysis in vivo and xylanases to alleviate feed related anti-nutritional factors. The present studies were conducted to evaluate the potential oral toxicity and genotoxicity of a dual-enzyme preparation, Vegpro^® concentrate (VPr-C). Acute oral toxicity studies were conducted in adult male and female Sprague-Dawley Crl CD rats and CHS Swiss ICO:OFI (IOPS Caw) mice. Thirteen week preliminary and final subchronic oral toxicity studies were conducted in male and female rats. Genotoxicity was evaluated through a bacterial reverse mutation test (Ames test), an in-vitro mammalian chromosomal aberration test, and a mammalian micronucleus test. The LD₅₀ was >2000 mg/kg of BW in mice and rats. In the 13-week oral toxicity study, the No Observed Adverse Effects Level (NOAEL) was 1000 mg/kg BW per day for females and 300 mg/kg BW per day for males. VPr-C showed no mutagenic activity in Salmonella typhimurium, did not induce significant chromosomal aberrations in cultured human lymphocytes, and did not increase the frequency or proportion of micronucleated immature erythrocytes in mice. There was no evidence of acute or subchronic toxicity or genotoxicity associated with the test article at these test dosages.

Comparison of the sequestering properties of yeast cell wall extract and hydrated sodium calcium aluminosilicate in three in vitro models accounting for the animal physiological bioavailability of zearalenone

The sequestration/inactivation of the oestrogenic mycotoxin zearalenone (ZEA) by two adsorbents--yeast cell wall extract (YCW) and hydrated sodium calcium aluminosilicate (HSCAS)--was studied in three laboratory models: (1) an in vitro model was adapted from referenced methods to test for the sequestrant sorption capabilities under buffer conditions at two pH values using liquid chromatography coupled to a fluorescence detector for toxin quantification; (2) a second in vitro model was used to evaluate the sequestrant sorption stability according to pH variations and using ³H-labelled ZEA at low toxin concentration; and (3) an original, ex vivo Ussing chamber model was developed to further understand the transfer of ZEA through intestinal tissue and the impact of each sequestrant on the mycotoxin bioavailability of ³H-labelled ZEA. YCW was a more efficient ZEA adsorbent than HSCAS in all three models, except under very acidic conditions (pH 2.5 or 3.0). The Ussing chamber model offered a novel, ex vivo, alternative method for understanding the effect of sequestrant on the bioavailability of ZEA. The results showed that compared with HSCAS, YCW was more efficient in sequestering ZEA and that it reduced the accumulation of ZEA in the intestinal tissue by 40% (p < 0.001).

Effects of mannan oligosaccharide on cytokine secretions by porcine alveolar macrophages and serum cytokine concentrations in nursery pigs

This study explored the hypothesis that mannan oligosaccharide (MOS) acts to reduce systemic inflammation in pigs by evaluating cytokine production of alveolar macrophages (AM) and serum cytokine concentrations. A total of 160 pigs were fed diets containing 0.2 or 0.4% MOS for 2 or 4 wk postweaning compared with control diets without MOS. Dietary MOS did not affect the serum concentration of tumor necrosis factor (TNF)-α and tended (P = 0.081) to increase that of IL-10. These cytokine concentrations also changed over time (P < 0.001). After 2-wk feeding of the control or MOS diets, AM were collected and stimulated ex vivo with lipopolysaccharide (LPS) or polyinosinic:polycytidylic acid (PLIC) as infection models. The LPS-stimulated AM from MOS-fed pigs (n = 12) secreted less TNF-α (P < 0.001) and more IL-10 (P = 0.026) than those from control-fed pigs (n = 6). However, dietary MOS had less effect on ex vivo TNF-α and IL-10 production by PLIC-stimulated AM (P = 0.091 and P > 0.10, respectively. Further, effects of MOS were examined in 4 in vitro experiments. In Exp. 1 (n = 4 pigs), MOS and mannan-rich fraction (MRF), when added to AM cultures, were able to increase TNF-α production. This direct effect of MOS was not due to endotoxin contamination as verified in Exp. 2 (n = 6 pigs) using polymyxin B, an inhibitor of LPS activation of toll-like receptor 4. Polymyxin B inhibited production of TNF-α by AM after treatment with LPS (P < 0.001), but not after treatment with MOS in the absence of LPS (P > 0.70). In Exp. 3 (n = 6 pigs), when MOS was directly applied in vitro, the pattern of cytokine production by LPS-activated AM was similar to that observed ex vivo, as MOS suppressed LPS-induced TNF-α (P < 0.001) and enhanced LPS-induced IL-10 (P = 0.028). In Exp. 4 (n = 6 pigs), when MRF replaced MOS, AM-produced TNF-α induced by LPS or PLIC was suppressed by MRF (P = 0.015 or P < 0.001, respectively). These data establish that MOS and MRF suppress LPS-induced TNF-α secretions by AM. Generally, the study suggests that MOS may be a potent immunomodulator because it directly activates AM to secrete TNF-α and alters the cytokine responses of bacterial endotoxin-induced AM in both ex vivo and in vitro systems. In particular, feeding MOS to pigs for 2 wk reduces TNF-α and increases IL-10 concentrations after ex vivo treatment of AM with LPS. These immunomodulatory properties of MOS may have important implications for both host defense and avoidance of harmful overstimulation of the immune system.

Mannan oligosaccharide modulates gene expression profile in pigs experimentally infected with porcine reproductive and respiratory syndrome virus

