CO2 Laser Vaporization Research Articles

The Internal Energy of Neutral Ethylene Glycol Molecules Created in the Laser Vaporization of Aerosol Particles

Although laser vaporization of aerosol particles plays an important role in aerosol mass spectrometry, relatively little is known about disposal of excess energy in the degrees of freedom of the gas-phase species. A two-laser scheme, in which an infrared laser vaporizes aerosol particles prior to ionization of the vapor plume by a vacuum-ultraviolet laser, permits the determination of the internal energy of the neutral molecules created in laser vaporization. In this work, the fragmentation patterns of vacuum UV (VUV) photoionization mass spectra of ethylene glycol, in conjunction with photoelectron-photoion coincidence (PEPICO) measurements, determines the internal energy of gas-phase molecules created in the CO2 laser vaporization of neat ethylene glycol particles and ethanol particles mixed with trace ethylene glycol. The internal energy ranges from 1300 to 10250 cm-1 for CO2 laser powers between 25 and 112 mJ/pulse. For neat ethylene glycol, the rate with which the internal and kinetic energy grows wi...

A Case of Xanthoma Disseminatum Treated with CO2 Laser Vaporization and High Dose Steroid

A Case of Xanthoma Disseminatum Treated with CO2 Laser Vaporization and High Dose Steroid

Selective Production of Single-Wall Carbon Nanohorn Aggregates and Their Formation Mechanism

Single-wall carbon nanohorn (SWNH) aggregates can be produced by CO2 laser vaporization of carbon, and a single aggregate can take either a “dahlia-like” or “bud-like” form. We found that “dahlia-l...

Thermal vaporization-vacuum ultraviolet laser ionization time-of-flight mass spectrometry of single aerosol particles.

Single aerosol particles of ethylene glycol and oleic acid are vaporized on a heater at temperatures between 500 and 700 K, and the resulting vapor plume is ionized by a 10.5-eV vacuum ultraviolet (VUV) laser. The mass spectra are compared to those obtained by CO2 laser vaporization followed by VUV laser ionization. The relative intensities of the parent and fragment ion peaks are remarkably similar for the two modes of vaporization. A Maxwell-Boltzmann distribution of speeds accurately describes the dependence of the signal as a function of the VUV laser pulse timing. The signal levels obtained with this design are sufficient to obtain good-quality mass spectra.

