Predictive value of ATP7b, BRCA1, BRCA2, PARP1, UIMC1 (RAP80), HOXA9, DAXX, TXN (TRX1), THBS1 (TSP1) and PRR13 (TXR1) genes in patients with epithelial ovarian cancer who received platinum-taxane first-line therapy.

To evaluate the predictive value of genes involved in resistance to platinum-taxane chemotherapy in patients with epithelial ovarian cancer (EOC). Microdissected formalin-fixed tumoral samples from 187 EOC patients' primary tumors (90 and 97 samples from matched patients in the experimental and validation sets, respectively) were analyzed. All specimens were analyzed for ATP7b, BRCA1, BRCA2, PARP1, UIMC1(RAP80), HOXA9, DAXX, TXN (TRX1), THBS1 (TSP1) and PRR13 (TXR1) mRNA expression by quantitative real-time PCR. Most of the patients (172 out of 187) received front-line carboplatin-paclitaxel regimen. Expression levels were correlated with overall (OS) and progression-free (PFS) survival by multivariate analysis. Patients with high TXN and THBS1 expression presented longer PFS (P=0.001 and P<0.001, respectively) and OS (P=0.024 and P<0.001, respectively). High TXR1 expression was associated with decreased PFS (P<0.001) and OS (P<0.001). Multivariate analysis demonstrated that high PRR13/low THBS1 expression was an independent factor for decreased PFS (hazards ratio: 1.94; 95% confidence interval (CI): 1.48-2.92; P=0.008) and OS (hazard ratio: 3.89; 95% CI: 2.16-6.87; P<0.001), whereas low TXN expression was correlated with decreased PFS (hazard ratio: 1.44; 95% CI: 1.05-2.84; P=0.043) and OS (hazard ratio: 2.38; 95% CI: 1.78-2.77; P=0.009). These findings indicate that PRR13/THBS1 and TXN expression could be used for the prediction of resistance to treatment of EOC patients and, therefore, merit to be further evaluated.

Cytopathologic interpretation of ascites due to malignancy.

The diagnosis of metastatic cancer in peritoneal fluid is of great importance for the patient and the attending physician. A cytopathologist's responsibility is twofold: (1) to accurately identify malignant cells; (2) to interpret tumor type and if possible the site of its origin even in the absence of complete clinical history of other clues. The difficulty in the diagnosis of metastatic neoplasms in peritoneal fluid is due to 2 factors: (1) abnormal mesothelial cells or macrophages may simulate cancer cells, or may conceal tumor cells; and (2) peritoneal fluid constitutes a natural and hitherto inadequately explored medium of cell culture, in which neoplastic cells may proliferate free of the boundaries imposed upon them by the framework of organs and tissues. Immunocytochemistry (ICC) and molecular techniques are essential to establish an accurate diagnosis. From a great many points of view malignant peritoneal fluid is suitable for continuous study of cancer cells, thus providing knowledge about biologic aspects of human solid tumors.

BRAF mutations, microsatellite instability status and cyclin D1 expression predict metastatic colorectal patients' outcome.

BACKGROUND: The significance of BRAF mutations, microsatelite instability (MSI) status and cyclin D1 expression in patients with metastatic colorectal cancer (mCRC) was evaluated. METHODS: Primary tumours from 144 patients treated for mCRC were assessed for BRAF (V600E) mutation, MSI status and cyclin D1. The data were correlated with progression-free survival (PFS) and overall survival (OS). RESULTS: BRAF mutations were detected in 10 (out of 22, 45%) patients with MSI-H tumours compared with 2 (out of 122, 1.6%) in those with microsatellite stable tumours (P<0.001). The presence of BRAF mutations was correlated with cyclin D1 overexpression (7 out of 26 patients, 58% vs 5 out of 118 patients, 14%; P=0.001). Patients with BRAF-mutated primary tumours had a significantly decreased PFS (2.7 vs 9.8 months; P<0.001) and median OS (14 vs 30 months; P<0.001) than patients with wild-type (wt) tumours. Patients with MSI-H and BRAF-mutated tumours experienced significantly lower PFS (3.1 vs 11.4 months; P=0.008) and OS (14.5 vs 35.5 months; P=0.004) than patients with MSI-H and BRAF wt tumours. Similarly, BRAF mutations and cyclin D1 overexpression were correlated with decreased PFS (3.1 vs 8.6 months; P=0.03) and OS (17.8 vs 39.2 months; P=0.01). CONCLUSION: BRAF V600E mutations are associated with MSI-H status and cyclin D1 overexpression and characterize a subgroup of patients with poor prognosis.

