Importance of Dipole Orientation in Electrostatic Aerosol Filtration.

Electrostatic charge is a major part of modern-day aerosol filtration media (e.g., N95 respirators and surgical facemasks) that has remained poorly understood due to its complicated physics. As such, charging a fibrous material has relied on empiricism in dire need of a mathematical foundation to further advance product design and optimization. In this concern, we have conducted a series of numerical simulations to improve our understanding of how an electrostatically charged fiber captures airborne particles and to quantify how the fiber's dipole orientation impacts its capture efficiency. Special attention was paid to the role of Coulomb and dielectrophoretic forces in the capture of particles of different charge polarities (e.g., particles having a Boltzmann charge distribution). Simulation results were compared with the predictions of the popular empirical correlations from the literature and discussed in detail. Predictions of the empirical correlations better agreed with the simulation results obtained for fibers with a dipole perpendicular to the flow direction rather than for fibers with a dipole parallel to the flow. This indicates that such empirical correlations are more suitable for filters charged via contact electrification (friction charging), where the dipoles are mostly perpendicular to the flow direction, and less suitable for corona-charged media, where the fiber dipoles are generally parallel to the flow direction.

Bouveret Syndrome: A rare form of gallstone ileus a case report.

INTRODUCTION AND IMPORTANCE: Bouveret Syndrome, a rare form of gallstone ileus, involves the migration and impaction of a gallstone in the duodenum or stomach, causing gastric outlet obstruction. Early intervention and a comprehensive care plan are essential for favorable outcomes. CASE PRESENTATION: This article presents a case of an 82-year-old female with a history of coronary artery disease and untreated gallstones. The patient experienced nausea, vomiting, and abdominal pain for two weeks. Diagnostic procedures revealed a cholecystoduodenal fistula with a 4 cm stone lodged at the duodenojejunal angle. For our patient the gallstone was moved to the jejunum, followed by enterotomy and a latero_lateral gastroenteroanastomosis. CLINICAL DISCUSSION: The rarity of Bouveret Syndrome and its nonspecific symptoms make diagnosis challenging, necessitating differentiation from other gastrointestinal disorders. Esophagogastroduodenoscopy (EGD) and imaging, such as computed tomography (CT), play crucial roles in diagnosis. In this case, the EGD did not show gallstones up to the second part of the duodenum. Management involves a multidisciplinary approach, with supportive care for stabilization and the primary goal of removing the impacted stone. Treatment options include endoscopic, surgical, or lithotripsy techniques. Bouveret Syndrome poses challenges due to its rarity, leading to delayed diagnosis. Prognosis varies based on factors such as stone size, location, and overall patient condition. CONCLUSION: Through this case we emphasizes the importance of awareness, timely diagnosis, and appropriate management, with EGD and CT scan playing key roles in diagnosis. Surgical intervention remains a viable treatment option when endoscopic approaches are unavailable. The article highlights the controversial nature of fistula repair in Bouveret Syndrome.

Septic shock revealing boerhaave's syndrome a case report.

INTRODUCTION AND IMPORTANCE: Boerhaave's syndrome, recognized as spontaneous esophageal rupture, is an uncommon and perilous medical condition marked by the spontaneous tearing of the esophagus. This paper highlights the importance of an early diagnosis and its correlation to better outcomes for a rare pathology with high mortality. CLINICAL PRESENTATION: A 67-year-old female presenting with unexplored vomiting and hypertension, presented to the ER with a septic shock. The patient's clinical deterioration prompted emergency exploration, revealing a dilated esophagus with a 3-cm perforation. Despite surgical intervention, including suturing with a T-tube and esophageal exclusion, the patient succumbed to multiorgan failure. CLINICAL DISCUSSION: Boerhaave's syndrome, triggered by forceful vomiting, presents diverse clinical manifestations, making accurate diagnosis challenging. The characteristic triad of vomiting, pain, and subcutaneous emphysema is observed in a minority of cases, often overshadowed by acute respiratory distress. Diagnostic modalities include chest X-rays, contrast esophagography, and computed tomography, aiding in visualizing contrast leakage and confirming the diagnosis. The choice of surgical technique, ranging from esophageal suturing to esophagectomy, depends on the duration between rupture and surgery initiation. In this case, a bipolar esophageal exclusion was performed due to the patient's critical condition. CONCLUSION: Boerhaave's syndrome demands consideration in patients presenting with thoracic pain and vomiting, particularly in those with a pathological esophagus. Early diagnosis and surgical intervention remain pivotal in improving outcomes. Identification of hydro-pneumothorax in radiographic studies should prompt consideration of spontaneous esophageal rupture, highlighting the need for heightened clinical suspicion in nonspecific clinical scenarios.

