Odontogenic tumours and tumour-like lesions in Tanzania.

OBJECTIVES: To retrospectively document the pattern of occurrence of odontogenic tumours in Tanzania over fifteen years. DESIGN: The histologic types, site, age and sex distribution of odontogenic tumours in Tanzania from 1982 to 1997 were reviewed. Records of patients who presented to the four referral centres in Tanzania and who had histologically proven oral tumours and tumour-like conditions were examined. RESULTS: Odontogenic tumours comprised about 12.2% of all oral tumours and tumour-like conditions. The majority of odontogenic tumours (55.3%) were seen in patients below 30 years of age and they more commonly affected the mandible than maxilla. Ameloblastoma was the most commonly seen odontogenic tumour (73.7%), followed by odontogenic myxoma (10.3%). The site, sex, and histologic distribution of ameloblastoma did not differ from other African studies. Over 50% of patients with ameloblastoma presented to hospital late (after three or more years). CONCLUSION: In order to improve on the treatment outcome, the need for early detection and referral of patients by medical personnel and dentists is stressed.

Oral tumours in Tanzanian children based on biopsy materials examined over a 15-year period from 1982 to 1997.

AIM: To provide information on the types and distribution of oral tumours and tumour-like lesions occurring in a Tanzanian child population aged 0-16 years. DESIGN: Retrospective study of biopsy results from hospital records from 1982-1997. SETTING: Department of Histopathology, the Muhimbili Medical Centre (MMC) in Dar es Salaam. INTERVENTION/ METHODS: A total of 158 biopsy results, from 75 girls and 83 boys, were retrieved and studied. RESULTS: Malignant tumours were the most frequent (43.0%) followed by benign tumours (30.4%) and tumour-like lesions (26.6%). Burkitt's lymphoma was the most frequent malignant tumour accounting for 88.2% of all malignancies followed by squamous cell carcinoma (4.4%) and oral Kaposi's sarcoma (2.9%). Fibroma, papilloma and haemangioma were the most frequent benign tumours constituting 27.1%, 14.6% and 12.5%, respectively. Odontogenic cysts were the most frequent tumour-like lesions (28.6%) followed by fibrous dysplasia (19%) and giant cell granuloma (16.7%). CONCLUSION: The six most common oral lesions were Burkitt's lymphoma, fibroma, odontogenic cysts, fibrous dysplasia, papilloma and giant cell granuloma.

Frequent loss of p16 protein expression and high proliferative activity (Ki-67) in malignant melanoma from black Africans.

Malignant melanomas in black Africans are predominantly located on the lower extremities. Since their biological features have not been well focused, we studied 28 such cases with special reference to proliferative activity (Ki-67 expression), p16 and p53 staining, as well as microvessel density, all known to be involved in the progression of melanomas among whites. The findings were related to clinico-pathological characteristics. The tumours had a median thickness of 6.4 mm, ulceration was present in 71%, and vascular invasion in 36%, indicating the presence of advanced and aggressive melanomas. Further, loss of p16 protein expression was found in 50%, and high proliferative activity was present (median 41%). In contrast, strong p53 staining was rare (11%), although most tumours showed low-level positivity. Angiogenesis, as estimated by microvessel density, was significantly associated with vascular invasion (p = 0.022), supporting its role in the progression of these tumours. Thus, our findings indicate that melanomas located on the lower extremities in black Africans show several features of aggressiveness; in particular, the proliferative activity was high, and p16 alterations was frequent as evidenced by loss of protein staining. Our findings also indicated that the diagnosis is delayed among black Africans.

Correlation between argyrophilic nucleolar organizer region (AgNOR) counts and histologic grades with respect to biologic behavior of salivary adenoid cystic carcinoma.

The quantification of argyrophilic nucleolar organizer regions (AgNOR) was performed in 34 cases of adenoid cystic carcinoma (ACC) to determine (1) whether AgNOR count correlates with its different histologic grades pertinent to prognosis, and (2) whether AgNOR counts can offer any additional prognostic advantage over histologic grading. According to Szanto et al.'s histologic grading criteria (4), 12 cases were Grade 1, 7 cases Grade 2, and 15 were Grade 3. Patients were divided into 20 favorable cases (without metastases) and 14 unfavorable cases (with metastases). Although most Grade 3 tumors had high AgNOR counts (> or = 4) and Grade 1 tumors with low (< 4) AgNOR counts outnumbered those with high AgNOR counts, considerable overlap of AgNOR values in different grades was observed. However, all unfavorable cases had high AgNOR counts regardless of their histologic grades, suggesting that the metabolic alterations associated with the malignancy level of ACC may partly be portrayed by the AgNOR count, irrespective of the histologic appearance. Cumulative survival rates of Grade 1 tumors and of tumors with low AgNOR counts were better than those of Grade 3 tumors and those with high AgNOR counts. Within the limited number of cases in this series the AgNOR count exhibits a potential for identifying some aggressive ACCs that cannot be detected by histology alone.

