Detection of human papillomavirus-6 in primary carcinoma of the urethra in men

5-aminolevulinic acid photodynamic therapy and holmium laser treatment for intraurethral condylomata acuminata in a renal transplant patient

Condylomata acuminata (CA) caused by human papillomavirus, often involves the external genitalia, perianal skin, and other moist mucous membranes. Urethral involvement is uncommon and little recognized, and usually limited to the distal 3 cm of the meatus. It is difficult to treat CA involving the urethra because of the anatomical location, risk of complications and recurrence. One effective method for the treatment of CA located at the urinary meatus is 5-aminolevulinic acid photodynamic therapy (ALA-PDT). However, experience of using this method for the treatment of whole urethral CA is still very limited. Herein, we treated a whole urethral CA successfully with photodynamic and holmium laser therapies. The case of a 25-year-old patient who underwent kidney transplant effected by intraurethral CA is presented and discussed. Catheter implantation and (or) immunosuppression treatment increases the risk of urethral condyloma acuminatum. The ALA-PDT is a safe, straightforward, effective, and well-tolerated treatment procedure for intraurethral CA. ALA-PDT combined with holmium laser treatment can successfully treat kidney transplant patients with intraurethral CA.

Urethral cancer managed with phallus preserving surgery: a case report

Background

Primary urethral carcinoma (PUC) is rare and accounts for < 1% of all genito-urinary cancers. There is a male predominance of 3:1 and a peak incidence in the 7th and 8th decades. The aetiology of this cancer is similar to penile cancer, and the human papilloma virus (HPV) is thought to be an essential factor in tumorigenesis. Urethral cancer should be diagnosed and staged with a combination of tumour biopsy, MRI, and CT with treatment involving a multimodal approach. Contemporary management emphasises phallus-preserving surgery where feasible.

Case presentation

Here, we describe a case of distal urethral carcinoma, which presented as a metastatic groin mass and identifying the primary lesion proved challenging. Diagnostic flexible cystoscopy identified a tiny lesion in the navicular fossa, which was biopsied and confirmed to be a squamous cell carcinoma. The patient then underwent phallus preserving surgery, including distal urethrectomy with bilateral inguinal lymph node dissections. The final stage was pT1N1M0, and adjuvant chemotherapy was started. The distal urethrectomy involved the surgical creation of a hypospadic meatus in the midshaft of the penis. Normal voiding and sexual function were preserved.

Conclusions

Urethral cancer is a rare malignancy and clinicians should bear in mind that early diagnosis of this disease can be very difficult depending on the anatomical location of the tumour. Treatment currently favours penis-preserving surgery.

Condyloma Acuminata of the Urethra in a Male Renal Transplant Recipient: A Case Report

BACKGROUND

Condyloma acuminatum (CA) is a common sexually transmitted disease associated with human papilloma virus (HPV). CA occurring in the urethra is rare and has not been reported in male renal transplant recipients. In addition, despite immunosuppressive conditions and increased risk of HPV-related malignant neoplasms in transplant recipients, HPV testing in male transplant recipients has been uncommon. Here we report a case of urethral CA in a male deceased donor renal transplantation recipient and discuss the importance of HPV testing in male transplant recipients.

CASE PRESENTATION

A 33-year-old male deceased donor renal transplant recipient presented with miction pain 5 years after the transplantation. He reported repeated urinary tract infections with no sexual contact since the renal transplantation. Multiple papillary tumors in his penile urethra were detected by cystoscopy, and a biopsy sample was pathologically diagnosed with CA. Transurethral tumor resection was performed, and the tumors were completely resected. Additional HPV risk type screening with a urethral smear sample showed the prevalence of low-risk HPV. Although tacrolimus was switched to everolimus and imiquimod cream was administered, the tumors recurred 6 months after the resection, and a second resection was performed. No further recurrence has been observed for 1 year to date.