Prognostic and predictive value of common mutations for treatment response and survival in patients with metastatic colorectal cancer.

BACKGROUND: We address the prognostic and predictive value of KRAS, PIK3CA and BRAF mutations for clinical outcomes in response to active agents in the treatment of metastatic colorectal cancer (mCRC). METHODS: We determined KRAS, BRAF and PIK3CA mutations in tumours from 168 patients treated for mCRC at two institutions. All patients received 5-FU-based first-line chemotherapy and treatment outcome was analysed retrospectively. RESULTS: KRAS, BRAF and PIK3CA mutations were present in 62 (37%), 13 (8%) and 26 (15%) cases, respectively. Multivariate analysis uncovered BRAF mutation as an independent prognostic factor for decreased survival (hazard ratio (HR) 4.0, 95% confidence interval (CI) 2.1-7.6). In addition, patients with BRAF-mutant tumours had significantly lower progression-free survival (PFS: HR 4.0, 95% CI 2.2-7.4) than those whose tumors that carried wild-type BRAF. Among 92 patients treated using chemotherapy and cetuximab as salvage therapy, KRAS mutation was associated with lack of response (P=0.002) and shorter PFS (P=0.09). BRAF (P=0.0005) and PIK3CA (P=0.01) mutations also predicted reduced PFS in response to cetuximab salvage therapy. CONCLUSIONS: These results underscore the potential of mutational profiling to identify CRCs with different natural histories or treatment responses. The adverse significance of BRAF mutation should inform patient selection and stratification in clinical trials.

A Case Presentation of a Patient with Microsatellite Instability and BRAF Mutant Metastatic Colon Cancer and Bibliography Update.

This is a case of a patient who presented to the emergency department with acute abdominal pain due to bowel obstruction. An extended right hemicolectomy with ileosigmoid anastomosis due to an obstructing mass on the splenic flexure was urgently performed. During operation, liver and peritoneal lesions were detected and samples were also sent for histological analysis. Pathology report was consistent with poorly differentiated mucinous adenocarcinoma with signet ring cells; peritoneal lesions were confirmed histologically as metastatic. Genetic testing revealed the BRAFV600E mutation and mismatch repair deficiency (dMMR). After progressing on 1st line chemotherapy, the patient has a continuing and long-lasting partial response to 2nd line treatment with pembrolizumab.

Coexistance of a well differentiated liposarcoma and dedifferentiated low grade myxofibrosarcoma of the scrotum. A rare case and review of the literature.

Liposarcoma is a malignant soft tissue sarcoma usually located in the thigh or the posterior peritoneum in an adult. However, the occurrence of liposarcoma, and indeed a coexistance with scrotal myxofibrosarcoma, is rare. We present an interesting case of a 56-year old male who presented with an inguinal hernia. During the operation a massive fibro-elastic mass located within the left scrotum was noticed which deposited the testicle upward by displacing it into a sack rather than the penis. The mass did not come into contact with the spermatic cord but alongside it the existence of the blood vessels of the mass was found. The histopathological examination revealed a well differentiated liposarcoma along with dedifferentiated low grade myxofibrosarcoma.

Correlation of heat shock protein (HSP70) expression with cell proliferation (MIB1), estrogen receptors (ER) and clinicopathological variables in invasive ductal breast carcinomas.