Primary giant hydatid cyst of the retroperitoneum: Diagnosis and therapeutic approaches.

INTRODUCTION AND IMPORTANCE: Primary hydatid cyst of the retroperitoneum is an exceedingly rare manifestation of hydatid disease. Diagnosis proves challenging due to nonspecific symptoms, and the condition is typically not suspected when facing a retroperitoneal cystic mass, necessitating awareness among clinicians and surgeons, particularly in endemic regions. CASE PRESENTATION: A 45-year-old male with a three-month history of progressive abdominal enlargement and pain. Living in a rural area, he exhibited a 30 cm, well-defined retroperitoneal cyst, with no guarding confirmed by CT-scan, with characteristic daughter cysts. The diagnosis of primary retroperitoneal hydatid cyst was supported by positive hydatid serology and eosinophilia. Surgical intervention was crucial, and a complete pericystectomy, with 4 cm of pericyst on the aorta due to safety concerns, was performed after three months of preoperative albendazole-based treatment. The postoperative course was uneventful, and a two-year follow-up revealed no recurrence. CLINICAL DISCUSSION: The prevalence of hydatid disease in North Africa is high, yet retroperitoneal cases are rare. The difficulty to diagnosis retroperitoneal masses, underscores the importance of precise patient evaluation and detailed imaging analysis. Percutaneous puncture is contraindicated due to the risk of dissemination, highlighting even more the significance of accurate preoperative diagnosis. Surgery, coupled with Albendazole treatment, remains the gold-standard, associated with meticulous intraoperative precautions to prevent disease dissemination. CONCLUSION: Primary retroperitoneal hydatid cyst is rare. Diagnosis is difficult. Precise determination of patient's background and detailed analysis of imaging findings are mandatory. Percutaneous puncture is forbidden as it leads to disease spreading or even anaphylactic shock. Surgical excision is the gold-standard.

Intrauterine device migration resulting in acute appendicitis: A case report.

INTRODUCTION AND IMPORTANCE: The Intrauterine Contraceptive Device (IUD), a widely used contraceptive since 1965, has demonstrated efficacy but is associated with complications such as bleeding, pain, and rare occurrences of perforation. This case report details an IUD migration into the peritoneal cavity, leading to acute appendicitis. CASE PRESENTATION: A 33-year-old woman, with a history of IUD insertion 16 months prior, presented with pelvic pain. Gynecological examination and computed tomography, revealed the IUD intraperitoneal migration. The patient underwent laparoscopic extraction of the IUD which was embedded in the appendix and appendectomy, with an uneventful recovery. CLINICAL DISCUSSION: This case emphasizes the complexity of IUD migration and its rare association with acute appendicitis, underscoring the importance of vigilant monitoring and prompt intervention. We also explored factors contributing to IUD perforation risk, imaging modalities for detection, and emphasizes the necessity of surgical removal upon confirmation. We highlight the fact that despite the atypical presentation with minimal symptoms, we should always consider emergency situations. Surgical intervention, particularly laparoscopy, may be the standard approach for managing migrated IUDs. CONCLUSION: We insist about the critical need for thorough assessment and vigilance in managing IUD-related complications, emphasizing timely intervention to ensure patient safety. This case contributes valuable insights into the complexities surrounding IUD migration, urging healthcare professionals to remain attentive to potential injuries in patients with a history of IUD insertion and abdominal pain.

Pleural migration of biliary stent 10 years following treatment of hepatic hydatic echinococcosis: A case report.

INTRODUCTION: Echinococcosis, caused by larval stages of taeniid cestodes, primarily affects the liver and is commonly treated surgically. However, a complication post-treatment is biliary fistula, necessitating interventions like biliary stents. While stent complications are recognized, proximal migration leading to pneumonia is exceptionally rare. This case report details an unusual occurrence of biliary stent migration years after hepatic hydatid echinococcosis treatment. CASE PRESENTATION: A 42-year-old patient underwent 2014 surgery for a large hydatid cyst, resulting in a biliary fistula. Endoscopic sphincterotomy and biliary stent placement led to a successful outcome. Lost to follow-up, the patient reappeared in 2022 with basithoracic pain, fever, and a thoracic CT scan revealing transdiaphragmatic stent migration causing basal pneumonitis. Antibiotic therapy and endoscopic stent removal ensued with an uncomplicated recovery. CLINICAL DISCUSSION: This report emphasizes a rare complication that is proximal migration of a biliary stent 10 years post-initial placement for biliary fistula management. Despite the absence of typical risk factors. We managed a successful endoscopic retrieval. This highlights the importance of vigilance and follow-up for potential complications associated with biliary stent. Unusual presentations, like pneumonitis, underscore the need for awareness and a cautious approach. CONCLUSION: The primary complication following surgical intervention for hepatic hydatid cysts is the development of an external biliary fistula, necessitating the use of biliary stents for treatment. Given the rarity of complications observed in our case, the removal of stents post-treatment for biliary fistula becomes crucial, underscoring the significance of vigilant follow-up care.