This study characterized gene expression in peripheral blood mononuclear cells (PBMC) and bronchoalveolar lavage fluid (BALF) cells from control- or mannan oligosaccharide (MOS)-fed pigs with or without porcine reproductive and respiratory syndrome virus (PRRSV) at d 7 postinfection (PI). Weaned pigs (3 wk old) fed 0 or 0.2% MOS (Bio-Mos) diets were intranasally inoculated with PRRSV or a sterile medium at 5 wk of age. Total RNA (3 pigs/treatment) was extracted from cells. Double-stranded cDNA was amplified, labeled, and further hybridized to the Affymetrix GeneChip Porcine Genome Array consisting of 23,937 probe sets representing 20,201 genes. Microarray data were analyzed in R using packages from the Bioconductor project. Differential gene expression was tested by fitting a mixed linear model equivalent to a 2 × 2 factorial ANOVA using the limma package. Dietary MOS and PRRSV changed the expression of thousands of probe sets in PBMC and BALF cells (P < 0.05). The MOS × PRRSV interaction altered the expression of more nonimmune probe sets in PBMC (977 up, 1,128 down) than in BALF cells (117 up, 78 down). The MOS × PRRSV interaction (P < 0.05) for immune probe sets in PBMC affected genes encoding key inflammatory mediators. In uninfected pigs, gene expression of IL-1α, IL-6, myeloid differentiation factor 88, Toll-like receptor (TLR) 4, major histocompatibility complex (MHC) II, and dead box polypeptide 58 increased in PBMC of MOS-fed pigs (P < 0.05). This suggests that MOS enhances disease resistance in pigs and supports the fact that MOS induced a rapid increase in leukocytes at d 3 and 7 PI. Within infected pigs, however, MOS reduced the expression of IL-1β, IL-6, IL-8, macrophage inflammatory protein (MIP)-1α, MIP-1β, monocyte chemotactic protein (MCP)-1, and TLR4 genes in PBMC (P < 0.05). This finding may explain why fever was ameliorated in infected pigs fed MOS by d 7 PI. The expression of IL-1β, IL-6, MIP-1β, MCP-1, and TLR4 genes was confirmed by quantitative real-time reverse-transcription PCR. In BALF cells of infected pigs, MOS reduced the gene expression of TLR4, MHCII, and molecules associated with the complement system, but increased the gene expression of MHCI. In short, MOS regulated the expression of nonimmune and immune genes in pig leukocytes, perhaps providing benefits by enhancing the immune responses of the pigs to an infection, while preventing overstimulation of the immune system.

Mannan oligosaccharide improves immune responses and growth efficiency of nursery pigs experimentally infected with porcine reproductive and respiratory syndrome virus

This study was conducted to determine whether the ingestion of mannan oligosaccharide (MOS, Bio-Mos) alters the immune response of nursery pigs challenged with porcine reproductive and respiratory syndrome virus (PRRSV). A total of 64 pigs (3 wk old), free of PRRSV, were used in 2 separate but similar experiments conducted sequentially. Pigs were blocked by initial BW. Sex and ancestry were equalized across treatments. Pigs were randomly assigned from within blocks to 1 of 4 treatments in a 2 × 2 factorial arrangement [2 types of diet: control (0%) and MOS addition (0.2%); 2 levels of PRRSV: with and without]. There were 8 replicate chambers of 2 pigs each. After 2 wk of a 4-wk period of feeding the treatments, pigs were intranasally inoculated with PRRSV or a sterile medium at 5 wk of age. The PRRSV challenge decreased ADG, ADFI, and G:F throughout the experiment (P < 0.001). Feeding MOS improved G:F of the pigs during d 7 to 14 (P=0.041) postinfection (PI). Serum concentrations of tumor necrosis factor (TNF)-α, C-reactive protein, and haptoglobin were increased by PRRSV (P < 0.001). The MOS × PRRSV interaction was significant for TNF-α at d 14 PI (P=0.028), suggesting that infected pigs fed MOS had less TNF-α than those fed the control. Dietary MOS increased serum IL-10 at d 14 PI (P=0.036). Further, MOS-fed pigs had greater numbers of white blood cells (WBC) at d 3 (P=0.048) and 7 PI (P=0.042) and lymphocytes at d 7 PI (P=0.023) than control-fed pigs. In contrast, PRRSV decreased (P < 0.01) WBC numbers until d 14 PI. Dietary MOS appeared (P=0.060) to increase the neutrophils in PRRSV-infected pigs at d 3 PI, but no (P=0.202) MOS × PRRSV interaction was found. Infection with PRRSV increased rectal temperature (RT) of pigs at d 3 PI (P < 0.001) and continued to affect the infected pigs fed the control diet until d 14 PI. The MOS × PRRSV interaction for RT was found at d 7 (P < 0.01) and 10 (P=0.098) PI, indicating that the infected pigs fed MOS had a decreased RT compared with those fed the control. This could explain why feed efficiency was improved by MOS. No effect (P > 0.05) of treatments on viremia or PRRSV-specific antibody was observed. These results suggest that MOS is associated with rapidly increased numbers of WBC at the early stage of infection and alleviates PRRSV-induced effects on G:F and fever. The results also indicate that the reduced intensity of inflammation by MOS may be related to changes in inflammatory mediator levels at the end of the acute phase.

Influence of posture on the incidence of vein cannulation during epidural catheter placement

BACKGROUND AND OBJECTIVE

Epidural vein cannulation has long been recognized as a problem in parturients due to distension of epidural veins. Epidural vein engorgement is maximal when the pregnant woman is in the supine position and minimal in the lateral position. Following an initial observation of an apparently high incidence of epidural vein cannulation in the sitting position, a randomized trial was conducted to document whether such an association existed.

METHODS

A total of 209 term parturients were randomized to either the sitting or lateral position (107 left lateral, 102 sitting). Epidural catheter placement was achieved using a loss of resistance to air technique with an 18-G Tuohy needle. A data sheet was completed for each patient recording patient position, patient characteristics data, stage in labour and the incidence of epidural vein cannulation. Poor labour analgesia was defined as a visual analogue scale (VAS) > 40 mm on a 0-100 mm pain intensity VAS.

RESULTS

The risk of epidural vein cannulation was significantly higher in the sitting group (16 of 102 = 15.7%) compared with the lateral position group (4 of 107 = 3.7%), P = 0.011. There was a significant association between epidural vein cannulation and poor analgesia (P = 0.006). These two variables remained independently significant on multiple regression analysis (position, P = 0.009; analgesia, P = 0.006).

CONCLUSIONS

We conclude that there is a direct correlation between the incidence of epidural vein cannulation and patient posture during epidural catheter insertion in parturients.

Carcinomas arising in multilocular thymic cysts of the neck: a clinicopathological study of three cases

AIMS

To report three cases of primary carcinoma of the neck arising in multilocular thymic cysts (MTC).