The aim of our study was to evaluate the relationship between the expression of HSP70 protein, cell proliferation, the expression of ER receptors and the clinicopathological variables Grade and LNS in breast invasive human tumors along with the role of HSP70 protein in the prognosis of human breast cancer. A strong association between HSP70 expression and ER content, in agreement with previous data, was found which revealed a statistically significant association between HSP70 positivity and ER expression (p<0.008) in 50 cases of invasive primary human breast cancers. We also found a strong correlation between HSP70 expression, Grade and LNS of invasive ductal breast carcinomas. This suggests that the expression of HSP70 plays a significant role in the progression of human breast cancer, and might prove useful in many other malignancies as an important marker for the outcome of the disease.

Potential role of FLT3-ligand in the angiogenic process of multiple myeloma.

The aim of the study was to evaluate serum levels of FLT3-ligand (FLT3-L), a soluble molecule in bone marrow (BM), participating actively in hematopoiesis, in relation with angiogenic factors in multiple myeloma (MM) patients. We measured, in 70 patients with active MM and in 38 of them who responded to conventional therapy, serum levels of FLT3-L, along with known angiogenic factors, such as VEGF, endoglin, TNF-alpha and HGF (with ELISA) and BM microvascular density (MVD), estimating the immunohistochemical expression of CD31. All pre-treatment values were higher in active MM patients compared to controls (p<0.001 for all cases), in parallel with both International Staging System and Durie-Salmon stages (p<0.001 for all cases). Moreover, levels of FLT3-L correlated positively with all soluble angiogenic factors, as well with MVD (p<0.0001 for all cases). Post-treatment values of FLT3-L decreased significantly in responders to therapy (p<0.001). The underlying relation of MM angiogenesis with FLT3-L may result from the fact that BM microvasculature is a major source of FLT3-L, both in BM niche and probably in peripheral blood. Our results suggest that serum levels of FLT3-L may be used as angiogenic marker in MM patients.

Urocortin in human gastric mucosa: relationship to inflammatory activity.

The presence of CRH and urocortin (Ucn), members of the CRH family of neuropeptides, was examined in human gastric biopsies from normal controls and in patients with active gastritis from Helicobacter pylori (H. pylori) and after eradication treatment. RT-PCR analysis showed the presence of the Ucn transcript in biopsies (obtained by gastroscopy) from normal and inflamed gastric mucosa, whereas the CRH transcript was not detectable. Immunoreactive (ir-) Ucn was localized (by immunohistochemistry) in gastric epithelial cells and in inflammatory elements of the surrounding negative for Ucn gastric stroma. The level of ir-Ucn was higher in gastric biopsies from the group of patients with active H. pylori gastritis than in normal controls (10.4 +/- 1.8 vs. 2.0 +/- 1.3 pg/ micro g total protein; P < 0.001). After the apparent eradication of H. pylori infection (by clinical and morphological criteria) ir-Ucn levels increased dramatically to 43.1 +/- 9.8 pg/ micro g total protein, (P < 0.001) compared with pretreatment values. Interestingly, nonresponders to the eradication treatment did not show any significant change in ir-Ucn levels (18.7 +/- 12.3 pg/ micro g total protein) compared with their pretreatment values. In conclusion, our data suggest that in human gastric epithelium Ucn is present and plays an important physiological role, whereas CRH is absent. In addition, and in contrast to what has been found for CRH in ulcerative colitis, a highly significant, but negative, correlation has been found between Ucn levels and gastric inflammation, suggesting that Ucn may exert an antiinflammatory effect in gastric mucosa.

Changing pattern of cytokeratin 7 and 20 expression from normal epithelium to intestinal metaplasia of the gastric mucosa and gastroesophageal junction.