Surgical management of a proximal splenic artery aneurysm: A case report.

INTRODUCTION AND IMPORTANCE: Splenic artery aneurysms (SAA's) pose a rare yet clinically significant challenge, characterized by the weakening and ballooning of the splenic artery, potentially leading to severe complications such as rupture and hemorrhage. CASE PRESENTATION: A 52-year-old female presenting with biliary colic. Diagnostic imaging revealed a saccular lesion closely associated with gallstones. A multidisciplinary approach guided the decision for surgery due to the size and location of the aneurysm. A bi sub costal laparotomy was performed, after the resection of the aneurysm, an arterial anastomosis with pds 5/0 suture was performed. CLINICAL DISCUSSION: SAA's treatment modalities are tailored based on aneurysm localization and size. Imaging modalities such as Doppler ultrasound and CT angiography play a crucial role in accurate diagnosis, providing essential information for treatment planning. Treatment options include endovascular embolization, and surgical intervention. Traditionally open surgical techniques, including ligation of the splenic artery, aneurysmectomy, and splenectomy. Surgical treatment, especially for proximal aneurysms, is highlighted, with the presented alternative approach of resection with end-to-end anastomosis, showcasing an alternative surgical technique aimed at reducing the risk of spleen infarction. CONCLUSION: SAA's are a rarity that emphasizes the need for early detection and intervention. We are urged to maintain a high index of suspicion, particularly in high-risk individuals. We report an alternative surgical technique that we hope will contributes to the expanding repertoire of approaches, calling for further research to optimize SAA management strategies in the quest for improved patient outcomes.

Expression of the soluble vascular endothelial growth factor receptor-1 in cutaneous melanoma: role in tumour progression.

BACKGROUND: Vascular endothelial growth factor (VEGF)-A, placenta growth factor (PlGF) and their corresponding membrane receptors are involved in autocrine and paracrine regulation of melanoma growth and metastasis. Besides the membrane receptors, a soluble form of the VEGF receptor (VEGFR)-1 (sVEGFR-1) has been identified, that behaves both as a decoy receptor, sequestering VEGF-A and PlGF, and as an extracellular matrix (ECM) molecule, promoting endothelial cell adhesion and migration through the interaction with α5ß1 integrin. OBJECTIVES: To analyse whether sVEGFR-1 plays a role during melanoma progression. METHODS: sVEGFR-1 expression was evaluated in a panel of 36 melanoma cell lines and 11 primary human melanocyte cultures by quantitative real-time polymerase chain reaction analysis and in specimens of primary or metastatic melanoma lesions from 23 patients by immunohistochemical analysis. RESULTS: sVEGFR-1 expression was highly upregulated in melanoma cell lines with respect to human melanocytes. Interestingly, cell lines obtained from cutaneous metastases showed a significant reduction of sVEGFR-1 expression, as compared with cell lines derived from primary tumours. These results were confirmed by immunohistochemical analysis of sections from primary skin melanomas and the corresponding cutaneous metastases, suggesting that modulation of sVEGFR-1 expression influences ECM invasion by melanoma cells and metastasis localization. Moreover, we provide evidence that adhesion of melanoma cells to sVEGFR-1 is favoured by the activation of a VEGF-A/VEGFR-2 autocrine loop. CONCLUSIONS: Our data strongly suggest that sVEGFR-1 plays a role in melanoma progression and that low sVEGFR-1/VEGF-A and sVEGFR-1/transmembrane VEGFR-1 ratios might predict a poor outcome in patients with melanoma.

Downregulation of 14-3-3sigma prevents clonal evolution and leads to immortalization of primary human keratinocytes.