LASER THERAPY FOR CARCINOMA IN SITU OF THE PENIS

No AccessJournal of UrologyCLINICAL UROLOGY: Original Articles1 Nov 2001LASER THERAPY FOR CARCINOMA IN SITU OF THE PENIS B.P.J. van BEZOOIJEN, S. HORENBLAS, W. MEINHARDT, and D.W.W. NEWLING B.P.J. van BEZOOIJENB.P.J. van BEZOOIJEN More articles by this author , S. HORENBLASS. HORENBLAS More articles by this author , W. MEINHARDTW. MEINHARDT More articles by this author , and D.W.W. NEWLINGD.W.W. NEWLING More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(05)65650-9AboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract Purpose: Carcinoma in situ of the penis, also referred to as Bowen’s disease or erythroplasia of Queyrat, may lead to invasive squamous cell carcinoma. We assessed the results of laser therapy for carcinoma in situ of the penis. Materials and Methods: From 1986 to 2000 we treated 19 patients with carcinoma in situ of the penis with the neodymium:YAG or carbon dioxide laser. Treatment was assessed retrospectively. No patient was lost to followup. Results: No complications developed and cosmesis was excellent. After 2 to 4 months 3 patients (16%) received repeat treatment because of incomplete disappearance of the lesion. Mean followup was 32 months. True carcinoma in situ recurrent in 5 patients (26%) at an average followup of 25 months (range 6 to 75), while 1 had infiltrating carcinoma. All patients with carcinoma in situ underwent repeat laser treatment. Conclusions: In our experience laser therapy is appropriate initial treatment for carcinoma in situ of the penis with excellent cosmetic and functional results. This therapy is also suited for recurrence without the need for more mutilating therapy. However, the high incidence of recurrence indicates the need for careful followup and patient self-examination. References 1 : Precancerous dermatoses: a study of two cases of chronic atypical epithelial proliferation. J Cutan Dis1912; 30: 241. Google Scholar 2 : Erythroplasie du gland. Bull Soc Franc Derm Syph1911; 22: 378. Google Scholar 3 : Carcinoma in situ of penis. Is distinction between erythroplasia of Queyrat and Bowen’s disease relevant?. Urology1990; 36: 479. Google Scholar 4 : Squamous cell carcinoma of the penis: premalignant lesions. Scand J Urol Nephrol2000; 205: 187. Google Scholar 5 : Detection of occult metastasis in squamous cell carcinoma of the penis using a dynamic sentinel node procedure. J Urol2000; 163: 100. Link, Google Scholar 6 : Carcinoma of penis. Review of cases treated by surgery and radiation therapy 1960–1977. Urology1981; 18: 149. Google Scholar 7 : Erythroplasia of Queyrat. A clinicopathologic and histochemical study. Cancer1973; 32: 1396. Google Scholar 8 : The management and prevention of premalignant penile lesions. Scan J Urol Nephrol2000; 205: 220. Google Scholar 9 : Treatment of penile intraepithelial neoplasia (PIN) with interferon alpha-2a, CO2 laser (vaporization) and 5-fluorouracil 5% (5-FU). Eur J Gynaecol Oncol1997; 18: 410. Google Scholar 10 : Squamous cell carcinoma of the penis. III. Treatment of regional lymph nodes. J Urol1993; 149: 492. Link, Google Scholar 11 : Treatment of superficial basal cell carcinoma and squamous cell carcinoma in situ with a high-energy pulsed carbon dioxide laser. Arch Dermatol1998; 134: 1247. Google Scholar 12 : High- and low-power CO2-lasers; comparison of results for three clinical indications. J Reprod Med1993; 38: 455. Google Scholar 13 : Laser therapy of squamous cell dysplasia and carcinoma of the penis. Urology1998; 52: 559. Crossref, Medline, Google Scholar 14 : Sapphire probe laser surgery for localized carcinoma of the penis. Eur J Surg Oncol1988; 14: 193. Google Scholar 15 : Local recurrent tumour after penis-conserving therapy. A plea for long-term follow-up. Br J Urol1993; 72: 976. Google Scholar From the Free University Medical Center and The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands© 2001 by American Urological Association, Inc.FiguresReferencesRelatedDetailsCited byLont A, Gallee M, Meinhardt W, van Tinteren H and Horenblas S (2018) Penis Conserving Treatment for T1 and T2 Penile Carcinoma: Clinical Implications of a Local RecurrenceJournal of Urology, VOL. 176, NO. 2, (575-580), Online publication date: 1-Aug-2006.WINDAHL T, SKEPPNER E, ANDERSSON S and FUGL-MEYER K (2018) SEXUAL FUNCTION AND SATISFACTION IN MEN AFTER LASER TREATMENT FOR PENILE CARCINOMAJournal of Urology, VOL. 172, NO. 2, (648-651), Online publication date: 1-Aug-2004.WINDAHL T and ANDERSSON S (2018) Combined Laser Treatment for Penile Carcinoma: Results After Long-Term FollowupJournal of Urology, VOL. 169, NO. 6, (2118-2121), Online publication date: 1-Jun-2003. (2018) EDITORIAL COMMENTJournal of Urology, VOL. 168, NO. 6, (2421-2421), Online publication date: 1-Dec-2002. Volume 166Issue 5November 2001Page: 1670-1671 Advertisement Copyright & Permissions© 2001 by American Urological Association, Inc.Keywordspenislaserscarcinoma in situMetricsAuthor Information B.P.J. van BEZOOIJEN More articles by this author S. HORENBLAS More articles by this author W. MEINHARDT More articles by this author D.W.W. NEWLING More articles by this author Expand All Advertisement PDF downloadLoading ...