It is currently unclear whether intestinal metaplasia at the esophagogastric junction and in the distal esophagus represent a continuum of the same underlying disease process, i.e., gastroesophageal reflux, or constitute different entities with a different pathogenesis. Biopsies below the Z line might show specialized epithelium in some patients and the question is whether this is another form of short segment Barrett's esophagus or whether it is related to a generalized atrophic process of the stomach. Data from recent studies regarding the expression of cytokeratin CK7 and CK20 in intestinal metaplasia (IM) found at the gastroesophageal junction are conflicting. Prompted by these data we undertook the present study: a) to evaluate the expression of CK7 and CK20 in IM of the gastric cardia and to compare the findings with those in patients with Barrett's esophagus and IM of the gastric corpus and antrum mucosa; and b) to evaluate the immunophenotype of non-intestinalized cardiac mucosa and to compare it with that of normal gastric epithelium. We studied the expression of CK7 and CK20 on biopsy specimens from patients with long-segment Barrett's esophagus (n=17) and surgical resection and biopsy specimens of gastric cardia (n=15), corpus (n=14) and antrum (n=22) from patients with histological evidence of IM. Eighty-four biopsy specimens from 42 patients (antrum n=15, corpus n=20, cardia n=7) without evidence of IM were studied as a control group. We observed an immunophenotype characterised by diffuse moderate to strong CK7 staining on the surface and crypt epithelium combined with strong CK20 staining on the surface and superficial part of the crypts in 94.1% (16/17) of the cases with long-segment Barrett's esophagus, but in none of the 36 cases with IM in distal stomach (antrum and corpus). IM in the gastric cardia expressed the immunophenotype seen in IM of the gastric mucosa in 93.3% (14/15) of the cases. On the other hand, normal cardiac epithelium expressed patchy strong CK7 staining on the surface epithelium and on both, superficial and deep parts of the pits combined with patchy strong CK20 staining on the surface epithelium and superficial pits, a feature permitting distinction of the normal cardiac epithelium from those of the normal gastric antrum and corpus epithelium. We conclude that the expression of cytokeratins 7 and 20 can be used to distinguish the origin of IM of the gastroesophageal junction. The CK7/20 immunophenotype of IM in the gastric cardia closely resembles that of the IM in the gastric antrum and corpus and is different from IM in long-segment Barrett's esophagus. In contrast, the CK7/20 immunophenotype of the cardiac epithelium is different from that of the gastric antrum and corpus mucosa, suggesting that cardiac epithelium might not be a native normal gastric epithelium but one that is acquired as a consequence of longstanding inflammation. Changing pattern of CK7 and CK20 expression from normal to intestinalized epithelium suggests that IM arising from cardiac epithelium might have distinctive features.

Diagnostic difficulty arising from rectal recovery in ulcerative colitis.

AIMS: To ascertain whether the dogma that a normal rectal biopsy precludes a diagnosis of ulcerative colitis is correct. METHODS: Rectal biopsy specimens from a prospective group of 24 asymptomatic patients, with an established diagnosis of ulcerative colitis, were examined in a blinded study alongside 10 normal rectal biopsy specimens from an age and sex matched patient cohort without ulcerative colitis. Each biopsy specimen was assessed by three pathologists and ascribed to one of four categories: normal; borderline abnormality (one or more minor nonspecific abnormalities which, when combined, did not fulfil the minimal acceptable criteria for a diagnosis of ulcerative colitis); minimal features of chronic ulcerative colitis; and unequivocal ulcerative colitis. RESULTS: Two patients with ulcerative colitis had normal biopsy specimens; nine specimens were categorised as borderline abnormality, one as showing the minimal changes of chronic ulcerative colitis, and 12 as having the typical changes of chronic ulcerative colitis. Thus, 11 (46%) of the 24 patients had a rectal biopsy specimen that was devoid of the acceptable attributes on which a diagnosis is established, despite a confident previous diagnosis. Ten of these 11 cases had disease limited to the rectum. Review of all previous histological biopsy specimens (n = 164) and clinical data, including drug treatment, failed to identify any attributes that might be prognostic markers for future rectal mucosal healing. CONCLUSIONS: A normal rectal biopsy specimen, though uncommon, may occur in longstanding colitis. Moreover, in 46% of these asymptomatic but established cases the degree of healing may preclude a diagnosis of ulcerative colitis without comprehensive clinical and radiological details. Pathologists need to be aware of this minimal end of the spectrum of disease.

