Anal carcinoma: a clinical approach to p53 and RB gene proteins

The role of p53, retinoblastoma (RB) and c-erbB-2 gene proteins in the pathogenesis of anal carcinomas has been examined. A total of 97 patients were included in the study. c-erbB-2, RB and p53 proteins were abnormal in 0, 5 and 34% of the cases, respectively. No correlation was observed between p53 and age, sex, tumour stage, histopathological tumour grading, human papilloma virus (HPV) affection or prognosis. It is concluded that the c-erbB-2 gene is not involved in the development of anal carcinomas; the role of the RB gene is somewhat uncertain, while p53 may be involved in about 1/3 of the cases. However, p53 is not correlated with HPV infection or clinical or histopathological data.

Evaluation of the prognostic significance of cathepsin D, epidermal growth factor receptor, and c-erbB-2 in early cervical squamous cell carcinoma. An immunohistochemical study

BACKGROUND

This study evaluated the prognostic significance of immunohistochemical staining for cathepsin D, epidermal growth factor receptor (EGFR), and c-erbB-2 in patients with early cervical squamous cell carcinoma.

METHODS

This retrospective analysis comprised 132 patients, all subjected to radical hysterectomy with bilateral pelvic lymphadenectomy for International Federation of Gynecology and Obstetrics (FIGO) Stage IB cervical squamous cell carcinoma. Immunohistochemical staining was correlated with various histopathologic and morphologic characteristics (i.e., tumor size, grade of differentiation, vessel invasion, invasion into parametria, and lymph node metastasis) and relapse free survival.

RESULTS

Positive staining for cathepsin D was observed in 47% of tumors, more frequent in tumors giving rise to lymph node metastases. The relapse free survival was lower for patients with cathepsin D positive tumors. Overexpression of EGFR was observed in 25.8% of the tumors. There was no correlation with any of the histopathologic variables investigated. Relapse free survival was lower for patients with tumors overexpressing EGFR. Immunohistochemical staining for c-erbB-2 was observed in 12.1% of tumors with no correlation with relapse free survival. In multivariate analysis, immunostaining of cathepsin D and EGFR obtained independent prognostic significance, and considered together (both negative, one positive, or both positive) was the strongest prognostic factor after tumor size.

CONCLUSIONS

Immunohistochemical staining for cathepsin D and EGFR is useful as a tool for evaluation of tumor aggressiveness in patients with early cervical squamous cell carcinoma.

Evaluation of the prognostic significance of nm23/NDP kinase protein expression in cervical carcinoma: an immunohistochemical study

The objective of this study was to evaluate the prognostic significance of immunohistochemical staining for nm23/nucleoside diphosphate (NDP) kinase in cervical carcinoma. A retrospective analysis of 176 patients with cervical carcinoma FIGO stage IB treated with radical hysterectomy and pelvic lymphadenectomy from 1987 to 1990 was conducted. Immunohistochemical staining using the polyclonal nm23-H1/NDP kinase A antibody was correlated to various histopathological and morphological characteristics (tumor size, histologic type, grade of differentiation, vessel invasion, invasion into parametria, and lymph node metastasis) and relapse-free survival. For controls, sections were obtained from 10 hysterectomy specimens with normal cervical epithelium. Staining for nm23/NDP kinase was observed in 90% of control cases and in 70.5% of cases of cervical carcinoma, more frequent in squamous and adenosquamous cell carcinoma than in adenocarcinoma and more frequent in poorly differentiated than in more highly differentiated tumors. There were no differences related to size of tumor or invasion into vessels or parametria or occurrence of lymph node metastasis. The relapse-free survival was lower for patients with squamous cell and adenosquamous tumors with positive immunostaining for nm23/NDP kinase than for those with negative tumors when evaluated in univariate analysis. In multivariate analysis with tumor size, vessel invasion, invasion into parametria, grade of differentiation, and lymph node metastasis included, this difference was no longer significant. In patients with adenocarcinoma no difference was found. In conclusion, we did not find immunostaining for nm23/NDP kinase to be a useful indicator for prognosis in cancer of the uterine cervix.