CONCLUSION

As the urethral CA was possibly related to immunosuppressive conditions and a risk for HPV-related malignant neoplasm, the case required careful diagnosis, including HPV risk type. The methodology of sampling for HPV testing in men has not been established. This case suggests the necessity for further discussion about HPV testing in male transplant recipients.

The contemporary management of primary urethral carcinoma

Primary urethral cancer is a rare malignancy; the most common histological subtype is squamous cell carcinoma. The aetiology of this cancer is similar to penile cancer and the human papilloma virus (HPV) is thought to be an important factor in tumourigenesis. Surgery with or without chemoradiotherapy is the accepted treatment for primary urethral cancer. Current practice supports penile-sparing surgery, to maximise functional and psychological outcomes. We have reviewed the literature to summarise the pathogenesis and management of primary urethral cancer.

Incidence of Low Risk Human Papillomavirus in Oral Cancer: A Real Time PCR Study on 278 Patients

Squamous cell carcinoma is the most frequent malignant tumour of the oral cavity. It is widely known that tobacco and alcohol consumption are the major causes of the development of oral squamous cell carcinoma (OSCC). The human papilloma virus infection has also been postulated as a risk factor for squamous cell carcinoma, although conflicting results have been reported. The aim of this study is to evaluate the presence of high-risk and low-risk type human papillomavirus in a large sample of squamous cell carcinoma limited to the oral cavity by means of quantitative real-time polymerase chain reaction. Data were obtained from 278 squamous cell carcinoma limited to oral cavity proper. Sequencing revealed that 5 samples were positive for HPV type 16, 5 for HPV type 11, and 1 for HPV type 6. Human papillomavirus 11 was detected in 5 tumours out of the 278 examined. The prevalence rate for Human papillomavirus 11 was 1.8% (C.I. 0.7–3.9). The matched case-controls analysis indicated that the prevalence among controls did not significantly differ with respect to cases and that Human papillomavirus 11 alone did not correlate with squamous cell carcinoma.

The role of human papillomavirus infection in prostate carcinoma

Human papillomavirus (HPV) infections are associated with benign and malignant lesions of the female and male anogenital tract. Currently the possible role of HPV infections in prostate carcinogenesis is a subject of great controversy. In this study we aimed to investigate the role of HPV infection in prostate carcinoma (PCa). The study included formalin-fixed paraffin-embedded tissue samples of 104 primary prostate adenocarcinoma cases and 104 control tissues of benign prostatic hyperplasia (BPH). HPV-DNA was purified and amplified through MY09/MY11 and GP5(+)/GP6(+) primers and subsequently subjected to sequencing. HPV-DNA was found in 13 of 104 (12.5%) PCa and 8 of 104 (7.7%) BPH samples. High-risk HPVs were detected in 10 of 13 (76.9%) PCa and 5 of 8 (62.5%) BPH samples with positive HPV-DNA. Low-risk HPVs were detected in 3 of 13 (23.1%) PCa and 3 of 8 (37.5%) BPH specimens with positive HPV-DNA. There was no significant difference between PCa and BPH specimens regarding HPV-DNA presence or the detection of high-risk and low-risk types of HPV. Our data do not support the role of HPV infection in prostate carcinoma. Further studies are required to elucidate the role of HPV infection in human prostate carcinogenesis.

Detection of human papillomavirus DNA and p53 codon 72 polymorphism in prostate carcinomas of patients from Argentina

Background

Infections with high-risk human papillomaviruses (HPVs), causatively linked to cervical cancer, might also play a role in the development of prostate cancer. Furthermore, the polymorphism at codon 72 (encoding either arginine or proline) of the p53 tumor-suppressor gene is discussed as a possible determinant for cancer risk. The HPV E6 oncoprotein induces degradation of the p53 protein. The aim of this study was to analyse prostate carcinomas and hyperplasias of patients from Argentina for the presence of HPV DNA and the p53 codon 72 polymorphism genotype.