Malignant melanoma of the penis.

A case of malignant melanoma of the penis is herein reported. Malignant melanoma of the penis is rare and accounts for a small percentage of malignant melanomas and of malignant penile lesions. The diagnosis is often delayed by the patient's reluctance to consult a physician and by the intrinsic difficulty in clinical diagnosis of such a rare neoplasm. The surgical treatment is not standardized and is shortly discussed. In general, prognosis is poor and most patients die within a few years due to distant metastasis.

Gastric Carcinoid in a Young Woman with Systemic Lupus Erythematosus and Atrophic Autoimmune Gastritis.

BACKGROUND: Gastric carcinoid is a rare tumour that is associated with chronic atrophic gastritis in the majority of cases. It usually occurs in the 6th or 7th decade of life and is rarely diagnosed in patients under 30 years of age. METHODS: We describe a case of multiple gastric carcinoids in a 23-year-old woman with systemic lupus erythematosus and atrophic autoimmune gastritis--an association that has not been reported previously. RESULTS: The combination of atrophic autoimmune gastritis and gastric carcinoid with other autoimmune disorders has rarely been reported in the English medical literature. CONCLUSION: The fact that it mostly concerns (relatively) young patients may suggest a potential causative relation between those autoimmune disorders and the early development of atrophic gastritis with hypergastrinaemia, which subsequently leads to the occurrence of gastric carcinoid tumours at a young age.

The expression of myc and ras oncogene protein in childhood lymphomas.

Paraffin sections from 21 cases of Hodgkin's disease (HD), 18 cases of non-Hodgkin's lymphomas (NHL) and 15 cases of reactive lymphadenitides occurring in children 3-15 years old were examined by immunohistochemistry for the presence of c-myc and pan-ras oncogene products. In all cases of childhood lymphomas studied c-myc protein was expressed. The highest percentage was in HD where in 29% of cases the percentage of positive cells was greater than 20%, while in only 6% of NHL cases this percentage was noted. In all cases of reactive lymphadenitides the number of cells where c-myc was expressed was less than 5%. The ras oncogene was also found in HD but with a lesser degree of positivity than c-myc. In 48% of these cases the number of positive cells ranged between 2 and 10%, while in NHL and in reactive lymphadenitides there was no positivity. The above results indicate a frequent expression of c-myc protein in childhood lymphomas. This could reflect either an implication of c-myc oncogene in the pathogenesis of these tumor or an epiphenomenon of lymphomagenesis reflecting the proliferation rate of tumor cell population. Molecular biology studies are needed to clarify this issue.

C-erbB-2: expression in patients with breast carcinoma in comparison to patients with benign breast diseases.

C-erbB-2 (Her-2 or c-neu) expression was studied by immunohistochemistry on FNA specimens of 20 breast ductal carcinomas, 20 fibroadenomas and 20 atypical fibrocystic lesions of the breast. Twelve cases of breast carcinomas, six fibroadenomas and five atypical fibrocystic lesions were found to display c-erbB-2 staining. A significant difference was found among c-erbB-2 index of breast carcinomas (mean 70,25), fibroadenomas (mean 43,83) and atypical fibrocystic disease (mean 37,4). We also found variations in c-erbB-2 expression, among individual cases of breast carcinomas, concerning the number and the intensity of carcinoma cells. It would be interesting to correlate these variations in c-erbB-2 expression with the prognosis of breast carcinomas.

MIB1 (Ki-67) expression in non-Hodgkin's lymphomas.