In human epidermal keratinocytes, replicative senescence, is determined by a progressive decline of clonogenic and dividing cells. Its timing is controlled by clonal evolution, that is, by the continuous transition from stem cells to transient amplifying cells. We now report that downregulation of 14-3-3sigma, which is specifically expressed in human stratified epithelia, prevents keratinocyte clonal evolution, thereby forcing keratinocytes into the stem cell compartment. This allows primary human keratinocytes to readily escape replicative senescence. 14-3-3sigma-dependent bypass of senescence is accompanied by maintenance of telomerase activity and by downregulation of the p16(INK4a) tumor suppressor gene, hallmarks of keratinocyte immortalization. Taken together, these data therefore suggest that inhibition of a single endogenous gene product fosters immortalization of primary human epithelial cells without the need of exogenous oncogenes and/or oncoviruses.

Nemaline rod myopathy: a rare form of myopathy.

Nemaline rod myopathy (NM) is a rare form of congenital myopathy characterized by slowly progressive or nonprogressive muscle weakness and pathognomonic rod-like structures within the muscle fibers. To the best of our knowledge, this is first documentation of the clinicopathological features of this rare entity from India. All cases of NM diagnosed in our laboratory were retrieved. Clinical and pathological features were reviewed. During a period of 1.5 years (Jan 2004 to June 2005), we received 750 muscle biopsies for various reasons. Of which, 15 were diagnosed as congenital myopathies and four as nemaline rod myopathies. Thus, NM comprises 0.53% of all muscle diseases and 22.6% of all congenital myopathies. All of them presented in childhood (first five years of life) with generalized hypotonia, feeding problems, repeated respiratory infections and muscle weakness. Both males and females were equally affected. The CPK levels were normal and EMG was myopathic. Microscopic examination revealed minimal changes but characteristic red-colored material was seen on modified Gomori trichrome staining which was immunopositive to alpha actinin. Ultrastructural examination confirmed this material to be nemaline rods. NM, although a rare form of congenital myopathies, should be suspected in children who present with generalized hypotonia, repeated chest infections and slowly progressive muscle weakness. This report highlights the importance of histochemistry and ultrastructural examination in the diagnosis of this entity, in the absence of the availability of methodology for genetic studies.

Adult intussusceptions: Clinical presentation, diagnosis and therapeutic management.

BACKGROUND: Adult intussusception is a rare clinical entity. It is an uncommon cause of intestinal obstruction in adult. It often presents with nonspecific symptoms and preoperative diagnosis remains difficult. The purpose of this study was to determine the clinical entity and surgical approach of adult intussusception. METHODS: We have conducted a retrospective descriptive study starting from 2006 until 2014. We reviewed data for all patients that had been admitted to our department for intestinal intussusception. RESULTS: Eight consecutive patients were admitted to our department. The mean age was 48 years old (20-71). The sex ratio was 0,6. The clinical presentation was acute in 5 cases. A computed tomography was performed in 6 cases. The diagnosis of gastrointestinal intussusception was made preoperatively in 100% of patients. All patients underwent surgery. An organic lesion was identified in 100% of the cases. In all cases, resection of the intussuscepted intestinal loop was done without intestinal reduction. All patients were well followed up and recurrences have been documented. CONCLUSION: In adults, intussusception is usually secondary to an organic cause. In the absence of signs of severity, etiologic diagnosis based on CT allows the diagnosis of the intussusception and sometimes can detect the causal lesion. Therapeutic sanction of intussusception is surgery and there is more emphasis towards resection without reduction.

Phenotypic analysis of hMSH2 mutations in mouse cells carrying human chromosomes.

Conversion of diploidy to haploidy is a method that allows the generation of stable murine/human hybrid cell lines carrying selected human chromosomes in only a single copy. In this setting, it is possible to detect genetic mutations with greater sensitivity and reliability than in diploid cells. Using this method, we were able to identify mutations in the human mismatch repair (MMR) gene hMSH2 in hereditary nonpolyposis colon cancer families, which have escaped detection by the conventional methods. In this report, we show that such hybrid cell lines can also be a valuable tool in the study of the mutated MMR proteins, in particular the variants found in hereditary nonpolyposis colon cancer families that carry missense mutations and where it is unclear whether they predispose to colon cancer. This analysis is made possible by the fact that the human hMSH2 protein is able to complement the MMR defect in the host murine cell line.

O6-alkylguanine-DNA alkyltransferase attenuates triazene-induced cytotoxicity and tumor cell immunogenicity in murine L1210 leukemia.

