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The underlying molecular abnormalities associated with head and neck squamous cell carcinoma in young adults (< 40 years) are unknown. We analyzed DNA extracted from paired microdissected samples of normal squamous epithelia and invasive oral squamous cell carcinomas from 36 young adults at microsatellite loci commonly found in older patients and correlated the results with clinicopathologic parameters and outcome. Our results showed that 30 of the 36 (83%) tumors manifest loss of heterozygosity (LOH) in at least one marker. Microsatellite instability was manifested in only six tumors (< 17%). The highest incidences of alterations were noted at markers D9S168 (9p23-22), TP53 (17p13), and D17S799 (17p11) on the short arms of chromosomes 9 and 17. In general, the incidences of LOH at 3, 9 and 17p regions in young adults were similar to those found in older patients. No correlation between LOH at chromosomes 3, 9, and 17p and clinicopathologic parameters was found. Our study indicates that chromosomal regions with frequent genetic alterations involved in young adult squamous tumorigenesis are similar to those reported in older patients. Further studies of other chromosomes in this population are underway to define the novel molecular features of these tumors.

Previous studies indicated that Taiwan betel quid is a promoter rather than an initiator during the carcinogenesis of hamster buccal pouch carcinoma. The maximum promoting activity can be demonstrated 24 weeks after betel quid implantation, following an initial application of 0.5% DMBA (7,12-dimethyl benzanthracene) three times per week for 4 weeks. In the present study, components of Taiwan betel quid and its additives (dry betel nut fibre, piper betel, slaked lime, cold aqueous extract, and hot aqueous extract) were applied respectively or in various combinations to investigate their promoting activity. One hundred and thirty Syrian hamsters were divided into 13 groups based on different combinations of the betel quid ingredients applied. The incidence of tumours in the hamster buccal pouch was significantly higher in groups exposed to dry betel nut fibre (P < 0.01) and cold aqueous extract (P < 0.05). The results indicate that betel nut fibre and cold aqueous extract are the major components of betel quid that may promote carcinogenesis in the hamster buccal pouch.

DNA sequences closely related to herpesvirus-like sequences have been found in AIDS-associated Kaposi's sarcoma. Subsequent studies indicate that these DNA sequences may be consistently found in AIDS Kaposi's sarcoma and non-AIDS Kaposi's sarcoma from different geographic regions. Oral Kaposi's sarcoma is rare and the specificity of this viral DNA in oral Kaposi's sarcoma and in other oral neoplasms has not been examined. A total of 77 oral neoplasms, including 3 Kaposi's sarcoma specimens from 2 patients with AIDS, were analyzed by polymerase chain reaction for the presence of this herpesvirus-like DNA sequence with the 330-233 primers. All three specimens of oral AIDS-Kaposi's sarcoma from two patients were positive for this DNA sequence. All of the other intraoral lesions including hemangioma, pyogenic granuloma, and various types of epithelial neoplasms, however, had negative reactions. Our results further confirm that oral Kaposi's sarcoma appears to be associated with this herpesvirus-like DNA sequence.

Sixty squamous cell carcinomas of tongue and buccal mucosa were examined for expression of p53 protein by using an immunohistochemical technique improved by an antigen retrieval method. Twenty-seven (45%) tumors demonstrated strongly positive staining. Thirteen of p53-positive tumors (48%) also exhibited overexpression of p53 in immediately adjoining hyperplastic or pre-malignant epithelium. All 22 metastatic lymph nodes and 18 local recurrent lesions (except two) had an identical p53 immunophenotype to their corresponding primary sites. Mitotic indices were significantly higher in p53-positive tumors (P < 0.01); however, no association of PCNA scores with p53 expression was found (P > 0.1). There was no correlation between p53 overexpression and tumor grade, size and staging, vascular invasion, lymph node metastasis, and early local recurrence. Overexpression of p53 was found to be relatively higher, although not statistically significant, in nonsmokers than in heavy smokers (66.7% vs. 42.9%), and in nonbetel-quid chewers than in heavy chewers (62.5% vs. 34.2%). These data are consistent with the hypothesis that inactivation of p53 protein may occur in the early phases of oral tumorigenesis. It may not be a useful prognostic marker but could possibly be used for risk assessment and surveillance of local recurrence.

Proliferating cell nuclear antigen (PCNA) is a nuclear protein synthesized in the late G1 and S phase of the cell cycle which can be detected immunohistochemically in paraffin-embedded tissue as a useful marker for the proliferating fraction of cells in tissue specimens. Thirty-eight cases of oral squamous cell carcinoma were studied in groups according to clinical staging and histological grading (UICC system), these included 5 cases of T1, 13 cases of T2, and 20 cases of T3, and 19 cases of G1, 12 cases of G2, and 7 cases of G3. The mean percentage of PCNA positively stained tumor cells in this series was 29.2. The mean percentages of PCNA-positive cells in each stage and grade were: T1 (13.7%), T2 (24.4%), and T3 (34.3%); G1 (30.5%), G2 (24.8%), and G3 (33.2%). The results indicate that the percentage of PCNA positively stained tumor cells in oral squamous cell carcinoma was significantly greater when tumor size was larger than 2 cm (T1 versus T2/T3). However, there was no significant difference between T2 and T3. There was no correlation between the number of PCNA-stained tumor cells and histological grade.

The distribution pattern of certain monosaccharides in the epithelial cells of the hamster buccal pouch was studied during carcinoma development induced by 9,10-dimethyl-1,2-benzathrancene (DMBA). An avidin-biotin-peroxidase complex (ABC) immunohistochemical technique with high affinity biotinylated lectins was employed to identify monosaccharides. Lectins used in this experiment included Concanavalin A (Con A), for identifying mannose or glucose, Ricinus communis agglutinin I(RCA-I), for identifying galactose, and Ulex europaeus agglutinin I(UEA-I), for identifying fucose. The results show that in normal buccal pouch epithelial cells, fuctose or galactose were concentrated predominantly on the cellular membrane, while mannose and glucose were distributed in the cytoplasm. In the epithelial cells undergoing neoplastic transformation induced by DMBA, most cells showed decreased staining of the above-mentioned monosaccharides, while in other areas the cells were heavily stained. However, the most striking change which occurred was that galactose and fucose shifted from the cellular membrane to the intracytoplasmic area during the malignant transformation. Thus, the changes of anatomic location and intensity of staining of monosaccharides in the buccal pouch epithelium may be used as a criteria for early histochemical diagnosis of malignant transformation.

The papillary lesions of oral verruca vulgaris, condyloma acuminatum, and verrucous carcinoma were examined for the presence of papovavirus antigens by the peroxidase-antiperoxidase immunohistochemical methods. The antigens could be detected in the nuclei of cells only in the stratum granulosum and stratum corneum in some cases of verruca vulgaris and condyloma acuminatum but in no case of verrucous carcinoma.