Methods

HPV DNA detection and typing were done by consensus L1 and type-specific PCR assays, respectively, and Southern blot hybridizations. Genotyping of p53 codon 72 polymorphism was performed both by allele specific primer PCRs and PCR-RFLP (Bsh1236I). Fischer's test with Woolf's approximation was used for statistical analysis.

Results

HPV DNA was detected in 17 out of 41 (41.5 %) carcinoma samples, whereas all 30 hyperplasia samples were HPV-negative. Differences in p53 codon 72 allelic frequencies were not observed, neither between carcinomas and hyperplasias nor between HPV-positive and HPV-negative carcinomas.

Conclusion

These results indicate that the p53 genotype is probably not a risk factor for prostate cancer, and that HPV infections could be associated with at least a subset of prostate carcinomas.

Epithelial abnormalities and precancerous lesions of anterior urethra in patients with penile carcinoma: a report of 89 cases

Urethral and penile tissues and their neoplasms are considered anatomically and pathogenetically different. Since we observed urethral dysplastic lesions and some similarities between noninvasive and invasive lesions of the anterior urethra and glans, we designed this study to document epithelial urethral abnormalities in patients with penile squamous cell carcinoma. We examined urethral epithelia from 170 penectomies with invasive squamous cell carcinoma finding a variety of primary epithelial abnormalities in 89 cases (52%) and secondary invasion of penile carcinoma to urethra in 42 cases (25%). Patients' average age was 68 years. Primary tumors measured 4 cm in average diameter and the majority were squamous cell carcinoma of the usual (67%) or verrucous type (15%). Primary epithelial abnormalities found were squamous intraepithelial lesions, metaplasias and microglandular hyperplasias. Urethral squamous intraepithelial lesions of high grade was found in six patients and of low grade in eight cases. Squamous metaplasia, seen in 69 cases, was the most frequent finding. Metaplasias were classified as nonkeratinizing and keratinizing. Nonkeratinizing metaplasias (57 cases) were variegated in morphology: simplex (26 cases), hyperplastic (12 cases), clear cell (11 cases) and spindle (8 cases). Keratinizing metaplasias (12 cases) showed hyperkeratosis and were more frequently associated with verrucous than nonverrucous penile squamous cell carcinoma. Microglandular hyperplasia was present in eight cases. Lichen sclerosus was associated with simplex squamous metaplasia in four cases. Despite the large size of the primary tumors, direct urethral invasion by penile carcinoma was present in only 25% of the cases. The presence of precancerous lesions in urethra of patients with penile carcinoma indicates urethral participation in the pathogenesis of penile cancer. Simplex squamous metaplasia is a common finding probably related to chronic inflammation. Keratinizing and hyperplastic squamous metaplasias may be important in the pathogenesis of special types of penile carcinomas such as verrucous carcinoma.

Presence of papillomavirus sequences in condylomatous lesions of the mamillae and in invasive carcinoma of the breast

BACKGROUND

Viruses including Epstein-Barr virus (EBV), a human equivalent of murine mammary tumour virus (MMTV) and human papillomavirus (HPV) have been implicated in the aetiology of human breast cancer. We report the presence of HPV DNA sequences in areolar tissue and tumour tissue samples from female patients with breast carcinoma. The presence of virus in the areolar-nipple complex suggests to us a potential pathogenic mechanism.

METHODS

Polymerase chain reaction (PCR) was undertaken to amplify HPV types in areolar and tumour tissue from breast cancer cases. In situ hybridisation supported the PCR findings and localised the virus in nipple, areolar and tumour tissue.

RESULTS

Papillomavirus DNA was present in 25 of 29 samples of breast carcinoma and in 20 of 29 samples from the corresponding mamilla. The most prevalent type in both carcinomas and nipples was HPV 11, followed by HPV 6. Other types detected were HPV 16, 23, 27 and 57 (nipples and carcinomas), HPV 20, 21, 32, 37, 38, 66 and GA3-1 (nipples only) and HPV 3, 15, 24, 87 and DL473 (carcinomas only). Multiple types were demonstrated in seven carcinomas and ten nipple samples.