METHODS AND RESULTS

The patients were three men aged 47, 50 and 52 years who presented with a painless neck mass of several weeks' duration. The patients had no history of previous surgical procedures or of malignancy elsewhere. The tumours in all three patients were located on the right lateral side of the neck; all patients underwent complete surgical resection of the mass. Grossly, the tumours were cystic and measured between 20 and 30 mm in greatest diameter. Histologically, the tumours showed cyst walls lined by squamous epithelium. The cyst walls contained prominent germinal centres with lymphoid hyperplasia, cholesterol cleft granulomas, and scattered keratinized structures reminiscent of Hassall's corpuscles. In addition, a neoplastic cellular proliferation composed of round to oval cells arranged in sheets and originating from the lining of the cystic structures was present. The neoplastic cells showed moderate amounts of eosinophilic cytoplasm, round nuclei, and, in some areas, prominent nucleoli. Mitotic figures were easily found, and cellular pleomorphism was present in several areas. In two cases the tumours showed features of basaloid carcinoma of the thymus, while in one case the pattern was that of squamous cell carcinoma. Immunohistochemical studies for keratin showed a strong positive reaction in the tumour cells, while leucocyte common antigen strongly stained the lymphoid background. Follow-up information obtained in two patients showed them to be alive 6 months after initial diagnosis. One patient was lost to follow-up.

CONCLUSION

The cases described here represent an unusual variant of carcinoma arising in multilocular thymic cyst in the neck region.

Cystic sclerosing haemangioma of the lung

AIMS

To present three cases of sclerosing haemangioma of the lung (SHL) with prominent cystic changes.

METHODS AND RESULTS

The patients were three women, 27, 35, and 64 years of age. In two cases, the lesion was found on routine chest X-ray and in both instances the diagnosis of SHL was not entertained in the radiological differential diagnosis. In one case, the finding was discovered on post mortem examination. Grossly, the lesions were well-circumscribed and cystic. Histologically, the tumours were characterized by a dual population of small and large bland-appearing neoplastic cells growing in a predominantly cystic pattern. Immunohistochemical staining for epithelial membrane antigen by tumour cells was consistently positive in all three cases. All tumours were negative for keratin, CD34, factor VIII, and S100. The two patients in whom the lesion was identified ante-mortem are alive and free of disease 4 and 7 years after surgical excision.

CONCLUSIONS

The present cases indicate that sclerosing haemangioma may present as a cystic pulmonary neoplasm; such a presentation should be taken into consideration when assessing cystic pulmonary lesions.

Primary signet ring cell adenocarcinomas of the lung: a clinicopathological study of 15 cases

AIMS

We describe the clinicopathological characteristics of 15 cases of primary signet ring cell adenocarcinoma of the lung and highlight the importance of recognizing that not all adenocarcinomas with signet ring cell features represent metastatic adenocarcinomas.

METHODS AND RESULTS

We evaluated the clinicopathological and immunohistochemical features of 15 cases of signet ring cell adenocarcinoma of the lung. The patients were 12 men and three women, age 30-75 years (mean 52.5 years). No evidence of a primary tumour elsewhere could be found on thorough clinical examination. Nine patients underwent resection and the remainder were biopsied. The tumours ranged from 18 to 80 mm in greatest dimension. Microscopically, two distinct patterns of growth were recognized: acinar and diffuse. The tumours were characterized by the presence of >75% signet ring cells. Periodic acid-Schiff and mucicarmine showed strong intracellular positive staining. Immunohistochemical stains for TTF-1 (6/6) and CEA (9/9) showed strong positive reaction in all cases evaluated. Three out of six cases were also positive for cytokeratin 7. All the tumours (6/6) were negative for cytokeratin 20, ER, PR and GCDFP-15. Follow-up information was obtained in 11 patients; six patients died within 1 year and five patients were alive from 3 to 36 months after initial diagnosis.

CONCLUSION

These cases highlight an unusual histological growth pattern of primary lung adenocarcinoma that may be mistaken for a metastasis from an occult primary. The recognition of this pattern of lung tumours is important for proper treatment.

Thymoma with prominent cystic and hemorrhagic changes and areas of necrosis and infarction: a clinicopathologic study of 25 cases

Twenty-five cases of thymoma with prominent cystic and hemorrhagic changes and areas of necrosis and infarction are presented. The patients were 11 women and 14 men between the ages of 18 and 73 years (median 45.5 years). Clinically, nine patients were asymptomatic and their mediastinal tumor was discovered on routine chest radiograph. Sixteen patients presented with symptoms of chest pain and cough. All patients underwent surgical resection of their tumor. Grossly, the tumors were described as well circumscribed and encapsulated, with the exception of two that showed infiltration of pleura and pericardium. The tumors measured from 4 to 13 cm in greatest dimension. On cut surface they showed prominent cystic areas and foci of hemorrhage and necrosis. Histologically, the tumors contained solid areas showing an admixture of round to oval epithelial cells devoid of atypia admixed with small lymphocytes in varying proportions. Cystic changes with areas of necrosis, infarction, and hemorrhage were present in all cases and comprised extensive areas of the tumors. The areas of infarction showed features of ischemic necrosis and were always intimately associated with vaso-occlusive and thrombotic phenomena and with cystic and hyperplastic changes of adjacent thymic epithelium. Clinical follow-up in 14 patients showed that 11 were alive and well from 1 to 18 years after surgery (median follow-up 9 years). Three patients died: one of complications during the immediate postoperative period, one because of colonic adenocarcinoma 9 years after diagnosis of the mediastinal tumor, and one because of pneumonia 6 years later. The two patients with invasive tumors were lost to follow-up. The present study appears to indicate that areas of hemorrhage and necrosis in well encapsulated, noninvasive thymomas do not portend an adverse prognosis.

Pleural amyloidosis mimicking mesothelioma: a clinicopathologic study of two cases

Two cases of pleural amyloidosis are presented. The patients are two men, 70 and 72 years of age respectively. Neither patient had evidence of systemic amyloidosis. Each presented clinically with symptoms of chest pain and dyspnea. Radiologically, both patients showed diffuse pleural thickening similar to that observed in malignant mesothelioma. In both patients, surgical decortication of the pleura was performed. Histologically, the lesions were characterized by the presence of an amorphous eosinophilic material with focal collections of a lymphoplasmacytic infiltrate. Focal clusters of giant cells were admixed with the lymphoplasmacytic infiltrate. Histochemical stains for Congo red showed strong positive apple-green birefringency. Immunohistochemical studies using kappa and lambda light chains showed polyclonality. The cases discussed herein represent an unusual presentation of amyloid and one that needs to be considered in the differential diagnosis of malignant mesothelioma.