Growth of single-wall carbon nanotubes dependent on laser power density and ambient gas pressure during room-temperature CO2 laser vaporization

Single-wall carbon nanotubes (SWNTs) were synthesized by the irradiation of 20-ms CO2 laser pulses onto a graphite–Co/Ni target at room temperature. We investigated the effect of laser power density (10–150 kW/cm2) and ambient Ar gas pressure (150–760 Torr) on the abundance of SWNTs with lengths of up to about 200 nm in soot-like carbonaceous deposits. For a constant power density (30 kW/cm2), depending on the Ar gas pressure, SWNTs with diameters of 1.2–1.4 nm were synthesized. Expansion behavior and temperature-fall rates of clusters and/or particles in laser plumes were also analyzed by high-speed video imaging and temporally and spatially resolved emission spectroscopy. The temperature-fall rates were estimated to be 171–427 K/ms. The SWNT growth on the time scale of a few milliseconds appeared to be related to some features of condensing clusters and/or particles, including resident densities, collision frequencies and temperatures.

Port-Wine Stain Nodules in the Adult

BACKGROUND Port-wine stain (PWS) is a congenital vascular malformation of the superficial dermal vessels. These vessels become progressively ectatic, with development of nodular and hypertrophic areas on the surface of the lesions. OBJECTIVE To determine the efficacy of CO2 laser vaporization in the treatment of nodules in PWS. METHODS Twenty adult patients with PWS who developed nodules and hypertrophy on the surface of the lesions were treated by CO2 laser vaporization. Only one pass was performed to each area of the lesions, using a continuous and defocused mode, with a power density of 10 W/cm2. When the treated lesion was very large, several sessions of treatment were necessary to vaporize its entire surface. Photographic controls were performed before and after treatment. RESULTS The nodules and hypertrophy were removed and the smooth surface of the lesions was reestablished. The color, usually violaceous, was transformed in a slight erythema. CONCLUSION CO2 laser is a good method for treatment of nodules and hypertrophy in PWS. With adequate precautions, excellent cosmetic results can be obtained. Other more-specific laser systems may be successively used to treat the remaining erythema.

Port-Wine Stain Nodules in the Adult: Report of 20 Cases Treated by CO2Laser Vaporization

Port-wine stain (PWS) is a congenital vascular malformation of the superficial dermal vessels. These vessels become progressively ectatic, with development of nodular and hypertrophic areas on the surface of the lesions. To determine the efficacy of CO2 laser vaporization in the treatment of nodules in PWS. Twenty adult patients with PWS who developed nodules and hypertrophy on the surface of the lesions were treated by CO2 laser vaporization. Only one pass was performed to each area of the lesions, using a continuous and defocused mode, with a power density of 10 W/cm2. When the treated lesion was very large, several sessions of treatment were necessary to vaporize its entire surface. Photographic controls were performed before and after treatment. The nodules and hypertrophy were removed and the smooth surface of the lesions was reestablished. The color, usually violaceous, was transformed in a slight erythema. CO2 laser is a good method for treatment of nodules and hypertrophy in PWS. With adequate precautions, excellent cosmetic results can be obtained. Other more-specific laser systems may be successively used to treat the remaining erythema.

Laser supraglottoplasty for laryngomalacia: are specific anatomical defects more influential than associated anomalies on outcome?