CONCLUSIONS

The data demonstrate the occurrence of HPV in nipple and areolar tissues in patients with breast carcinoma. The authors postulate a retrograde ductular pattern of viral spread that may have pathogenic significance.

Transitional cell papilloma of the penis associated with human papilloma virus infection. Report of two cases

Condylomas are one of the most common human papilloma virus (HPV)-related benign lesions of the male genitourinary tract. Although rarely, HPV has also been detected along the urinary tract, using molecular techniques, in transitional cell neoplasms without microscopic signs of koilocytic atypia. When affecting the urethra, condylomas are usually limited to its third distal portion. However, transitional cell neoplasms of the urethra are exceptional and in most of the cases remain limited to its proximal portion. To the best of our knowledge, 12 cases of transitional cell carcinomas and only one case of typical transitional cell papilloma have been described in the anterior urethra. We report two exceptional cases of typical transitional cell papilloma of the glans of the penis near the fossa navicularis which showed microscopic signs of HPV infection.

Papillomavirus infections--a major cause of human cancers

The papillomavirus family represents a remarkably heterogeneous group of viruses. At present, 77 distinct genotypes have been identified in humans and partial sequences have been obtained from more than 30 putative novel genotypes. Geographic differences in base composition of individual genotypes are generally small and suggest a low mutation rate and thus an ancient origin of today's prototypes. The relatively small size of the genome permitted an analysis of individual gene functions and of interactions of viral proteins with host cell components. Proliferating cells contain the viral genome in a latent form, large scale viral DNA replication, as well as translation and functional activity of late viral proteins, and viral particle assembly are restricted to differentiating layers of skin and mucosa. In humans papillomavirus infections cause a variety of benign proliferations: warts, epithelial cysts, intraepithelial neoplasias, anogenital, oro-laryngeal and -pharyngeal papillomas, keratoacanthomas and other types of hyperkeratoses. Their involvement in the etiology of some major human cancers is of particular interest: specific types (HPV 16, 18 and several others) have been identified as causative agents of at least 90% of cancers of the cervix and are also linked to more than 50% of other anogenital cancers. These HPV types are considered as 'high risk' infections. Their E6/E7 oncoproteins stimulate cell proliferation by activating cyclins E and A, and interfere with the functions of the cellular proteins RB and p53. The latter interaction appears to be responsible for their mutagenic and aneuploidizing activity as an underlying principle for the progression of these HPV-containing lesions and the role of high risk HPV types as solitary carcinogens. In non-transformed human keratinocytes transcription and function of viral oncoproteins is controlled by intercellular and intracellular signalling cascades, their interruption emerges as a precondition for immortalization and malignant growth. Recently, novel and known HPV types have also been identified in a high percentage of non-melanoma skin cancers (basal and squamous cell carcinomas). Similar to observations in patients with a rare hereditary condition, epidermodysplasia verruciformis, characterized by an extensive verrucosis and development of skin cancer, basal and squamous cell carcinomas develop preferentially in light-exposed sites. This could suggest an interaction between a physical carcinogen (UV-part of the sunlight) and a 'low risk' (non-mutagenic) papillomavirus infection. Reports on the presence of HPV infections in cancers of the oral cavity, the larynx, and the esophagus further emphasize the importance of this virus group as proven and suspected human carcinogens.