TP53 alterations in atypical ductal hyperplasia and ductal carcinoma in situ of the breast

Abnormalities in the TP53 tumour suppressor gene in 75 atypical ductal hyperplasias and 62 ductalcarcinomas in situ (DCIS) of the breast were studied using immunohistochemistry and mutation analysis. Accumulation of p53 protein was detected in 10 out of 62 (16%) DCIS, whereas no cases of positive staining was observed in the atypical lesions. TP53 mutations were identified in four out of 30 (13%) DCIS by constant denaturant gel electrophoresis (CDGE). Two of these cases were positive and two negative for p53 protein. A total of 12 out of 62 DCIS (19%) carried TP53 mutation and/or p53 protein over-expression. The present results suggest that TP53 alterations may be important in the development of a subset of DCIS.

Evaluation of the prognostic significance of nm23/NDP kinase and cathepsin D in anal carcinomas. An immunohistochemical study

Reduced expression of nm23/NDP kinase and increased expression of cathepsin D seem to be correlated with a high metastatic potential for a variety of malignancies. Nm23/NDP kinase and cathepsin D have been correlated with several clinical variables, including survival in 96 patients with squamous cell carcinoma of the anal canal. Immunohistochemical methods were used on paraffin-embedded biopsies. Seventy-six (79%) anal carcinomas were nm23/NDP kinase positive, whereas 35 (36%) and 28 (29%) of the cases were cathepsin D positive in tumor cells and stromal cells, respectively. We have found no indication that the extent of cathepsin D staining has any prognostic significance. The overall survival of patients with tumours positive for nm23/NDP kinase in the cytoplasm was significantly shorter than that of patients with anal carcinomas negative for nm23/NDP kinase.

Involvement of the pRb/p16/cdk4/cyclin D1 pathway in the tumorigenesis of sporadic malignant melanomas

Biopsies from 61 sporadic metastatic malignant melanomas and five melanoma cell lines were examined for homozygous deletions and mutations in the CDKN2 gene (p16). As the p16 protein is involved in a cell cycle regulatory pathway consisting of at least pRb, cdk4 and cyclin D1, the tumours were also screened for amplifications of the last two genes. Moreover, the transcript levels of the genes were determined and the results compared with the immunohistochemically assessed expression of pRb. Altogether, homozygous deletions of CDKN2 were found in seven tumours (11%) and two of five cell lines, whereas a mutation was detected in only one biopsy, indicating that in sporadic melanomas the former mechanism is predominant for inactivating this gene. Notably, in total 59% of the metastatic lesions lacked detectable expression of p16 mRNA, whereas all the biopsies were found to express pRb. In accordance with the postulated negative feedback loop between p16 and pRb, one melanoma cell line showed overexpression of CDKN2 mRNA together with very low levels of the Rb protein. Amplification of the other two genes may not be important in the tumorigenesis of melanomas, as only one CDK4 and no CCND1 amplification was observed. However, highly elevated CDK4 mRNA levels, compared with that seen in a panel of normal tissues, were observed in 76% of the tumours, accompanied in 71% of the cases by high expression of the CCND1 cyclin activator. Although a low frequency of CDKN2 DNA aberrations was observed, the high number of tumours that lacked CDKN2 expression but showed overexpression of CDK4 and/or CCND1, suggest that functional inactivation of pRb through this pathway may be involved in the development or progression of sporadic human melanomas.

Expression of retinoblastoma tumor suppressor gene protein, epidermal growth factor receptor, and c-erbB-2 oncoprotein in primary vaginal carcinomas

Forty-six primary vaginal carcinomas were examined immunohistochemically for expression of retinoblastoma (RB) protein, epidermal growth factor receptor (EGFR), and c-erbB-2 oncoprotein. The results demonstrated that RB protein was not lost in any of the cases, suggesting that structural abnormalities of the RB gene may not play an important role in the pathogenesis of vaginal carcinoma. Fifteen and 11% of the cases showed increased expression of EGFR and c-erbB-2 oncoprotein, respectively, indicating that these oncoproteins may be involved in the neoplastic process of a minority of vaginal carcinomas. Overexpression of EGFR and c-erbB-2 oncoprotein had no prognostic significance in vaginal carcinomas.

Lack of expression of c-erbB-2 oncoprotein in human esophageal squamous cell carcinomas

Fifty-one cases of esophageal squamous cell carcinoma were immunohistochemically investigated with monoclonal c-erbB 2 oncoprotein antibody. No tumor showed plasma membrane immunostaining for c-erbB-2 protein. Occasionally, unspecific cytoplasmic staining was found in minor tumor cell populations. The present results show that c-erbB-2 oncoprotein is not overexpressed in esophageal squamous cell carcinomas and does not play a central role in the tumorigenesis.

