E-Cadherin gene promoter hypermethylation in primary human gastric carcinomas.

BACKGROUND: E (epithelial)-cadherin, the cell adhesion molecule also considered a potential invasion/metastasis suppressor, is mutationally inactivated in nearly half of all undifferentiated-scattered (diffuse-type) gastric carcinomas. In addition, silencing of E-cadherin by CpG methylation within its promoter region has been reported in several gastric carcinoma cell lines. We investigated the methylation status of the E-cadherin promoter region in 53 primary human gastric carcinomas. METHODS: Hypermethylation of the E-cadherin promoter was determined by utilizing methylation-specific polymerase chain reaction (PCR)-single-strand conformation polymorphism (MSP-SSCP) analysis followed by direct sequencing of PCR products. Expression of E-cadherin was studied by western blot analysis. All statistical tests were two-sided. RESULTS: Hypermethylation of the E-cadherin promoter was evident in 27 (51%) of 53 primary gastric carcinomas examined by MSP-SSCP. It occurred more frequently in carcinomas of the undifferentiated-scattered type (in 15 [83%] of 18) than in other histologic subtypes (in 12 [34%] of 35) (P =.0011, Fisher's exact test), and it was present at similar rates in early (in six [60%] of 10) versus advanced (in 21 [49%] of 43) carcinomas (P =.73, Fisher's exact test). Methylation occurring at all cytosine-guanosine sequences (CpGs) near the transcriptional start site was confirmed in six of six tumors examined by bisulfite-DNA sequencing, including two early gastric carcinomas. In addition, loss or diminished expression of E-cadherin was confirmed by western blotting in four of the six tumor tissues demonstrating hypermethylation. CONCLUSIONS: The E-cadherin promoter frequently undergoes hypermethylation in human gastric cancers, particularly those of the undifferentiated-scattered histologic subtype. E-cadherin promoter hypermethylation is associated with decreased expression and may occur early in gastric carcinogenesis.

Clinical implications of K-ras mutations in malignant epithelial tumors of the endometrium.

Tumorigenesis in humans and experimental animals appears to involve the activation of ras protooncogenes for a number of organ systems and seems to be important to the development of the metastatic phenotype in several model systems. Clinically, the presence of activated ras protooncogenes has been reported to be a negative prognostic factor in the myelodysplastic syndrome and in adenocarcinoma of the lung. In the present study we examined 49 cases of endometrial carcinoma for mutations in the first exon of K-ras using the polymerase chain reaction and direct sequencing. Mutations in codon 12 or 13 of K-ras were detected in 6 of 49 cases (12.2%). These six cases consisted of five endometrioid endometrial carcinomas, each of which had a mutation in codon 12, and one case of clear cell carcinoma, which had a mutation in codon 13. In our study the presence of mutations in K-ras appeared to be an unfavorable prognostic factor. Three of six patients with the mutation died during follow-up, while only 7% of the 43 patients without K-ras mutations expired during this same period. In multivariate analysis using the Cox proportional hazard model, K-ras activation appeared to be an independent risk factor when compared with clinical stage, depth of myometrial invasion, and patient age. Thus, our findings support the hypothesis that K-ras protooncogene activation plays an important role in determining the aggressiveness of endometrial carcinoma.

Prognostic significance of p53 overexpression in endometrial cancer.

Abnormalities of p53, a tumor suppressor gene, have been considered to play an important role in tumorigenesis. Clinically, overexpression of p53 has been reported to correlate with poor prognosis in several types of tumors. In this study, we examined 221 cases of endometrioid endometrial carcinoma for overexpression of p53 using immunohistochemistry in patients with a median follow-up of 41 months. Immunohistochemical analysis was performed with monoclonal antibody pAb1801. Overexpression of p53 was detected in 47 of 221 cases (21.3%). There was a statistically significant correlation between p53 overexpression and poor prognosis (P < .0001). In the early stages of cancer (stages 1 and 2), p53 was overexpressed in 11 of 22 patients (50%) who died or had a recurrence during follow-up. In contrast, overexpression was detected in only 14.7% of the 156 disease-free patients during the same period (P < .0001). In advanced stages (stages 3 and 4), tumors from patients with recurrent disease had a higher frequency of overexpression (41.2%; 7 of 17) than those of disease-free patients (23.1% 6 of 26). However, the difference between these frequencies was not statistically significant. In multivariate analysis using the Cox proportional hazard model, p53 overexpression was an independent risk factor when compared with clinical stage, nuclear grade, and patient age. Our results indicate that p53 immunohistochemical evaluation of the most common form of endometrial cancer may be useful in identifying cases of aggressive carcinoma, especially in the early stages.