Immunohistochemical differential diagnosis of pleural effusions, with emphasis on malignant mesothelioma

The immunohistochemical diagnosis of atypical epithelial proliferations in pleural fluid is a challenging topic in cytopathology and surgical pathology. Mesothelioma may be simulated clinically and radiologically by several other nonneoplastic and neoplastic disorders, mandating that strict histologic, histochemical, immunohistochemical, and ultrastructural guidelines be followed for its diagnosis. Because of its availability to most laboratories, immunohistochemistry has emerged as the most commonly used procedure for the diagnosis of pleural malignancies. This review considers the current status of that investigative modality, with particular attention to lesions that are suspected to be mesothelial.

Neuroendocrine neoplasms of the mediastinum

Neuroendocrine neoplasms of the mediastinum form part of a family of tumors characterized by genotypic, immunophenotypic, and functional properties of neuroendocrine differentiation. Although rare, these tumors have been the source of much attention and controversy in the literature. Their nomenclature and classification, in particular, have continued to evolve over the years. Such tumors comprise lesions derived from neuroendocrine elements within the thymus, from paraganglionic rests, or from misplaced embryonal structures within the mediastinum. The most common neuroendocrine neoplasms of this anatomic region, however, correspond to neuroendocrine carcinomas of the thymus. The light microscopic, immunohistochemical, and ultrastructural features of these tumors are reviewed along with the advances in our understanding of these lesions and current trends in nomenclature and terminology.

Cutaneous B-cell lymphoma with signet ring-cell morphology: a clinicopathologic and immunohistochemical study of three cases

Three cases of primary cutaneous B-cell lymphoma with prominent signet ring-cell features are presented. The patients were three men between the ages of 37 years and 74 years (average, 55.5 years). Clinically, the three patients presented with multiple skin nodules. In one patient, the nodules had been present for approximately 5 weeks, although in the two other patients, the nodules were of unknown duration. The lesions were located in the upper extremities (forearm) and measured from 2 cm to 3 cm in diameter. No evidence of lymphadenopathy was observed in any of the patients. Surgical excision of the nodules was performed. Histologically, in two cases, the superficial and deep dermis was replaced by a diffuse cellular proliferation, and in one patient, the tumor cell population adopted a nodular pattern of growth involving adnexal structures and infiltrating the subcutaneous fat. In all cases, the tumors were composed of cells showing signet ring-cell features, with striking indentation of the nuclei toward the periphery of the cell. Immunohistochemical studies using antibodies for B-cell and T-cell markers (L-26 and UCHL) as well as antibodies for leukocyte common antigen, keratin, and kappa and lambda light chains were performed in all cases. The tumor cells showed a positive reaction for leukocyte common antigen, L-26, and lambda light chain restriction. Follow-up information was only available in one patient, who has remained alive and well 2 years after diagnosis without evidence of progression of the disease. The present cases highlight the importance of recognizing this unusual morphologic type of lymphoma so as to arrive at a correct diagnosis.

"Juvenile" xanthogranuloma: an immunophenotypic study with a reappraisal of histogenesis

The non-Langerhans histiocytoses, a nosologic category to which juvenile xanthogranuoma (JXG) belongs, represent a heterogenous collection of disorders related to the monocyte/macrophage lineage. The dermal dendrocyte was previously proposed as the cell of origin for JXG on the basis of Factor XIIIa reactivity, a suggestion that does not fully explain the occasional xanthogranulomatous proliferations localizing exclusively to extracutaneous sites. This study applies a panel of recently developed immunohistochemical markers to JXGs and relates the phenotype of this process to new concepts of monocyte/dendritic cell ontogeny. Twenty-seven JXG, ten dermatofibromas (DF), and ten age-matched normal skin specimens were stained using standard immunohistochemistry methods, and all JXGs were fascin+ and CD68+, although 26 of 27 were reactive for HLA-DR, 25 of 27 for Factor XIIIa, 25 of 27 for LCA, 21of 27 for CD4, and 8 of 27 for polyclonal s100. Six of those eight polyclonal S100+ cases were also reactive for monoclonal S100. None of those cases was reactive for CD1a, CD3, CD21, CD34, or CD35. Eight of ten dermatofibromas were FXIIIa+; all were negative for HLA-DR, LCA, CD4, and polyclonal s100. In controls, fascin+ dendritic cells were present but did not stain for Factor XIIIa, S100, or CD4. Based on the morphologic and phenotypic overlap of the lesional cells in JXGs and plasmacytoid monocytes, it would appear that the plasmacytoid monocyte might be considered the putative normal counterpart of the major cellular population of JXGs, a proposal that helps explain the extra-cutaneous, visceral, and soft tissue location that have been reported for occasional cases of JXG. We would also conclude that neither Factor XIIIa-nor S100+ results should preclude the diagnosis of JXG, and find that reactivity for CD4 and LCA may be used to distinguish JXG from DF when the latter is heavily lipidized or the former is not.

On the histologic heterogeneity of thymic epithelial neoplasms. Impact of sampling in subtyping and classification of thymomas

Six hundred thirty cases of thymomas were evaluated to determine morphologic heterogeneity. The thymomas were grouped in 4 categories using previous terminology. Stratification according to the number of sections available for examination revealed a marked difference in distribution by histopathologic type. A cutoff number of 5 sections appears to provide a difference in subgrouping these tumors. In addition, the proportion of invasive tumors increases with the number of sections examined. Final classification may be affected by the extent of sampling. Histopathologic classification of thymoma, although of academic interest, may have limited practical relevance for assessment of prognosis in limited biopsy tissue. Proper evaluation of histology and aggressive potential in thymoma should be based on ample sampling and assessment of capsular integrity, which is best accomplished on thoroughly sampled resection specimens rather than incomplete or limited biopsy samples.

The role of immunohistochemistry in the diagnosis of malignant mesothelioma

The immunohistochemical diagnosis of mesothelioma is perhaps one of the most perplexing and controversial issues in surgical pathology. A tumor that in essence is extremely rare has managed to captivate the attention not only of pulmonologists and thoracic surgeons but also of pathologists. Throughout its history, mesothelioma has emerged as one of the tumors that has evaded definitive characterization; hence, the numerous attempts at trying to establish not only histological criteria but also histochemical, immunohistochemical, and ultrastructural guidelines for its diagnosis. Perhaps as we enter an era of more sophisticated technology, molecular biology will have an opportunity to make inroads into the diagnosis and characterization of this peculiar neoplasm. Despite the many difficulties involved in the diagnosis of malignant mesothelioma, we have recently gained significant knowledge of this entity in many respects, several decades after its description. From a morphological point of view, several variations of the histological appearances that these tumors may exhibit have been described. Traditional histochemistry and electron microscopy continue to play an important role in the evaluation of these neoplasms, with ultrastructural analysis in particular representing the most reliable technique for making this diagnosis in equivocal cases. However, because of its speed, cost-effectiveness, and general availability, immunohistochemistry has emerged as the most commonly used procedure for the diagnosis of mesotheliomas. We herein present a review of the current status of immunohistochemical evaluation of malignant lesions that are suspected of having a mesothelial lineage.