Immunohistochemical detection of nm23/NDP kinase and cathepsin D in medullary carcinomas of the thyroid gland

Reduced expression of nm23/NDP kinase and increased expression of cathepsin D seem to be correlated with the high metastatic potential in a variety of malignancies. The expression of nm23/NDP kinase and that of cathepsin D have been evaluated by means of an immunohistochemical technique in paraffin-embedded tissues from 44 primary medullary carcinomas of the thyroid gland (MCT) and from the corresponding lymph node metastases in 32 of these cases. In addition, lymph node metastases from 4 cases were studied. We found that 36 of 44 (82%) primary and 26 of 36 (72%) lymph node metastatic MCT were nm23/NDP kinase positive, whereas 14 of the 44 (32%) primary and 17 of the 36 (47%) lymph node metastatic MCT were cathepsin D positive. We found no indication that the nm23/NDP kinase level has any prognostic significance in MCT. The cathepsin D level is close to being prognostically significant in this study, and we cannot exclude the possibility that it could be of prognostic value. However, it seems to be quite weak, and therefore of little use in a clinical situation.

High incidence of human papillomavirus in 146 cervical carcinomas. A study using three different pairs of consensus primers, and detecting viral genomes with putative deletions

Polymerase chain reaction (PCR) primer sets and probe-cocktails were used for human papillomavirus (HPV) detection and typing of 146 fresh frozen biopsies of cervical carcinoma. We obtained a high detection rate (96%) by using three sets of consensus primer pairs directed at the L1 and E1 regions of HPV and by probing with a cocktail of random-labelled consensus and type-specific PCR products derived from HPV plasmids. In addition, we performed type-specific PCR amplification with E6-E7 primers. The procedure was designed to detect all HPV-positive cases in a rapid, sensitive and specific way. In addition, by using different regions for amplification, we detected cases with putative genomic deletions in HPV. All the negative PCR and DNA isolation controls were negative. The six negative samples were negative with all probe-cocktails and type-specific primers and three of these negative samples were clear cell carcinomas. The detection rate was similar in squamous carcinomas and in adenocarcinomas and type 16 was most common (65%) in both types of carcinoma. There were no double infections of human papillomavirus 16 and 18.

TP53 gene mutations and protein accumulation in primary vaginal carcinomas

Primary carcinomas from 46 patients were screened for TP53 alterations. Immunohistochemistry demonstrated nuclear TP53 protein accumulation in 22 (48%) cases using the polyclonal CM1 antiserum, whereas 15 (33%) cases showed positive nuclear staining with the mononuclear antibody PAb 1801. Constant denaturant gel electrophoresis (CDGE) was used to screen 27 of the vaginal carcinomas for mutations in the conserved regions of the TP53 gene (exons 5-8). Six of these tumours (22%) contained mutations: four were found in exon 5 and two in exon 8. A total of 50% of the primary vaginal carcinomas carried a TP53 alteration. These results indicate that TP53 abnormalities may be involved in the development of these tumours. However, there was no significant association between TP53 abnormalities and survival.

Accumulation of p53 protein in human malignant melanoma. Relationship to clinical outcome

Paraffin-embedded tissue from the primary tumours of 116 patients with malignant melanoma, and in 40 cases also from corresponding metastases, were examined for accumulation of p53 protein. The fraction of tumours with positive p53 immunostaining was 13% in the least invasive and 36% in the most invasive primary lesions and 48% in the metastases. Where comparisons could be made, both the level and pattern of p53 immunoreactivity were the same in the primary and metastatic tumours. Nine (50%) patients with p53-positive and 34 (39%) with p53-negative primaries relapsed during the first 5 years, but no difference in disease-free period was observed between the two groups. However, an overall longer survival time was observed among patients with p53-positive primaries, especially for those with tumours less invasive than 3.0 mm. Notably, all 11 patients in this group were alive 5 years after diagnosis of the disease, whereas 15 out of 70 (21%) patients with p53-negative tumours died in same period. The results show that an increased level of p53 protein does not indicate increased degree of malignancy in melanoma, but rather suggests a more favourable disease progression.

Null cell adenomas and oncocytomas of the pituitary gland

This review highlights the most interesting features of null cell adenomas and oncocytomas of the pituitary gland. Recently, application of sensitive methods have documented a very low amount of active hormone production in these clinically nonfunctioning tumours. However, further studies are needed to clarify the histogenesis of null cell adenomas and oncocytomas.