Objective: To evaluate different CO2 laser procedures on children with various types of laryngomalacia and determine the role of associated anomalies on the outcome. Design: Retrospective chart review. Setting: Academic tertiary referral center. Patients: Twenty-three children who underwent laser supraglottoplasty for laryngomalacia between 1991 and 1998 at the UC Davis Medical Center. Interventions: CO2 laser vaporization of redundant supraglottic mucosa of the aryepiglottic fold, arytenoid, and the epiglottis, or modification of the latter, either individually or in combination, based on the obstructing anatomy. Outcome measures: Immediate, short term, intermediate and long term relief of respiratory symptoms, feeding difficulties, effect of associated anomalies on outcome, effect of specific anatomic obstructing site and surgical procedure performed on outcome, and the incidence of complications inherent to the procedure. Results: Children without associated anomalies invariably did very well, with 78% immediately resolving their respiratory symptoms and 100% within a week. Twelve of the 14 patients with unfavorable immediate results ( P<0.01) and all ten with short term unfavorable results ( P<0.05) had neurologic or anatomic associated anomalies. Seven patients, all with associated anomalies, were considered surgical failures ( P<0.05). These patients also had a significantly longer hospital stay ( P<0.01). The presence of associated anomalies was significant ( P<0.01) in determining surgical treatment of reflux or the need for an NG tube in treating feeding problems. The anatomic site of abnormality and the specific procedure performed did not affect the outcome. There were no serious complications inherent to this procedure. Conclusions: Laser supraglottoplasty, in its different modalities, is a safe and effective treatment for all types of laryngomalacia, but children with associated neurologic or anatomic anomalies will have a more complicated immediate and short term course, as well as a significant incidence of failure. Gastroesophageal reflux is an important associated condition that requires investigation in these patients, and in severe cases will merit surgical procedures to manage. The high incidence of associated neuromuscular anomalies suggests that this component has an important role in the etiology of laryngomalacia.

Obstructive sleep apnea syndrome after reconstructive laryngectomy for glottic carcinoma

Obstructive sleep apnea syndrome (OSAS) is characterized by repetitive episodes of partial or complete obstruction of the upper airway during sleep. The obstruction predominantly occurs along the pharyngeal airway but other sites of obstruction have occasionally been described. We report our experience with three patients suffering from OSAS suspected to be of laryngeal origin. OSAS developed after reconstructive laryngectomy for glottic carcinoma and upper airway obstruction seemed to be located in the reconstructed laryngeal area. The three patients were given nCPAP (nasal-continuous positive airway pressure) treatment associated with peroral endoscopic CO2 laser vaporization of the laryngeal edema. After CO2 laser treatment, one patient was able to stop nCPAP treatment. The other two have remained on nCPAP therapy. OSAS may arise in the post-operative period of reconstructive laryngectomy for glottic carcinoma and can be managed by CO2 laser vaporization (laryngeal edema in the reconstructed area) in association with nCPAP treatment.

Factors of recurrence of intraepithelial lesions of the uterine cervix

A retrospective study (1994-1996) of 282 cases of intraepithelial lesions treated in the Gynecology Services of Coimbra University Hospitals and subsequent follow-up (9-45 months). The following parameters were evaluated as recurrence factors: the patient's age, lesion degree, associated HPV infection, treatment type, safety margin in the ablative treatments and interval free of illness. Of the 282 cases, 72.4% (N = 204) corresponded to HSIL and 27.6% (N = 78) to LSIL. The patients' mean was 36.3 +/- 9.1 [19-67] years. The most commonly used treatment types were the LLETZ (large loop excision of the transformation zone) (76.9%) followed by CO2 LASER vaporization (16%) and finally cold-knife conization (7.1%). The safety margins were determined in 184 cases and, on average, were of 3.2 +/- 2.4 [1-10] mm. Forty-four recurrences occurred (15.6%) of which 75% corresponded to HSIL lesions (N = 33) and 25% (N = 11) to LSIL. From the total number of recurrences the association to HPV infection was found in 24 of the cases (54.5%) and 75% of these (N = 19) corresponded to HSIL. The average age in the recurrence group was 38.2 +/- 8.7 [21-53] years and 35.9 +/- 9.2 [19-67] years in the group without recurrences (p > 0.05). In the LSIL group treated with CO2 LASER (N = 32) the recurrence rate was 15.6% versus 13.3% in the group treated with LLETZ (N = 45). In the HSIL that were treated with CO2 LASER vaporization (N = 13) the recurrence rate was 23%; in those treated with LLETZ (N = 172) there were 16.2% recurrences and in the group submitted to cold-knife conization (N = 19) that rate was 10.5%. The total rate of recurrence was 15.6% with the greatest incidence of lesions associated to HPV (p > 0.05). Regarding the particular case of the HSIL, a great number of recurrences with the destructive treatments (CO2 LASER) was observed when compared to the ablative treatments (cold-knife conization or LLETZ).