Neuroendocrine carcinomas (carcinoid tumor) of the thymus. A clinicopathologic analysis of 80 cases

We studied 80 cases of primary thymic neuroendocrine carcinomas. Most patients had symptoms; approximately one third were asymptomatic. All cases were treated by surgical excision. The tumors were divided according to histopathologic features into low- (n = 29), intermediate- (n = 36), and high-grade (n = 15) types. The tumors displayed a variegated histologic appearance and unusual cytologic features. Some cases showed transition from low to high grade within the same tumor mass. Mitotic activity ranged from fewer than 3 to more than 10 mitotic figures per 10 high-power fields, and most tumors displayed marked cellular atypia and areas of necrosis. In 73 patients, the tumor was confined to the anterior mediastinum. Positive immunohistochemical reaction was observed using antibodies for CAM 5.2 low-molecular-weight cytokeratins, broad-spectrum keratin, chromogranin, synaptophysin, and Leu-7. The clinical follow-up obtained in 50 patients correlated well with tumor differentiation. Therefore, the behavior of these tumors seems to correlate with histologic grade, which seems directly proportional to degree of differentiation. We propose replacing the term thymic carcinoid with thymic neuroendocrine carcinoma, which better reflects the aggressive biologic behavior of these tumors in the mediastinal location.

Primary neuroendocrine carcinoma (thymic carcinoid) of the thymus with prominent oncocytic features: a clinicopathologic study of 22 cases

Twenty-two cases of oncocytic thymic neuroendocrine carcinomas (carcinoid tumors) are presented. The patients were 17 men and 5 women between the ages of 26 and 84 years (median, 55 years). Nine were asymptomatic, and the tumor was found on routine examination; four patients presented with chest pain, two with weight loss, two with multiple endocrine neoplasia I syndrome, and one with Cushing's syndrome. Surgical resection of the mediastinal tumor was performed in all cases. The lesions were described as soft, light tan to brown, measuring from 3 to 20 cm in greatest diameter. On cut section, the tumors showed a homogeneous surface, soft consistency, and focal areas of hemorrhage. Microscopically, the lesions were characterized by nests or trabeculae of tumor cells that contained abundant granular to densely eosinophilic cytoplasm, with round to oval nuclei and in some areas prominent nucleoli. Mitotic figures ranged from 2 to 10 per 10 high-power fields; foci of comedonecrosis were seen in all cases. Immunohistochemical studies including broad spectrum keratin, CAM 5.2, chromogranin, synaptophysin, Leu-7, and p53 were performed in 12 cases. All of the tumors were strongly positive for CAM 5.2 low-molecular-weight cytokeratin, 11 showed strong positive reaction for Leu-7, 10 for broad-spectrum keratin, 8 for chromogranin, 7 for synaptophysin, and only 1 case showed focal positive staining of the tumor cells for p53. Clinical follow-up of 14 patients showed that 10 were alive between 2 and 11 years, and 4 patients had died of tumor from 4 to 11 years after diagnosis. Patients with good clinical outcome were those whose tumors showed low mitotic activity and minimal nuclear pleomorphism, whereas those who had died of their tumors were those whose tumors were characterized by marked nuclear atypia and higher mitotic rates. Oncocytic thymic carcinoids should be added to the differential diagnosis of anterior mediastinal neoplasms characterized by a monotonous population of tumor cells with prominent oncocytic features.

Thymic neuroendocrine carcinomas with combined features ranging from well-differentiated (carcinoid) to small cell carcinoma. A clinicopathologic and immunohistochemical study of 11 cases

We reviewed 11 cases of primary thymic neuroendocrine carcinomas with combined features ranging from well-differentiated to poorly differentiated neuroendocrine carcinoma. For 3 asymptomatic patients, tumors were discovered during routine examination. Presentation in the other patients was as follows: Cushing syndrome, 2 patients; chest pain, 3 patients; superior vena cava syndrome, 1 patient; and hypercalcemia and hypophosphatemia, 1 patient. No clinical data were available for the 11th patient. All tumors were located in the anterior mediastinum and treated by surgical excision. The lesions were large and well-circumscribed with areas of hemorrhage and necrosis. They were characterized by areas showing a proliferation of monotonous, round tumor cells adopting a prominent organoid pattern admixed with areas showing sheets of atypical cells with hyperchromatic nuclei, frequent mitoses, and extensive areas of hemorrhage and necrosis. Immunohistochemical studies performed in 6 cases showed strong CAM 5.2 low-molecular-weight cytokeratin positivity in all cases, chromogranin and synaptophysin positivity in 4, Leu-7 in 3, and focal positivity for p53 in 2. Follow-up information for 9 cases showed that all patients died of their tumors between 1 and 4 years after diagnosis. The present cases highlight the heterogeneity of neuroendocrine neoplasms and reinforce the notion that these tumors form part of a continuous spectrum of differentiation.

Pigmented thymic carcinoids: a clinicopathological and immunohistochemical study of two cases

Two cases of pigmented thymic carcinoids are presented. The patients were two men, 32 and 47 years of age. The two patients were asymptomatic and the tumor was discovered on routine chest radiographic evaluation. The tumors were treated by surgical excision in both patients. Grossly, they presented as tan-white tumors without evidence of necrosis or hemorrhage or any visible pigmentation. Histologically, the tumors were characterized by a monotonous proliferation of tumor cells arranged in a trabecular or nesting pattern. The tumor cells showed moderate amounts of pale eosinophilic cytoplasm, round to oval nuclei, and inconspicuous nucleoli. Mitotic activity varied from three to eight per 10 high-power fields. In addition, both tumors showed prominent areas of intra- and extracellular dark pigment deposition. The pigment reacted positively with the Fontana-Masson stain and was negative for iron stain. Immunohistochemical studies performed in one case showed immunoreactivity of the tumor cells for chromogranin, Leu 7, and keratin. Synaptophysin and P53 immunostains were negative. Clinical follow-up was obtained in one patient who was alive and well 10 years after surgical resection. The presence of abundant melanin pigment in thymic carcinoids highlights an important pitfall for diagnosis in these tumors that should be taken into consideration in the evaluation of anterior mediastinal lesions.