Proliferative activity of synovial sarcoma: an immunohistochemical evaluation of Ki-67 labeling indices of 52 primary and recurrent tumors

The relationship between cell differentiation and proliferation in biphasic synovial sarcoma (BSS) and the connection between the two components of these tumors and monophasic synovial sarcoma (MSS) are still unknown. In this study we specifically compared the Ki-67 labeling indices (Ki-67-LI) in the solid/glandular and spindle cell components of primary BSS (n = 8) as well as the values thus obtained in primary BSS both outside clear-cut biphasic areas (n = 7) and in primary MSS (n = 23). We also compare the Ki-67-LI of primary tumors (seven BSS, seven MSS) and their respective first recurrences. We observed that the cells of the solid/glandular component of BSS proliferate significantly faster (p = 0.007) than those of spindle cell areas. No significantly different Ki-67-LI were observed in the comparison of the solid/glandular areas of BSS with the spindle/epithelioid component of BSS without clear-cut biphasia and MSS. No significant differences of Ki-67-LI were observed in the comparison of primary tumors of both subtypes with their respective first recurrences. The implications of the low proliferative activity of the spindle cell component of BSS exhibiting clear-cut biphasia, which was also confirmed in a concurrent study using anti-proliferating cell nuclear antigen/Cyclin PC10, remains to be clarified.

[Microwave oven in immunohistochemistry. An important tool for determination of antigens in formalin-fixed and paraffin-embedded tissue]

Immunocytochemical methods are important tools for identifying antigens in tissue sections and cell smears. Some antigens were retrieved in formalin-fixed and paraffin-embedded tissues by means of a microwave technique. This method also increased the sensitivity of the immunohistochemical detection of several other antigens. Altogether, microwave boiling of the tissue sections in citrate buffer clearly improved the immunoreactivity for cytokeratin 18, oestrogen receptor, Ki-67 protein, PCNA, p53 protein, retinoblastoma gene protein and c-erbB-2 protein. This new technique, which can be applied in every pathology laboratory, will facilitate the application of immunohistochemical methods for research and diagnostic work.

Prevalence and physical state of human papillomavirus DNA in anal carcinomas

Epidemiologic studies suggest that human papillomavirus (HPV) plays an important role in the development of squamous cell carcinoma of the anal canal. However, in previous studies the prevalence of HPV found in tumor varied from 0 to 85%. This study was performed to investigate the prevalence and physical state of HPV DNA in anal carcinomas. HPV infection was examined using in situ hybridization and polymerase chain reaction. HPV DNA was detected in 80/99 (81%) of the tumors, including 66/74 (89%) from females and 14/25 (56%) from males. HPV16 was demonstrated in 84% of the females and 52% of the males. HPV18, HPV31, and HPV33 could be demonstrated in 5% or less of the cases. In situ hybridization technique showed that 100% of the virus-infected cases had punctate signal and 67% had in addition a diffuse signal, indicating integrated and episomal virus DNA, respectively. The integrated and episomal HPV DNA coexisted in the majority of the tumor cell nuclei. This study indicates that infection and integration of HPV DNA may play an important role in the pathogenesis of anal canal carcinomas.

The expression of c-erbB-2 (HER-2/neu) oncogene in invasive ovarian malignancies

The expression of c-erbB-2 oncogene has been studied in 74 formalin fixed paraffin embedded invasive epithelial ovarian malignancies using a monoclonal c-erbB-2 protein antibody. Only four (5.4%) tumors showed membrane immunostaining. FIGO stage, size of residual disease after primary surgery, histologic type and tumor grade, were identified by the log rank test as prognostic factors for survival. No difference in survival was observed between those with and without membrane staining (24 months probability of survival: 50% and 55.4% respectively). Our results did not show any adverse prognostic effect of c-erbB-2 protein expression in our patients.

Expression of laminin, collagen IV, fibronectin, and type IV collagenase in gastric carcinoma. An immunohistochemical study of 87 patients

BACKGROUND

This study attempted to determine if there is a pattern of matrix/matrix-degrading-enzyme immunoreactivity related to the morphologic types of gastric carcinoma or to their invasiveness.

METHODS

The authors performed an immunohistochemical study of the basement membrane antigens laminin and collagen IV, fibronectin, and Type IV collagenase in a series of 87 gastric carcinomas and their respective nodal metastases (n = 329).