The MIB1 monoclonal antibody which is used as a marker of cell proliferation was studied by immunohistochemistry on formalin-fixed and paraffin embedded biopsy specimens of lymph nodes in 40 high- and 46 lowgrade cases of non-Hodgkin's lymphomas (NHL) classified according to the Kiel classification. All cases were found to display nuclear MIB1 staining. A statistically significant difference (P < 0.005) was found between high- and low grade NHLs and this indicates that the high- grade NHL display a higher proliferation rate than low grade. In addition, remarkable variations in MIB1 expression were found among individual cases of the same histological group. These data may suggest that MIB1 index can help in the individual approach of the proliferation rate of each tumour and this may be an important parameter in association with clinical and other laboratory parameters for predicting the biological behaviour of non-Hodgkin's lymphomas.

p53 protein expression in breast carcinomas. Comparative study with the wild type p53 induced proteins mdm2 and p21/waf1.

The aim was to investigate the pattern of expression of p53 protein and two wild-type (wt) p53-induced proteins (mdm2 and p21/waf1), as an indirect way of assessing p53 gene status in breast carcinomas. Formalin-fixed paraffin embedded tissue from 102 cases of breast carcinomas comprising mostly ductal carcinomas (88 cases) was stained by immunohistochemistry for p53, mdm2 and p21/waf1 proteins. We found p53, mdm2 and waf1/p21 protein expression in 33/102, 20/102 and 38/102 breast carcinomas, respectively. Parallel p53/mdm2 protein expression was found in 9 cases. Five were also p21/waf1 positive. Discordant p53+/ mdm2-protein expression was found in 24 cases. Nine were p21/waf1 positive and the remaining fifteen were p21/waf1 negative. The patterns mdm2+/p53-/p21- and p21+/p53-(+)/mdm2- were found in 6 and 20 cases, respectively. Parallel p53/mdm2/p21 protein expression may represent breast carcinomas with wt p53 gene since mdm2 and p21 proteins are inducible by wt p53 gene. In these cases p53 protein expression may be due to stabilisation to mdm2 protein. This could be important in the pathogenesis of these cases since mdm2 may deregulate the p53-dependent growth suppressive pathway. Discordant p53+/mdm2-/p21- protein expression may represent breast carcinomas with p53 gene mutations unable to activate expression of mdm2 and p21 proteins. Breast carcinomas with p53+/mdm2/p21+ protein expression may have either wt p53 with deregulated mdm2 gene expression or mutated p53 gene with p53-independent p21 expression. Cases with only mdm2 expression may represent tumours with mdm2 gene amplification or overexpression and cases with only p21 expression may reflect p53-independent regulation of p21 protein.

Major histocompatibility complex (MHC)-I and MHC-II expression in Hodgkin's disease in relation to the presence of Epstein-Barr Virus (EBV).

We have investigated the immunohistochemical expression of beta2-microglobulin and HLA-DR proteins in Hodgkin's disease (HD) in relation to the expression of the EBV-encoded EBER1-2 mRNAs and the LMP-1 protein. beta2-microglobulin is expressed in association with MHC-I molecules on most nucleated cells and HLA-DR belongs to the MHC-II molecules which are expressed mostly on antigen-presenting cells. Formalin-fixed paraffin embedded tissue from 39 cases of lymphonodal HD were stained by immunohistochemistry for beta2-microglobulin, HLA-DR and LMP-1 proteins and by RNA in situ hybridization for EBER1-2 mRNAs. beta2-microglobulin positive staining was found in Reed-Sternberg and Hodgkin cells (HRS cells) in 18/39 cases of HD. HLA-DR positive staining was found in HRS cells in all cases of HD. EBER1-2 transcripts and LMP-1 protein were detected in HRS cells in 16/39 cases of HD. No correlation as found between the presence of EBER 1-2 transcripts or the LMP-1 protein and the detection of beta2-microglobulin and HLA-DR proteins in HD. Thus, EBV does not seem to use downregulation of MHC-I to avoid the T-cell cytotoxic immune response in HD. In addition, EBV does not seem to be the only factor responsible for the HLA-DR expression in HRS cells of HD, although it could participate in the induction of the expression of HLA-DR molecule in the EBV positive cases of HD.