Methylating and chloroethylating triazene compounds (TZCs) are effective antitumor agents in murine leukemias and can induce the appearance of novel antigens in leukemic cells (chemical xenogenization). Recently, it has been shown that TZCs might have a role in the treatment of patients affected by acute myelogenous leukemias that express low levels of the DNA repair enzyme, O6-alkylguanine-DNA alkyltransferase (OGAT). In this report, we have evaluated the role of this DNA repair enzyme in the leukemic cell response to the xenogenizing and cytotoxic properties of TZCs. OGAT-deficient murine leukemic L1210 cells were transfected with a recombinant ecotropic retrovirus containing the coding region for the human OGAT protein. Selected clones expressed the human OGAT transcript and had greatly increased OGAT activity. Compared to OGAT-deficient cells, OGAT-expressing cells were considerably more resistant to the xenogenizing properties of 1-(p-chlorophenyl)-3,3- dimethyl-triazene, measured in terms of leukemia graft rejection, and were less susceptible to the cytotoxic activity of the TZCs 8-carbamoyl-3-methyl-imidazo [5,1-d]-1,2,3,5-tetrazin-4(3H)-one and 8-carbamoyl-3-(2-chloroethyl)imidazo [5,1-d]-1,2,3,5-tetrazin-4(3H)-one. These data suggest that methylation of the O6 position of guanine is involved in the appearance of increased tumor immunogenicity after exposure to methylating TZC and that OGAT is able, at least in part, to counteract the cytotoxic effects of methylating and chloroethylating agents.

Effect of lonidamine on the energy metabolism of Ehrlich ascites tumor cells.

The action of Lonidamine [1-(2,4-dichlorobenzyl)-1-H-indazol-3-carboxylic acid] on oxygen consumption and the rate of aerobic and anaerobic lactate production by Ehrlich ascites tumor cells has been investigated. The rate of oxygen consumption decreases exponentially with the increase of Lonidamine concentration, with maximal inhibition occurring at 0.40 mM Lonidamine. The rate of aerobic lactate production is inhibited to the same extent as is the oxygen consumption. However, the maximum effect is observed at 0.12 mM Lonidamine, and the decrease is linear with Lonidamine concentration. Anaerobic lactate production is more sensitive to Lonidamine, and complete inhibition can be observed by raising the concentration to 0.6 mM. The possibility that the decrease observed in lactate production was secondary to the inhibition of sodium- and potassium-containing adenosinetriphosphatase was excluded, because the drug has no effect on this enzyme. Mitochondrial adenosinetriphosphatase was not affected. Lonidamine was, however, shown to inhibit the activity of mitochondrially bound hexokinase to approximately the same extent as it inhibited aerobic glycolysis (approximately 70%). It is concluded that inhibition of the glycolysis of Ehrlich ascites tumor cells by Lonidamine results from an effect of the drug on the mitochondrially bound hexokinase.

Triazene compounds induce apoptosis in O6-alkylguanine-DNA alkyltransferase deficient leukemia cell lines.

Previous studies demonstrated that triazene compounds (TZC) possess antitumor, antimetastatic and immunosuppressive activity, and induce novel antigenic properties in neoplastic cells. Moreover, TZC showed marked antitumor activity in patients with acute myelogenous leukemias (AML). In most cases leukemic blasts with low levels of the repair enzyme O6-alkyl-guanine-DNA alkyltransferase (OGAT) were highly susceptible to TZC. Therefore the cytotoxic effects of TZC against human leukemic cells and the influence of OGAT modulation were investigated. Five leukemia cell lines were treated with the in vitro active derivative of dacarbazine: 5-(3-methyl-1-triazeno) imidazole-4-carboxamide (MTIC), or with temozolomide (TZM), which is readily cleaved to form the linear triazene MTIC in aqueous solution. The results showed that treatment with TZC at concentrations ranging between 62.5 and 250 microM significantly inhibited cell growth of U-937 and K-562 leukemia cell lines, both with undetectable OGAT activity. Growth inhibition was accompanied by DNA fragmentation and reduction of cell volume characteristic of cell undergoing apoptosis. In contrast, Daudi, HL-60 and Jurkat leukemia cell lines, characterized by high levels of the repair enzyme, were resistant to concentrations of TZC up to 500 microM. Treatment of resistant lines with O6-benzylguanine (BG, a specific inhibitor of OGAT) rendered HL-60 and Daudi but not Jurkat cells sensitive to cytotoxic effects and apoptosis mediated by MTIC. The results presented suggest that: (1) apoptosis is involved in cytotoxic activity of TZC; (2) OGAT could have a role in preventing programmed cell death induced by TZC; and (3) treatment with BG could potentiate cytotoxic and apoptotic effects of TZC on leukemic cell lines when high level of OGAT activity is the main factor involved in resistance to TZC.