Cervix uteri lesions and human papiloma virus infection (HPV): detection and characterization of DNA/HPV using PCR (polymerase chain reaction

The prevalence of human papillomavirus (HPV) genotypes was estimated by the polymerase chain reaction (PCR), in archival paraffin was embedded tissues. The case group consisted of 84 women aged 21-67 years (mean, 40 years) who were referred to the Department of Gynaecology (Oncology Centre, Coimbra) with citopathologically abnormal smears. This group was selected from a population of women who had undergone a screening programme (1990/94) in Central Region of Portugal. All these patients (n = 84) had a colposcopic directed cervical biopsy. HPV detection and typing was performed by the PCR method in the Department of Virology (National Health Care Institute, Lisbon). The prevalence of DNA/HPV found, concerning all epithelial cervical lesions studied and classified as squamous intra-epithelial lesions (SIL) and cervical cancer was 97.8%. On the basis of the data presented in this study, it was estimated that there was a statistically significant prevalence of low risk HPV types (HPV 6/11) in low grade SIL, 83.3%, and a statistically significant prevalence of high risk HPV types (HPV 16,18,31,33,51) in high grade SIL, 58.4%, as well as cervical cancer lesions in 100%. We conclude that there was a statistically significant difference between women with low and high grade SIL for HPV infection, with low and high risk HPV types, respectively. The risk factors for cervical cancer investigated (age at first sexual intercourse, multiple sexual partners, parity, use of oral contraceptives) were not associated to statistically significant differences concerning low grade SIL and high grade SIL. The clinical and therapeutic procedures were evaluated for the same five years (1990/94). It may be concluded that there would be no significant difference in clinical procedure for high grade lesions and cervical cancer, in which the treatment had been frequently radical (cone biopsies, simple or radical hysterectomy) and in which the HPV infection persisted frequently and was associated to high risk types (HPV 16 in 50% of these cases). On the other hand, it may be concluded that HPV detection in cervical biopsies, especially for low grade SIL lesions, which were evaluated in this study with a more conservative procedure (clinical evaluation only, punch biopsies, loop diathermy, CO2 laser vaporisation, cone biopsies), could identify women with high risk HPV types who might be at risk of developing dysplasia and cervical cancer.

Bilateral or Unilateral KTP Laser Ovarian Drilling in Polycystic Ovarian Disease

Bilateral or Unilateral KTP Laser Ovarian Drilling in Polycystic Ovarian Disease

Growth dynamics of carbon-metal particles and nanotubes synthesized by CO2 laser vaporization

To study the growth of carbon-Co/Ni particles and single-wall carbon nanotubes (SWNTs) by 20 ms CO2 laser-pulse irradiation of a graphite-Co/Ni (1.2 at. %) target in an Ar gas atmosphere (600 Torr), we used emission imaging spectroscopy and shadowgraphy with a temporal resolution of 1.67 ms. Wavelength-selected emission images showed that C2 emission was strong in the region close to the target (within 2 cm), while for the same region the blackbody radiation from the large clusters or particles increased with increasing distance from the target. Shadowgraph images showed that the viscous flow of carbon and metal species formed a mushroom or a turbulent cloud spreading slowly into the Ar atmosphere, indicating that particles and SWNTs continued to grow as the ejected material cooled. In addition, emission imaging spectroscopy at 1200 °C showed that C2 and hot clusters and particles with higher emission intensities were distributed over much wider areas. We discuss the growth dynamics of the particles and SWNTs through the interaction of the ambient Ar with the carbon and metal species released from the target by the laser pulse.