Demonstration of URR-duplication variants of human papillomavirus type 6 in paraffin-embedded tissue sections of one condyloma acuminatum and one Buschke-Loewenstein tumour

Human papillomavirus type 6 (HPV 6) induces condylomata acuminata and laryngeal papillomas. Occasionally, HPV 6 may also be found in low-grade verrucous carcinomas. In some tumours, genetic analysis revealed the presence of HPV 6 variants with rearrangements, mostly DNA duplications, within the upstream regulatory region (URR). In this study, we analysed 98 formalin-fixed, paraffin-embedded condylomata acuminata obtained from 54 patients for the presence of URR-duplication variants of HPV 6. HPV 6 DNA could be amplified by polymerase chain reaction (PCR) from 40 samples. One condyloma acuminatum contained a HPV 6 genome with rearranged URR. Analysis using restriction enzyme cleavage suggested a DNA duplication within the URR of approximately 200 bp, spanning the Hpa II site at nt 7863 and the Dde I site at nt 7843 but not involving the Rsa I site at nt 7633. In addition, we analysed the distribution of the already characterized URR-duplication variant HPV 6AC1B within different paraffin-embedded tissue sections of a Buschke-Loewenstein tumour. No correlation could be demonstrated between the presence of the rearranged genome and malignant histological changes. This result and the demonstration of an URR-duplication variant in a typical condyloma acuminatum suggest that duplications within the URR of HPV 6 are not directly related to malignant progression of HPV 6-induced tumours.

Human papillomavirus type 16 associated with multifocal transitional cell carcinomas of the bladder in two transplanted patients

This report describes two cases of rapidly progressive, multifocal transitional cell carcinomas of the bladder that developed in two patients after renal and cardiac transplantation, respectively. In both cases human papillomavirus (HPV) type 16 DNA was detected using the polymerase chain reaction DNA amplification method. To our knowledge, this HPV type has not been previously described in multifocal bladder transitional cell carcinoma in transplanted patients. Our findings suggest that HPV may play a major role in the development of rapidly progressive, multifocal transitional cell carcinoma in immunosuppressed patients.

Presence and physical state of HPV DNA in prostate and urinary-tract tissues

Neoplastic and non-neoplastic tissues from the urinary tract and the prostate were analyzed for the presence of human papillomavirus (HPV) DNA. The analysis was performed by PCR using primers specific for HPV 6/11 and 16. HPV DNA was present in bladder, ureter, kidney and prostate, with percentages ranging between 46% and 87%. Benign and oncogenic HPV types were detected with similar frequencies both in non-neoplastic and in neoplastic biopsies, and HPV 16 was not preferentially associated with malignant lesions. In all instances, small amounts of HPV DNA were present in the tissues, suggesting the absence of productive infection. Analysis of the physical state of HPV DNA performed by 2-dimensional gel electrophoresis and Southern blot hybridization revealed that HPV 16 DNA harbored in the urinary tract can be integrated also in non-neoplastic tissues. The results indicate that HPV 16 does not seem to be associated with urinary-tract and prostate oncogenesis, but that these tissues may represent an important reservoir for the transmission of HPV types normally infecting the genital tract.

De novo carcinoma of the lower urinary tract in renal allograft recipients

Immunocompetence has been postulated as an important defense against the progression of urothelial carcinoma. Three cases of de novo lower urinary tract carcinoma in renal transplant recipients demonstrated the potential for unusually rapid urothelial extension and invasion in chronically immunosuppressed patients. Two patients had a history of perineal condyloma acuminata; tumors from 1 of these harbored the genetic sequences of human papillomavirus type 6. One patient had multiple manifestations of cyclophosphamide-related urothelial injury, including bladder carcinoma. Treatment of 2 patients culminated in a radical operation during which the remaining native urinary system was resected completely, with sacrifice of the allograft kidney in 1 and diversion into an ileal conduit in 1. The remaining patient underwent urethrectomy and partial cystectomy with a sigmoid conduit.