Micronodular thymoma with lymphoid B-cell hyperplasia: clinicopathologic and immunohistochemical study of eighteen cases of a distinctive morphologic variant of thymic epithelial neoplasm

We describe 18 cases of a distinctive morphologic variant of primary thymic epithelial neoplasm characterized by a micronodular growth pattern associated with florid lymphoid follicular hyperplasia of the stroma. The tumors occurred in seven women and 11 men aged 41 to 76 years (mean, 58 years). All cases were asymptomatic and discovered incidentally on routine chest radiograph or during coronary artery bypass surgery. The tumors measured from 3 to 10 cm in greatest dimension and were well circumscribed and encapsulated. In seven cases, the lesions were grossly described as cystic or partially cystic masses. Histologically, they were characterized by a proliferation of small tumor nodules separated by abundant lymphoid stroma with prominent germinal centers. The nodules were composed of spindle cells containing oval nuclei devoid of atypia or mitotic activity. Immunohistochemical studies showed strong positivity of the spindle tumor cells for CAM 5.2 and broad spectrum keratin antibodies. The surrounding lymphoid cell population was strongly positive for LCA and L26 and showed a polyclonal pattern of staining for kappa and lambda. Stains for UCHL-1, CD1a, CD3, CD5, and CD99 were negative in the stromal lymphoid cell population. The tumor in one of the patients was associated with active pulmonary tuberculosis, and in another with anemia and splenomegaly of unknown etiology. None of the patients had clinical signs or history of myasthenia gravis or other autoimmune disorders. The present cases are interpreted as an unusual morphologic variant of spindle cell thymoma with prominent B-cell lymphoid hyperplasia. The possible significance of this phenomenon is discussed.

Angiomatoid neuroendocrine carcinoma of the thymus: report of a distinctive morphological variant of neuroendocrine tumor of the thymus resembling a vascular neoplasm

Three cases of primary thymic neuroendocrine tumors characterized by prominent angiomatoid features that resembled a vascular neoplasm are presented. The patients were all men between 52 and 59 years of age who presented with chest pain and shortness of breath attributable to a large anterior mediastinal mass. The lesions ranged in size from 6 cm to 15 cm in greatest diameter, and were grossly soft and well circumscribed, but not encapsulated. The cut surface was remarkable for multiple blood-filled cyst-like spaces admixed with focal solid, hemorrhagic areas. Histologically, the tumors contained multiple cystically dilated spaces filled with blood which imparted the lesion with a striking angiomatoid appearance. The walls of the cysts were lined by a monotonous proliferation of round to oval cells with distinct cell borders, round central nuclei, and abundant eosinophilic cytoplasm. Mitotic activity was present in all cases and varied from 3 to 8 mitoses per 10 high-power fields. Immunohistochemical studies performed in two cases showed positivity of the tumor cells for keratin, Leu 7, and synaptophysin, and focal chromogranin positivity in one. Follow-up information obtained in two patients showed that both had died of tumor 4 and 8 years after initial diagnosis. The present cases show an unusual morphological appearance of thymic neuroendocrine tumors that may be mistaken for a vascular neoplasm. Immunohistochemical stains may be of importance in such instances in arriving at the correct diagnosis.

Thymoma, atypical thymoma, and thymic carcinoma. A novel conceptual approach to the classification of thymic epithelial neoplasms

Primary thymic epithelial neoplasms have been the subject of much controversy in recent years owing to the difficulties posed by these tumors for precise histopathologic typing and prognostication. A number of classification schemes using different terminology have been proposed, none of which has satisfactorily managed to address all the problems and concerns related to these tumors. We present a proposal for a novel approach to the histologic classification of primary thymic epithelial neoplasms that is based on morphologic features of differentiation. The principle behind this classification scheme is that the determination of the cytologic degree of atypia and the identification of the organotypical features of thymic differentiation may permit accurate classification of these neoplasms into 3 simple and reproducible diagnostic categories: thymoma, atypical thymoma, and thymic carcinoma. We further reiterate the traditional concept that tumor staging, not histopathologic typing, has a more crucial role for accurate and reliable prognostication for the better differentiated forms of these tumors.

Spindle-cell neuroendocrine carcinomas of the thymus (spindle-cell thymic carcinoid): a clinicopathologic and immunohistochemical study of seven cases

Seven cases of spindle-cell neuroendocrine carcinomas (carcinoid tumors) of the thymus are presented. The patients were three women and four men between the ages of 26 and 74 years (median age, 50 yr). The lesions presented as large anterior mediastinal masses on radiographic examination and were treated by surgical excision. Grossly, the tumors were tan-brown and well circumscribed but encapsulated, and they measured from 2 to 15 cm in greatest diameter. Histologically, they were characterized by a dense proliferation of spindle cells that focally adopted a vaguely organoid pattern, with discrete nests of tumor cells separated by thin fibrovascular septa. Mitotic figures were present in all of our cases and ranged from 2 to 8 per 10 high power fields. Focal areas of necrosis were also present in all of the cases. Immunohistochemical studies performed in six cases showed positive staining for chromogranin in five cases, synaptophysin and keratin in four, and Leu 7 in three. Clinical follow-up showed that two patients died of their tumors 6 and 11 years after diagnosis; one was alive 8 years after diagnosis. Spindle-cell neuroendocrine carcinomas of the thymus (spindle-cell thymic carcinoids) should be considered in the differential diagnosis of spindle-cell neoplasms of the anterior mediastinum. Because of their aggressive clinical behavior, it is important to separate them from the other benign or low-grade spindle-cell tumors that are more common at this location.