Prognostic value of argyrophilic nucleolar organizer regions (AgNOR) count in adenoid cystic carcinoma of salivary glands.

A retrospective study was performed on 34 patients with adenoid cystic carcinoma (ACC) to see if quantification of argyrophilic nucleolar organizer regions (AgNOR) was correlated with their prognosis. Mean follow-up period was 113 months. According to detailed clinical data that included tumor recurrences, metastases and patient survival conditions, two groups were classified. Group 1 consisted of 20 live patients without metastases, of whom 16 were free of disease, while group 2 comprised 14 patients with metastases among whom 12 died of tumor. The silver staining technique was applied to paraffin embedded specimens. In each case, 300 nuclei were randomly examined and the mean AgNOR per nucleus was calculated. All patients from group 2 had mean AgNOR counts greater than 4, whereas 65% of patients from group 1 had mean AgNOR counts less than 4. In addition, statistical analysis showed that the pooled mean AgNOR count in group 2 was significantly higher than in group 1 (P < 0.01). The present results suggest that silver staining technique promises to be a useful supplementary method for prognostic evaluation of salivary ACC, and may be performed before planning the treatment.

Proliferative activity of salivary gland pleomorphic adenomas and myoepitheliomas as evaluated by the proliferating cell nuclear antigen (PCNA) labeling index (LI).

Thirteen examples of pleomorphic adenoma (PA) and 4 of myoepithelioma (Me, 2 plasmacytoid cell type, 2 mixed cell type) were examined with respect to their proliferative activity on the basis of proliferating cell nuclear antigen (PCNA) immunohistochemistry. In PA, PCNA labeling index (LI) in tubular/trabecular/solid areas was significantly higher than that in myxomatous or chondroid areas. Although the mean value of LI in PA and Me was not statistically different (PA; 3.02 +/- 1.03%, Me; 3.19 +/- 1.76%), the Me of mixed cell type composed of epithelial, spindle or clear neoplastic myoepithelial cells had significantly higher LI, indicating the possibility of more rapid growth than PA. The small difference in the mean value of PCNA LI between PA and the mixed cell type of Me, however, suggests that enucleation with a margin of normal uninvolved tissue remains the recommended treatment for Me, as well as for PA.

Jaw cysts with orthokeratinization: analysis of 12 cases.

The clinico-pathologic, immunohistochemical and radiological features of 12 jaw cysts with a prominent orthokeratinized epithelial lining were studied and compared with those of typical odontogenic keratocysts and dentigerous cysts. They differed significantly from odontogenic keratocysts in terms of biologic behavior and histopathologic findings. Although immunohistochemical staining of the epithelial linings for cytokeratins, EMA, CEA and involucrin has not shed any light on the histogenesis of these lesions, staining patterns for these markers were significantly different from those of odontogenic keratocysts and non-keratinized dentigerous cysts. Radiologically, nine cases appeared as dentigerous cysts; two cases, one with sebaceous differentiation, as non-dentigerous unilocular cysts, and the remaining one was exceptional as it showed multiple epidermal cysts with prominent dermal appendages histologically. It is suggested that most of the orthokeratinized jaw cysts may belong to clinico-pathological entities different from odontogenic keratocysts with the majority representing dentigerous cysts with orthokeratinization. The possibility of the existence of rare central dermoid or epidermoid cysts is also to be considered.

Clear cell tumors of minor salivary gland origin. An immunohistochemical and ultrastructural analysis.

Three cases of monophasic glycogen-rich clear cell tumors of palatal gland origin were examined immunohistochemically and ultrastructurally in attempts to characterize their cellular composition. Despite their histologic resemblances, the clear cells from each case showed different immunohistochemical features. In case 1 the extensive positivity for vimentin and S-100 protein, in addition to the focal expression of actin and glial fibrillary acidic protein, strongly suggested that the clear cells were myoepithelial in nature. In contrast, the clear cells from case 2 exhibited both keratin and epithelial membrane antigen positivity, as well as ultrastructural features that suggested that they were glandular epithelial in nature. In case 3 no special markers except for keratin could be detected, indicating the less differentiated nature of the clear cells. These results show the heterogeneity of the clear cell tumor group of minor salivary glands.