Interaction of human immunodeficiency and papilloma viruses: association with anal epithelial abnormality in homosexual men

During the 7th annual follow-up of our cohort of homosexual men in 1989, we tested the hypotheses that infection with human immunodeficiency virus (HIV) may enhance the expression of human papilloma virus (HPV) and that the development of anal epithelial abnormality is related to a biologic interaction between these two viruses. Overall, 41 (39%) of the 105 men had anal swabs positive for one or more genotypes of HPV 6/11, 16/18 or 31/33/35. Twenty-three (53%) of the 43 HIV-positive subjects harbored HPV compared to 18 (29%) of the 64 HIV-negative subjects (p = 0.012), including higher prevalence rates for HPV genotypes 16/18 (p = 0.01), 6/11 (p = 0.007), and 31/33/35 (p = 0.07). Multivariate logistic regression analysis of the HIV-positive subjects showed low CD4+ cell counts to be an independent risk factor for detection of HPV (p = 0.04) and in particular for HPV genotypes 31/33/35 (p = 0.02) and 6/11 (p = 0.07). In contrast, similar analysis of the HIV-negative subset showed that a positive antibody test for syphilis was associated with HPV (p = 0.03). Anal epithelial abnormalities were found in 13 (14%) of 92 technically adequate cytologic smears and were strongly associated with detection of any HPV genotypes by the dot-blot method (p = 0.01), and in particular with HPV genotypes 6/11 (p = 0.001). None of 15 subjects with HPV detected only by PCR had anal epithelial abnormality. We propose a viral interaction model, in which HIV-related immune deficiency allows reactivation of HPV, with a subsequent or concomitant appearance of epithelial abnormality.

Urethral involvement in female patients with bladder cancer. A study of 22 cystectomy specimens

The cystectomy specimens of 22 female patients with various types of bladder cancer were studied for evidence of urethral involvement. The bladder showed high-grade invasive transitional cell carcinoma in 18 patients, in 14 cases in association with flat carcinoma in situ (multifocal in 11 cases and unifocal in three). Three patients had multifocal carcinoma in situ of the bladder without evidence of invasion, and one patient had multifocal high-grade noninvasive papillary carcinoma. Urethral carcinoma in situ was observed in four of 14 patients (29%) with multifocal carcinoma in situ of the bladder, in three cases extending into the periurethral glands. This frequent concurrence of carcinoma in situ of the bladder with urethral and periurethral gland involvement, analogous to the carcinomatous involvement of the prostatic urethra and ducts in male patients, warrants caution in the intravesical therapy of female patients with superficial bladder cancer. The urethra showed invasive carcinoma in three of 18 patients (17%) with invasive bladder cancer (stromal invasion in two cases and vascular invasion in one). This finding reconfirms the use of routine urethrectomy in conjunction with cystectomy in female patients with invasive bladder cancer. An incidental finding was the presence of condylomatous changes in the urethra in five cases (23%).

Human papillomavirus type 6 in grade I transitional cell carcinoma of the urethra

Of 4 patients who underwent cystourethroscopy, biopsy and laser excision of suspected urethral condylomata acuminata 3 had coexistent grade I papillary transitional cell carcinoma of the urethra. Human papillomavirus type 6 messenger ribonucleic acid was demonstrated within biopsy specimens using tritium-labeled single-stranded antisense ribonucleic acid probes. Compared to condylomata the papillary transitional epithelium expressed less viral message, which might be expected in an epithelium that does not show full squamous epithelial or koilocytotic differentiation. Among these patients there was 1 papillary transitional lesion in the bladder that, although histologically similar, did not express human papillomavirus message, suggesting differential susceptibility of epithelium between the bladder and urethra. The finding of active human papillomavirus transcription within the urethral papillary transitional lesions raises the possibility of an active role for the virus in the pathogenesis of these lesions. These findings broaden the spectrum of epithelial types reported to support human papillomaviruses and provides impetus for a wider search for these viruses in other transitional cell neoplasms.