In vitro infection of CD4+ T lymphocytes with HTLV-I generates immortalized cell lines coexpressing lymphoid and myeloid cell markers.

The human T cell leukemia/lymphoma virus (HTLV-I) is the etiologic agent of adult T cell leukemia (ATL). CD4+ lymphocytes are the preferential targets of infection, even though other cell types can be infected in vitro by the virus. Although ATL cells show CD3 and CD4 surface markers, some ATL-derived cell lines were reported to express also myeloid antigens. In order to analyze possible phenotypic changes induced by HTLV-I after infection of human lymphocytes, CD4+ cells were isolated from peripheral blood of three healthy donors, by separation through immunomagnetic beads. CD4+ lymphocytes were then infected by coculture with irradiated HTLV-I producing MT-2 cells. The phenotypic profile of infected cells was studied by flow cytometric analysis using monoclonal antibodies against lymphoid (CD3, CD4, TCR alpha/beta) and myelomonocitic markers (CD13, CD14, CD15, CD33, CD34). The results show that HTLV-I immortalized cell lines coexpressed CD13, CD33 and lymphoid markers. No expression of CD14, CD15 and CD34 was observed. These data suggest that the presence of both myeloid and lymphoid phenotype in HTLV-I infected T cells is the results of an induction rather than a selection mechanism.

In vitro infection of leukemic bone marrow with HTLV-I generates immortalized cell lines expressing T or myeloid cell phenotype.

Leukemic bone marrow cells ( > 90% blasts) of a patient with acute myeloblastic leukemia (AML), non-treated or pretreated in vitro with a mutagenic triazene compound, were infected with HTLV-I by coculture with irradiated virus-donor cells. Immortalized, HTLV-I+, double-positive CD4/CD8 euploid T cell lines, expressing HLA class I/II monomorphic determinants, and inappropriate myeloid and progenitor cell markers (ie CD13, CD14, CD15 and CD33 antigens) were obtained. In one out of 10 triazene-pretreated samples, HTLV-I infection resulted in the appearance of a rapidly growing triploid cell line (ie MTLC1 line) showing: (1) myeloid but not lymphoid phenotype; (2) beta and delta T cell receptor in germline configuration; (3) integrated, complete and incomplete HTLV-I provirus genome (also detected in a number of MTLC1 clones); (4) a high percentage of cells positive for non-specific cross-reacting antigen (a CEA-related molecule present in myeloid cells) under the influence of gamma-interferon; (5) absence of HLA class I/II antigen expression; (6) absence of tax gene transcription. Blast cell proliferation was marginal or absent when leukemic marrow was not subjected to retroviral infection. These results show that exposure of leukemic bone marrow to HTLV-I can be followed by immortalization of T and myeloid cells. Although no data are available to establish whether tax expression played a role in the early phase of the immortalization process of MTLC1 line, tax gene product was not required for maintaining long-term growth of MTLC1 cells.

Progressive increase in telomerase activity from benign melanocytic conditions to malignant melanoma.

The expression of telomerase activity and the in situ localization of the human telomerase RNA component (hTR) in melanocytic skin lesions was evaluated in specimens from sixty-three patients. Specimens of melanocytic nevi, primary melanomas and subcutaneous metastases of melanoma were obtained from fifty-eight patients, whereas metastasized lymph nodes were obtained from five patients. Telomerase activity was determined in these specimens by using a Polymerase Chain Reaction-based assay (TRAP). High relative mean telomerase activity levels were detected in metastatic melanoma (subcutaneous metastases = 54.5, lymph node metastases = 56.5). Much lower levels were detected in primary melanomas, which increased with advancing levels of tumor cell penetration (Clark II = 0.02, Clark III = 1.1, and Clark IV = 1.9). Twenty-six formalin-fixed, paraffin-embedded melanocytic lesions were sectioned and analyzed for telomerase RNA with a radioactive in situ hybridization assay. In situ hybridization studies with a probe to the template RNA component of telomerase confirmed that expression was almost exclusively confined to tumor cells and not infiltrating lymphocytes. These results indicate that levels of telomerase activity and telomerase RNA in melanocytic lesions correlate well with clinical stage and could potentially assist in the diagnosis of borderline lesions.