Spindle cell thymic carcinoma: clinicopathologic and immunohistochemical study of a distinctive variant of primary thymic epithelial neoplasm

We report 16 cases of a distinctive variant of primary thymic epithelial neoplasm characterized by prominent spindling of the tumor cells. The patients were seven women and nine men aged 23 to 82 years (mean, 54 years). The lesions presented as anterior mediastinal masses without clinical or radiographic evidence of tumor elsewhere. Most patients had chest pain, dyspnea, and cough; in five patients, the tumors were asymptomatic and were discovered on routine clinical examination. Grossly, the lesions were firm, well-circumscribed, and locally infiltrative, and had a firm cut surface with foci of hemorrhage, necrosis, and cystic changes. Most of the tumors were treated by complete surgical excision. Histologically, they were characterized by a spindle cell proliferation showing varying degrees of atypia and mitotic activity. In 12 cases, transitions could be seen with areas that showed the features of conventional spindle cell thymoma. In two cases, areas showing features of poorly differentiated (lymphoepitheliomalike) carcinoma and anaplastic carcinoma could also be observed. Immunohistochemical studies in 10 cases showed strong positivity of the spindle tumor cells for CAM5.2 cytokeratin, and negative staining for a panel of antibodies including epithelial membrane antigen, carcinoembryonic antigen, actin, desmin, vimentin, S-100 protein, HMB45, CD34, CD5, and CD99. Clinical follow-up of eight patients showed an aggressive biologic behavior with recurrence, metastasis, and death by tumor in five of them 2 to 5 years after diagnosis. Based on these findings, the present tumors are interpreted as an unusual spindle cell variant of thymic carcinoma. The close association of these cases with areas showing the features of spindle cell thymoma within the same tumor mass suggests that some of these lesions may arise as a result of malignant transformation in a preexisting spindle cell thymoma.

Idiopathic fibroinflammatory (fibrosing/sclerosing) lesions of the mediastinum: a study of 30 cases with emphasis on morphologic heterogeneity

The clinicopathologic and immunohistochemical findings in 30 cases of idiopathic fibroinflammatory lesions of the mediastinum are presented. There were 17 male and 13 female patients between 10 and 64 years of age; 19 were African-American, and 10 were Caucasian. Clinically, respiratory and/or systemic symptoms including cough, shortness of breath, and fever were present in 28 patients. Five patients also presented with evidence of superior vena cava syndrome. All of the lesions involved the anterior mediastinum with radiographic evidence of hilar and paratracheal involvement in nine and five patients, respectively. Histologically, the lesions were characterized by an inflammatory fibrosing process that showed three distinctive histologic patterns. On the basis of the histologic pattern, they were subdivided into three distinct groups (stages). Stage I demonstrated edematous fibromyxoid tissue with numerous spindle cells, eosinophils, mast cells, lymphocytes, plasma cells, and thin-walled blood vessels; Stage II showed thick glassy bands of haphazardly arranged collagen with focal interstitial spindle cells, lymphocytes, and plasma cells; and Stage III was characterized by dense acellular collagen with scattered lymphoid follicles and occasional dystrophic calcification. Immunohistochemical studies in 17 cases highlighted large numbers of vimentin- and actin-positive spindle cells and capillary-like vessels in Stage I lesions, with fewer numbers of vimentin-positive, actin-negative spindle cells and vessels in Stage II lesions. Our findings suggest that "sclerosing mediastinitis" represents the final stage of an evolving, dynamic process with different morphologic appearances akin to abnormal wound healing. Thus, we propose the term fibroinflammatory lesion of the mediastinum to convey the true nature of the process.

Pulmonary dirofilariasis: a clinicopathologic study of 41 lesions in 39 patients

Forty-one cases of pulmonary dirofilariasis in 39 patients are presented. The patients, all Americans, were between 8 and 80 years old (median, 58 years), including 23 men and 16 women. Twenty-two patients were asymptomatic (56%), and the pulmonary nodule was discovered on chest radiographs during a routine physical examination. Seventeen patients (44%) presented with respiratory symptoms or systemic complaints. Peripheral eosinophilia was noted in only 10% of the patients. Radiographically, most lesions were located in the right lung (76%), with a predilection for the lower lobe. In five patients multifocal nodules were seen. All patients underwent thoracotomy with excisional lung biopsy or lobectomy. Pathologically, all cases featured a histiocyte-rimmed necrotic nodule containing fragments of a partially degenerated Dirofilaria immitis. In addition, adjacent lung parenchyma showed morphological features suggestive of other pulmonary processes such as extrinsic allergic alveolitis and/or pulmonary vasculitis syndromes. Three of the five patients with multiple nodules had solitary dirofilarial nodules and adjacent non-small cell carcinomas. The cases presented herein highlight the variable morphological features seen in human pulmonary dirofilariasis and emphasize the need to consider this diagnosis in all cases of necrotizing granulomas of the lung.

Primary thymic epithelial neoplasms: spectrum of differentiation and histological features

Primary thymic epithelial neoplasms have been the source of much controversy over the years because of difficulties in their histopathologic classification and prognostication of clinical behavior. Despite recent advances in our understanding of the immunopathology and molecular pathology of these neoplasms, no universally accepted system of classification is yet available for these tumors. A variety of classification schemes have been proposed in the past based on either morphological, histogenetic, or immunophenotypic considerations. For the most part, the majority of such classifications have been merely descriptive with little value for prognostication, or have proven cumbersome and difficult to apply in clinical practice. Recent studies have shown that primary thymic epithelial neoplasms, rather than representing several discrete, separate entities constitute part of a continuous spectrum of differentiation ranging from well-differentiated neoplasms to poorly-differentiated neoplasms. Based on these observations, a novel classification of primary thymic epithelial neoplasms has been proposed that divides these tumors into three easily reproducible diagnostic categories based on their degrees of differentiation: thymoma, atypical thymoma, and thymic carcinoma (corresponding to well-differentiated, moderately-differentiated, and poorly-differentiated neoplasms, respectively). The histopathologic features and diagnostic criteria for these tumors is the subject of this review.

Primary neuroendocrine carcinomas of the thymus

Primary neuroendocrine carcinomas of the thymus are rare and comprise a wide spectrum of lesions ranging from well-differentiated to poorly-differentiated neoplasms. The classification of such tumors in the thymus is still controversial. By convention, the better-differentiated examples have been traditionally designated as thymic carcinoids and thought to represent the mediastinal counterpart of carcinoid tumors in other foregut locations. However, recent studies have shown that such neoplasms, when arising in the thymus, exhibit a much more aggressive behavior than those originating at other locations. We therefore consider these lesions to represent fully malignant neoplasms that fall within the spectrum of neuroendocrine carcinomas. The designation of well-, moderately-, or poorly-differentiated thymic neuroendocrine carcinoma is therefore favored for these tumors in the present review. Because such tumors may often adopt unusual morphological appearances, it is important to distinguish them from other more common conditions presenting at this location that may exhibit similar histological features. The clinicopathologic, immunohistochemical, and differential diagnostic features of these tumors in the mediastinum are discussed.