Evaluation of CO2 Laser Excision or Vaporization for the Treatment of Vulvar Intraepithelial Neoplasia

Objective. Ourobjective was to evaluate the results of laser surgery in patients with vulvar intraepithelial neoplasia (VIN).Methods. From January 1990 to December 1996, 52 patients with histologically proven VIN were treated with CO2 laser vaporization or laser excision. The analysis included anamnestic characteristics, clinical aspects, types of treatment, correlation of the preoperative biopsy with the excised pathologic specimen, and follow-up results.Results. Fourteen women underwent laser vaporization, and 38, laser excision. Of the patients submitted to vaporization, 11 were cured in one session (75%), 1 required two procedures, and 2 other patients, who underwent more treatments, eventually developed invasive squamous cell cancer 5 and 7 years from the initial treatment. The cure rate for laser excision was better, as a single session of treatment was curative in 33 of 38 patients (87%). In 3 cases the pathology report on the excised specimen showed an unrecognized invasive lesion (12%) and the women underwent radical surgery. The 2 remaining patients, both affected by multifocal disease, experienced recurrences and were treated with laser excision 2 and 3 years after the primary treatment, respectively. Symptom relief was obtained in all patients studied with both laser vaporization and excision.Conclusions. Excisional laser surgery is an effective treatment for patients with VIN. In addition, CO2 laser excision allows evaluation of the operative specimen and detection of occult early invasion with good preservation of vulvar morphology; laser vaporization, while retaining good cosmetic results, is less effective in VIN treatment and does not allow evaluation of the surgical specimen.

Subglottic haemangioma: Controversies in management.

To discuss treatment modalities for subglottic haemangioma (SGH). Case report of two children definitively managed by different modalities. Management by CO2 laser vaporization in one child, and laser followed by interferon 2-alpha in the second child were both successful in controlling the SGH without the need for tracheostomy. The stepped-care approach at John Hunter Children's Hospital, Newcastle, New South Wales, is presented. Both laser surgery and interferon can help control SGH. Careful surveillance and interdisciplinary cooperation are essential to achieve a good outcome.

Management of subglottic haemangioma.

Two contrasting methods of treatment for paediatric subglottic haemangioma are presented. Dr Hoeve describes his results using intralesional steroids and short-term intubation, and Dr Froehlich discusses his outcomes with open surgical excision. Mr Bailey then reviews the currently available therapeutic options with special reference to each of the above techniques, and suggests an optimum plan of management given our current state of knowledge. The conclusion is that very small haemangiomas may not require treatment, or may be amenable to CO2 laser vaporization. Medium-sized lesions seem suitable for intra-lesional steroids and intubation, but large ones are probably best managed by primary submucous resection. Very large haemangiomas, and especially those which are circumferential or in which magnetic resonance imaging (MRI) shows extension down into the trachea and/or through the tracheal wall into the surrounding tissues, may be more safely dealt with by performing a tracheostomy and awaiting spontaneous involution.

The use of the CO2 laser in rhinophyma surgery: personal technique and experience, complications, and long-term results.

Rhinophyma is a slowly progressive disfiguring disorder of the nose that represents the end stage of acne rosacea. The cosmetic deformity is often the reason patients seek medical attention. Over the years, many treatment modalities, including dermabrasion, electrocautery, excision and grafting, decortication, and cryosurgery, among others, have been described to treat this condition, but none of them has proved very satisfactory. Special concern about the droplet dispersion of blood in dermabrasion has made this method less acceptable, as it poses a potential risk to health workers. We describe a technique in which this proliferative disorder can be treated, using CO2 laser excision and vaporization. This method provides a very dry surgical field, which allows the sculpting of the hypertrophic areas to be very effective, giving a very satisfactory immediate and long-term cosmetic results.