A comparison of methods for the detection of human papillomavirus DNA by in situ hybridization with biotinylated probes on human carcinoma cell lines. Application to wart sections

We compared nine different techniques for the detection of biotinylated DNA-DNA HPV hybrids on HeLa cells with 10-50 copies of HPV 18 DNA per cell. CaSki cells with 600 copies of HPV 16 DNA per cell and tissue sections from frozen or paraffin-embedded biopsy specimens. The cell samples were either cell deposits or cytocentrifuged or cultured slides. In most cases, the samples (cell deposits and tissue sections) were denatured with hybridization mixture prepared under stringent conditions (Tm = -17 degrees C) containing biotinylated DNA probes (cloned HPV types 1, 2, 6, 11, 16 and 18), at 90 degrees C for 10 min. In other cases (cytocentrifuged or cultured cells), the denaturation was performed by HCl hydrolysis and mild heating at 50 degrees C; the probes were denatured separately by heating. All the samples were further incubated overnight at 37 degrees C. For HPV DNA detection, three amplification levels were used on cell deposits. Only the techniques involving a three-step reaction (a rabbit anti-biotin antibody - a biotinylated goat anti-rabbit antibody - a complex of streptavidin-alkaline phosphatase or streptavidin-gold or streptavidin-fluorescein) gave satisfactory results, on both cell lines. With the one step reaction (an avidin-horseradish peroxidase, or streptavidin-alkaline phosphatase or streptavidin-fluorescein complex), no labeling of HeLa cells was observed with any of the HPV probes, including HPV 18. The techniques involving four steps (avidin or streptavidin - anti-avidin goat antibody or anti-streptavidin rabbit antibody - a biotinylated anti-goat (or anti-rabbit) antibody - a complex of avidin-biotin-peroxidase or streptavidin-biotin-alkaline phosphatase or streptavidin-biotin-horseradish peroxidase) resulted in high background on both cell lines. For the reproducible detection of low copy number of HPV DNA (less than 50 copies) such as occur in HeLa cells our data suggested that the three-step technique with the streptavidin-alkaline phosphatase complex was the method of choice. The most intense labeling was always obtained with cell deposits and the technique was successfully applied to frozen and paraffin-embedded tissue sections from typical warts.

Ameloblastoma in young persons: a clinicopathologic analysis and etiologic investigation

Ameloblastoma, an odontogenic tumor of ectodermal origin, has been reported to arise, on rare occasions, in a primordial or dentigerous cyst of a young person. Numerous authors have suggested differing nomenclatures for these ameloblastomas (e.g., mural, unicystic, monocystic, intracystic, cystogenic, cystic, plexiform unicystic) and have sought to describe and classify the clinical and histopathologic features. These tumors have been characterized as a distinct variant exhibiting less aggressive behavior and a lower rate of recurrence than conventional ameloblastoma. Furthermore, various etiologic factors have been proposed for these cystic ameloblastomas, including (1) nonspecific irritational factors such as extraction, caries, trauma, infection, inflammation, or tooth eruption; (2) nutritional deficit disorders, and (3) viral infection. The files of the combined accessioned cases of Emory University's and Temple University's oral pathology laboratories were searched and a review of the literature was performed. Thirty-eight cases of mandibular ameloblastoma (37 intraosseous, 1 peripheral) in persons 19-year-old and younger were found from a combined total of 311 accessioned cases of ameloblastoma (12.2%). The average age at diagnosis was 10.4 years for the 18 males and 20 females. Of the 33 cases in which race was stated, 19 (57.6%) were white and 14 (42.4%) were black. In the 28 cases in which a clinical diagnosis was offered, fifteen (53.6%) were thought to be dentigerous cysts. Ten cases from patients less than 19 years old were investigated by means of an immunohistochemical staining technique for the detection of human papilloma virus (HPV) genus-specific structural antigen in formalin-fixed, paraffin-embedded tissue. Three of the ten cases (cases 31, 37 and 38) were positive for HPV capsid antigen, whereas none of ten randomly selected ameloblastomas in adults was positive. A discussion of the clinical and histopathologic comparative findings, with emphasis on treatment results and possible HPV etiology, is included. The preliminary nature of finding HPV in the tumor cells is stressed, with recommendation for further verification and typing with the more sensitive in situ hybridization technique.