Desmoid tumors of the pleura: a clinicopathologic mimic of localized fibrous tumor

Intrathoracic desmoid tumors of the pleura are unusual tumors that are often clinically and histologically confused with localized fibrous tumor of the pleura or benign neurogenic tumors. We studied four cases of intrathoracic desmoid tumor of the pleura and reviewed the clinical, histopathologic, and immunohistochemical features of the four patients. Two men and two women, ranging in age from 16 to 66 years (mean, 44 yr) comprised the study group. Three patients presented with chest pain and one with shortness of breath. Two patients had a history of associated trauma in the area of the tumor. Three of the lesions were based in the parietal pleura and one in the visceral pleura. Treatment included complete resection (two cases), subtotal resection (one case), and subtotal resection followed by radiation therapy and complete resection (one case). The mean tumor size was 12.5 cm, and all of the tumors exhibited a bosselated, firm, white, cut surface. The histologic features of intrathoracic desmoid tumors were similar to those of desmoid tumors at more conventional sites. Infiltration of the adjacent fat and skeletal muscle was invariably present. The tumor cells were immunoreactive for vimentin, desmin, smooth muscle actin, and muscle-specific actin in three of the four cases and were negative for S-100 protein. Follow-up to date shows stable residual disease at 12 months (one case) and two patients with no evidence of disease at 12 and 96 months, respectively. Intrathoracic desmoid tumors often exhibit clinical and radiographic features similar to localized fibrous tumor of the pleura. They generally have histologic and behavioral characteristics identical to those of desmoid tumors at conventional sites. Like desmoid tumors elsewhere, complete resection with negative margins is vital to prevent local recurrence. Desmoid tumor should be considered in the differential of localized fibrous tumor of the pleura.

Pleuro-pulmonary endometriosis and pulmonary ectopic deciduosis: a clinicopathologic and immunohistochemical study of 10 cases with emphasis on diagnostic pitfalls

The clinical and pathological features of nine cases of pleuro-pulmonary endometriosis and the first case of pulmonary ectopic deciduosis are presented. The patients were all women between the ages of 27 and 74 years (median, 36 years) who presented with symptoms of catamenial pleural pain, shortness of breath, hemoptysis, or radiographically detected lung masses. Clinically, six patients were multiparous, one patient had pelvic endometriosis, and four patients had undergone prior pelvic surgical procedures, including dilatation and curettage. Radiographically, eight patients had pulmonary infiltrates or nodules, and four patients had pneumothorax. Three cases involved the visceral pleura and one case the parietal pleura. The other six cases, including the single case of ectopic deciduosis, involved the lung parenchyma. Histologically, the single or multifocal lesions were well circumscribed or infiltrative, nodular, cystic, or nodulo-cystic, and showed the characteristic features of proliferative or secretory endometrium with numerous mullerian metaplastic changes. Mucin stains were negative in five cases of endometriosis and in the single case of ectopic deciduosis. Immunohistochemical studies were performed in these same six cases using antibodies to epithelial, mesenchymal, vascular, and neuroendocrine markers. The glandular epithelium was decorated with antibodies to pan-cytokeratin, CK7, BER-EP4, ER, and PR, whereas the stromal cells showed positive staining for vimentin, actin, smooth muscle actin, desmin, ER, and PR. Follow-up information obtained in seven patients showed all women without recurrences after 1 to 20 years. The current study highlights the importance of recognizing intrathoracic endometriosis and ectopic deciduosis and properly assessing small biopsy specimens to avoid a misdiagnosis of malignancy.

Primary ependymoma of the mediastinum: a clinicopathologic study of three cases

Primary mediastinal ependymomas are unusual tumors, with only two case reports previously reported in the literature. In this study, we review our experience with three cases of primary mediastinal ependymomas, including the clinical, histopathologic, immunohistochemical, and ultrastructural features. The three patients in this study were white women with a mean age of 50 years (age range, 36 to 71 years). Presenting symptoms were nonspecific; radiographically, all lesions were circumscribed posterior mediastinal masses without evidence of bone involvement. There was no evidence of central nervous system, sacral, or pelvic ependymoma. All tumors were completely resected, ranged in size from 5 to 7 cm (mean, 6 cm), and exhibited glistening pseudocapsules. Two tumors had a solid, tan-gray cut surface and one lesion was cystic with a mural tumor nodule. All neoplasms showed histologic features of conventional cellular ependymomas with perivascular pseudorosettes and occasional true ependymal rosettes. Germ cell components were not present in any case and immunohistochemical analysis showed glial fibrillary acidic protein, S-100, and patchy cytokeratin immunoreactivity in all three cases as well as absence of reactivity for HMB 45, chromogranin, and synaptophysin. Ultrastructural features included multipart "zipper-like" junctions, intracytoplasmic lumina containing microvilli, occasional cytoplasmic basal bodies, and apical cilia. A microscopic metastasis was present in a regional lymph node in one case at the time of resection; however, there is no evidence of recurrence or distant metastasis in any of the cases during the postoperative period (mean length of follow-up, 64 months). Ependymomas rarely occur in the mediastinum and have a predilection for the posterior mediastinum. The paravertebral location, microscopic identification of adjacent sympathetic ganglia, and lack of teratomatous or other germ cell components suggest that mediastinal ependymomas are likely derived from paravertebral ependymal rests. Primary mediastinal ependymomas are characterized by a prolonged and indolent clinical course. Metastasis to regional lymph nodes may occur, but distant metastases are unusual in our experience. Complete surgical excision seems to offer the best chance for long-term survival.

Primary cutaneous synovial sarcoma: a case report

We present a case of synovial sarcoma involving the cutaneous tissue of the knee in an 18-year-old woman. The 2.5 cm tumor was locally excised and recurred six times over the following 24 years. The neoplasm involved the deep dermis with extension into the papillary dermis and superficial subcutis. The tumor was predominantly composed of spindle cells arranged in compact interdigitating fascicles and scattered epithelial nests were seen. Focal myxoid and hemangiopericytoma-like areas as well as numerous mast cells were identified. Spindle cells stained for vimentin, CAM 5.2, and epithelial membrane antigen, whereas epithelial nests only stained for CAM 5.2 and epithelial membrane antigen. Neither component was reactive for antibodies directed against desmin, muscle specific actin, smooth muscle actin, S-100 protein, CD-31, or CD-34. This newly reported location for this morphologically heterogeneous tumor creates potential diagnostic confusion with other primary neoplasms in these areas.