Immunohistochemical expression of p53, bcl-2, mdm2 and waf1/p21 proteins in colorectal adenocarcinomas.

The present study was undertaken to examine the distribution of p53, p21, mdm-2 and bcl-2 protein expression in human colorectal adenocarcinomas in order to obtain combined information about the immunophenotypes characterising these tumours. Formalin-fixed, paraffin-embedded tissue sections from 52 cases of colorectal adenocarcinomas were stained using immunohistochemical methods for the detection of p53, p21/waf1, mdm2 and bcl-2 proteins. P53, p21/waf1, mdm2 and bcl-2 proteins were expressed in 35/52, 45/52, 9/52 and 27/52 cases, respectively. All nine mdm2+ cases expressed p53 and p21 proteins as well. The three patterns observed in p53/p21 expression were: p53+/p21+, p53+/p21- and p53-/p21+ in 28, 7, and 17 cases, respectively. Consequently, p53+/mdm2-/p21+, p53+/mdm-/p21- and p53-/mdm2-/p21+ immunophenotypes were expressed in 19, 7, and 17 cases respectively. Four patterns of p53/bcl2 expression were identified: p53+/bcl2+, 20 cases; p53+/bcl2-, 15 cases; p53-/bcl2+, 7 cases; p53-/bcl2-, 10 cases. It was noteworthy that 9 of the 10 p53-/bcl2-tumours had negative lymph node status. The present results suggest that both p53 dependent and p53-independent induction of p21 expression may be involved in the molecular mechanisms controlling these tumours. High expression of the p53 protein in colorectal carcinomas could be due not only to p53 gene mutations but also to binding to mdm2 protein which leads to p53 protein stabilisation. In addition, tumours with p53-/bcl2- immunophenotype are frequently associated to negative lymph node status and seem to be less aggressive.

Expression of p53, p21, mdm2, Rb, bax and Ki67 proteins in lymphomas of the mucosa-associated lymphoid (MALT) tissue.

We have investigated by immunohistochemistry 38 cases of B-cell MALT-NHL comprising 23 high grade (HG) and 15 low grade-(LG) tumours for the expression of p53, mdm2, p21, Rb, Ki67, bcl2 and Bax proteins. P53, mdm2 and p21 proteins were found in at least 5% of the tumour cells in 13/23, 2/23 and 11/23 HG tumours, respectively. These proteins were detected in very rare tumour cells in LG tumours. The following patterns were recorded in HG tumours: p53+/p21+/mdm2+ (2 cases), p53+/p21+/mdm2- (7 cases), p53+/p21-/mdm2- (4 cases), p53-/p21-/mdm2- (18 cases) and p53-/p21+/mdm2-(2 cases). Proliferative Ki67 index and Rb protein expression were higher in HG than in LG MALT-NHL. Bcl2 protein was expressed in all LG MALT-NHL, whereas only 2/23 HG MALT-NHL were bcl2 positive in most tumour cells. Bax protein was expressed in all MALT-NHL with HG tumours being positive in higher proportion of tumour cells than LG tumours. These findings show that significant expression of p53, mdm2, p21,Ki67 and Rb proteins occurs more frequently in aggressive histotypes of MALT-NHL. The parallel Rb/Ki67 expression suggests that Rb protein expression in MALT-NHL is normally regulated in relation to the proliferative growth fraction of the tumours. The pattern p53+/p21+/mdm2 +/- may represent MALT-NHL with wild type (wt) p53 gene since mdm2 and p21 proteins are inducible by wt p53 gene. The pattern p53+/mdm2-/p21-may represent MALT-NHL with p53 gene mutations unable to activate expression of mdm2 and p21 proteins. MALT-NHL with the p53-/mdm2-/p21 + pattern may be consistent with p53-independent p21 expression. Bax protein expression in all MALT-NHL suggests a role for this protein in the pathogenesis of these tumours.