RESULTS

Laminin expression was observed almost exclusively in carcinomas of the intestinal type. The expression of collagen IV was significantly higher in intestinal (52%) and atypical (44%) carcinomas than in diffuse (10%) carcinomas; collagen IV expression also was significantly correlated with lymphatic invasion and aneuploidy. Ninety percent of the carcinomas expressed fibronectin, mostly in the connective tissue at the invading edge of the tumors; fibronectin expression was significantly related to the expanding growth pattern of the neoplasms. Eighty-six percent of the tumors expressed Type IV collagenase, regardless of the histologic type or invasive properties. No relationship was observed between the expression of any of the antigens and the S-phase fraction of the tumors. No significant differences were found between the immunohistochemical profile of the primary tumors and their metastases.

CONCLUSIONS

The authors conclude that the expression of basement membrane antigens is related to the type of gastric carcinomas, rather than the cell differentiation or proliferative activity of the tumors. The putative prognostic meaning of the relationship between collagen IV immunoreactivity and aneuploidy and lymphatic invasiveness of the carcinomas remains to be clarified.

Coexistence of episomal and integrated HPV16 DNA in squamous cell carcinoma of the cervix

AIMS

To investigate the integration of human papillomavirus (HPV)16 in 13 HPV16 positive cervical squamous carcinomas.

METHODS

Samples were investigated by Southern blot analysis of the Pst I digestion pattern, two-dimensional gel-electrophoresis, and in situ hybridisation.

RESULTS

Integration of HPV16 was found in all cases. In 12 biopsy specimens episomal HPV16 DNA and integrated HPV16 DNA were seen. The episomal DNA occurred as dimers and multimers. In situ hybridisation showed that both integrated and episomal HPV16 DNA were present in the same cell in most tumour cell nuclei.

CONCLUSIONS

An intact episomal E2 gene is present in most cases of these cervical cancers, and could therefore replace the regulatory function of an integrated defective E2 gene.

Retinoblastoma and p53 tumour suppressor gene protein expression in carcinomas of the thyroid gland

One hundred and thirty-one thyroid tumours were examined immunohistochemically for expression of retinoblastoma (RB) and p53 protein. The results demonstrate that RB protein is not lost in any cases, indicating that inactivation of the RB gene is unlikely to play a central role in the pathogenesis of thyroid tumours. Eighteen of 24 (75 per cent) undifferentiated carcinomas, 6 of 32 (19 per cent) papillary carcinomas, 5 of 29 (17 per cent) follicular carcinomas, and 6 of 46 (13 per cent) medullary carcinomas showed p53 protein nuclear staining. In 46 per cent of the undifferentiated carcinomas many of the tumour cells had accumulated p53 protein, whereas in the other positive cases less than 5 per cent of the cells had increased p53 protein levels. Our results strongly suggest that p53 protein abnormalities play a crucial role in the progression of well-differentiated to undifferentiated thyroid carcinomas.

Immunohistochemical profile of synovial sarcoma with emphasis on the epithelial-type differentiation. A study of 49 primary tumours, recurrences and metastases

The relationship between biphasic (BSS) and monophasic (MSS) subtypes of synovial sarcoma (SS) as well as the relationship between cells of solid/glandular areas and the spindle cells of BSS remain controversial. In order to further evaluate the immunohistochemical phenotype of SS we studied 34 primary tumours (15 BSS; 19 MSS), 7 recurrences (4 from primary BSS; 3 from primary MSS) and 8 metastases (7 BSS; one MSS), using several antibodies (EMA, CEA, keratins 1, 4, 5/6, 7, 8, 13, 18, 19, 20, vimentin, collagen IV and laminin) that work in paraffin-embedded material. Spindle cells outside solid/glandular areas of BSS and in MSS showed immunoreactivity for keratins 5/6, 7, 8, 18 and 19. The transition of solid/glandular areas to surrounding spindle cells also showed keratin staining and failed to show a distinct separation regarding the immunoreactivity for laminin and collagen IV. Peripheral cells of solid/glandular areas were immunoreactive for vimentin. No major differences were observed between immunophenotypical cell profiles of BSS and MSS, apart from the exclusive immunostaining of solid/glandular areas of BSS for keratin 13 and CEA. Downgrading of keratin and extracellular matrix antigens immunoreactivity was observed when primary tumours were compared to recurrent and/or metastatic tumours of both subtypes (MSS and BSS). We conclude that SS should be regarded as carcinomas of soft tissues with an immunohistochemical phenotype depending on the degree of epithelial differentiation: spindle cells (MSS and BSS) predominantly expressing simple keratins, and poorly differentiated (solid/glandular) as well as well-differentiated (glandular) areas (BSS) expressing, in addition, complex epithelial-type keratins.