Carbon dioxide laser ablation of anogenital condyloma acuminata in pediatric patients.

The treatment of anogenital condyloma acuminata in pediatric patients is difficult, with a wide range of treatment strategies that yield variable success. Treatment regimens must consider the patient age, and etiology, location, and severity of lesions. We report our experience using the carbon dioxide (CO2) laser to ablate these lesions. A retrospective review of a single surgeon's series of 17 consecutive patients was performed. A staging system was developed and used to document the extent of disease as related to prognosis, recurrence rates, and treatment options. There were 17 patients (5 males and 12 females). Eleven patients (65%) were treated after failing previous treatment. Perianal disease was noted in 14 of 17 patients (82%). No patients presented with stage I disease, 7 patients (41%) presented with stage II, 5 patients (29%) presented with stage III, and 5 patients (29%) presented with stage IV disease. Recurrence occurred in 4 of 17 patients (23%). Persistent disease occurred in 1 patient (6%). CO2 laser vaporization of anogenital condyloma acuminata in pediatric patients is safe, relatively atraumatic to the child, and associated with favorable recurrence rates. A staging scheme has been proposed in predicting recurrences, complications, and guiding therapy.

Perianal Bowen's disease

Perianal Bowen's disease is an uncommon squamous-cell carcinoma in situ usually treated by surgical excision. There are controversies concerning surgical margin extent, because the disease is likely to recur in nonexcised skin areas of the anal and perianal skin. The aims of this study were 1) to determine the recurrence rate after different surgical treatments and 2) to determine if molecular markers might have a prognostic role in perianal Bowen's disease. Retrospective chart review from 1972 to 1993 of 47 patients with perianal Bowen's disease was undertaken. Follow-up was obtained by office visits and/or phone questionnaire. Immunohistochemical analysis for p53 protein and Ki-67 nuclear antigen was conducted on fixed tissue specimens. Twenty-six patients were treated by wide local excision with microscopic clearance of resection margins, 15 by local excision with only macroscopic clearance of resection margins, 5 by CO2 laser vaporization, and 1 by abdominoperineal resection because of fecal incontinence. Median follow-up for the entire population was 104 (range, 16-273) months. The incidence of local recurrence was 23.1 percent (6/26) after wide local excision, 53.3 percent (8/15) after local excision, and 80 percent (4/5) after CO2-laser vaporization. Recurrence rate estimated by Kaplan-Meier analysis is statistically different (P = 0.002) between radically treated patients (wide local excision/abdominoperineal resection; n = 27) and patients undergoing conservative treatment (local excision/laser vaporization; n = 20). Among patients with recurrence, the median time until recurrence was 38.5 (range, 3-89) months and 41.5 (range, 4-111) months after conservative and radical treatment, respectively. Nine of 20 (45 percent) patients in the conservative group and none of the 27 patients in the radical group had multiple episodes of recurrence (P < 0.001). In addition, 3 of 20 and 0 of 27 patients in the respective groups developed an invasive cancer (P = 0.034). Positive staining for p53 protein was observed in 12 (33.3 percent) of the 36 tissue specimens available for immunohistochemical analysis. Recurrence occurred in 9 of 24 (37.5 percent) patients negative for p53 and in 6 of 12 (50 percent) patients with positive p53 expression (P = not significant). Ki-67 antigen-graded expression from 1+ to 4+ did not reveal any correlation with incidence of recurrence. Recurrence rate did not differ by p53 and Ki-67 results, either in the overall group of 36 patients or stratified by surgical treatment groups. Wide local excision for perianal Bowen's disease leads to a significantly lower recurrence rate than local excision or laser therapy. Follow-up longer than five years is recommended because of the risk of late recurrence. p53 protein and Ki-67 antigen immunohistologic expression may not have a prognostic role in perianal Bowen's disease.