Small cell carcinoma of the cervix. A clinicopathologic study of 26 patients

BACKGROUND

Small cell carcinoma of the cervix is a rare and aggressive tumor. Most gynecologic oncology centers have little experience with this tumor, and only small series have been published.

METHODS

Twenty-six patients with small cell carcinoma of the uterine cervix were treated at the Norwegian Radium Hospital. Clinical data, immunohistochemical characteristics, and infection with human papillomavirus were studied.

RESULTS

Twelve tumors were of oat cell type and 14 of intermediate cell type. Twelve tumors were associated with other forms of carcinoma: squamous cell carcinoma (6 tumors), adenocarcinoma (5 tumors), and adenocarcinoma in situ (1 tumor). Neuroendocrine differentiation was expressed in 79% of the tumors. Human papillomavirus (HPV)-18 was detected in 40% of the tumors and HPV-16 in 28%. Fifteen patients had Stage I disease, 7 had Stage II, 2 had Stage III, and 3 had Stage IV. Fourteen patients with Stage I and II disease underwent radical hysterectomy with pelvic lymph node dissection. In four, the operation was preceded by intracavitary radiation treatment. The patients with Stage II, III, and IV disease were treated with a combination of intracavitary radium, external beam radiation therapy, and chemotherapy. The 5-year survival rate was 14%. Four patients are alive, one with recurrent disease 50 months after diagnosis. Three patients free of disease have been followed up 26, 54, and 101 months, respectively.

CONCLUSIONS

Small cell carcinoma of the cervix is an aggressive tumor with a propensity for rapid recurrence; it is associated with high mortality.

Expression of laminin, collagen IV, fibronectin, and type IV collagenase in gastric carcinoma. An immunohistochemical study of 87 patients

BACKGROUND

This study attempted to determine if there is a pattern of matrix/matrix-degrading-enzyme immunoreactivity related to the morphologic types of gastric carcinoma or to their invasiveness.

METHODS

The authors performed an immunohistochemical study of the basement membrane antigens laminin and collagen IV, fibronectin, and Type IV collagenase in a series of 87 gastric carcinomas and their respective nodal metastases (n = 329).

RESULTS

Laminin expression was observed almost exclusively in carcinomas of the intestinal type. The expression of collagen IV was significantly higher in intestinal (52%) and atypical (44%) carcinomas than in diffuse (10%) carcinomas; collagen IV expression also was significantly correlated with lymphatic invasion and aneuploidy. Ninety percent of the carcinomas expressed fibronectin, mostly in the connective tissue at the invading edge of the tumors; fibronectin expression was significantly related to the expanding growth pattern of the neoplasms. Eighty-six percent of the tumors expressed Type IV collagenase, regardless of the histologic type or invasive properties. No relationship was observed between the expression of any of the antigens and the S-phase fraction of the tumors. No significant differences were found between the immunohistochemical profile of the primary tumors and their metastases.

CONCLUSIONS

The authors conclude that the expression of basement membrane antigens is related to the type of gastric carcinomas, rather than the cell differentiation or proliferative activity of the tumors. The putative prognostic meaning of the relationship between collagen IV immunoreactivity and aneuploidy and lymphatic invasiveness of the carcinomas remains to be clarified.

TP53 allele loss, mutations and expression in malignant melanoma

p53 alterations at the DNA, mRNA and protein levels were studied in tumour metastases sampled from 30 patients with malignant melanoma. Paraffin-embedded sections from these and an additional 12 patients were examined for the presence of p53 protein. TP53 gene aberrations were found in 7 of 30 (23%) of the patients, six of which showed loss of heterozygosity (LOH). Point mutations were detected in only two cases, one of which had LOH whereas the other was non-informative. Increased levels of p53 mRNA were present in only one tumour with, but in six cases without, detectable DNA abnormalities. Four of the latter and six tumours with normal transcript levels had immunohistochemically detectable levels of p53 protein. In 25 cases in which corresponding primary and metastatic lesions could be compared, closely similar immunoreactivity patterns were observed. Increased expression of the MDM2 gene was found in only one tumour in parallel with overexpression of p53. Altogether, the data indicate that inactivation of the p53 regulatory pathway is not of major significance in the tumorigenesis of malignant melanoma. However, a significant association was found between p53 immunoreactivity and the relapse-free period in patients with superficial spreading melanoma. That increased protein expression was predominantly found in tumours without DNA alterations might suggest a role for the wild-type p53 protein in restricting malignant cell proliferation in these cases.