Distinct methylation patterns of two APC gene promoters in normal and cancerous gastric epithelia.

The adenomatous polyposis coli (APC) tumor suppressor gene is mutationally inactivated in both familial and sporadic forms of colorectal cancers. In addition, hypermethylation of CpG islands in the upstream portion of APC, a potential alternative mechanism of tumor suppressor gene inactivation, has been described in colorectal cancer. Because a subset of both gastric and colorectal cancers display the CpG island methylator phenotype, we hypothesized that epigenetic inactivation of APC was likely to occur in at least some gastric cancers. APC exhibits two forms of transcripts from exons 1A and 1B in the stomach. Therefore, we investigated CpG island methylation in the sequences upstream of exons 1A and 1B, i.e., promoters 1A and 1B, respectively. We evaluated DNAs from 10 gastric cancer cell lines, 40 primary gastric cancers, and 40 matching non-cancerous gastric mucosae. Methylated alleles of promoter 1A were present in 10 (100%) of 10 gastric cancer cell lines, 33 (82.5%) of 40 primary gastric cancers, and 39 (97.5%) of 40 noncancerous gastric mucosae. In contrast, promoter 1B was unmethylated in all of these same samples. APC transcripts from exon 1A were not expressed in nine of the 10 methylated gastric cancer cell lines, whereas APC transcripts were expressed from exon 1B. Thus, expression from a given promoter correlated well with its methylation status. We conclude that in contrast to the colon, methylation of promoter 1A is a normal event in the stomach; moreover, promoter 1B is protected from methylation in the stomach and thus probably does not participate in this form of epigenetic APC inactivation.

The validation of new aromatase monoclonal antibodies for immunohistochemistry--a correlation with biochemical activities in 46 cases of breast cancer.

Intratumoral aromatase is a therapeutic target for the treatment of post-menopausal estrogen-dependent breast cancers. Therefore, reliable methods should be developed for routine application for the detection of intratumoral aromatase. Immunohistochemistry (IHC) is considered one of the most suitable methods in this regard. A multi-centre collaborative group has been established to generate and validate new aromatase monoclonal antibodies. We have selected two monoclonal antibodies, #677 against native aromatase protein and F2 against formalin-fixed protein for this purpose. With these two monoclonal antibodies 43 cases of invasive ductal carcinoma, which had been previously assayed for aromatase activity by product isolation methodology, were immunostained in three laboratories in UK, USA and Japan and independently evaluated by three pathologists (H.S., T.A. and S.G.S.). Staining of malignant epithelium, adipose tissue, normal/benign and stromal compartments of the tumors were assessed by estimating the proportion of positive staining cells and the relative intensity of staining in this fashion. Immunoreactivity could be detected in each component of the tissue specimens but a significant positive correlation with biochemical activity was detected only in malignant epithelium stained with 677 not in other components with #677 and not in any of the components. Staining using F2 as a primary antibody did not produce a positive correlation in any components with aromatase activity. These results suggest that we now have a monoclonal antibody against aromatase (#677) which may be used to stain archival materials. A methodology and scoring system is recommended whereby staining significantly correlates with aromatase activity of the resected tissue specimens of breast cancer.

Aromatase and 17 beta-hydroxysteroid dehydrogenase type 1 in human breast carcinoma.

The in situ formation of estradiol plays an important role in the development and biological behavior of human breast cancer Aromatase and 17 beta-hydroxysteroid dehydrogenase type 1 (17 beta-HSD type 1) are two principal enzymes involved in in situ estradiol production. We evaluated the expression of aromatase and 17 beta-HSD type 1 by immunohistochemistry in 41 cases of invasive breast carcinoma (19 lobular and 22 ductal). We then examined the correlation among the expression of these enzymes, estrogen (ER) and progesterone (PR) receptor status, Ki67 labeling index of carcinoma cells, age, and the clinical stage of the patients. Marked aromatase immunoreactivity was observed in stromal cells around carcinomatous glands in 32 of 41 cases (78%), and 17 beta-HSD type 1 immunoreactivity was detected in carcinoma cells in 23 of 41 cases (56%). There was a significant correlation observed between expression of 17 beta-HSD type 1 and aromatase in invasive lobular carcinoma (P = 0.0119), but not in invasive ductal carcinoma. There was an inverse correlation between aromatase and ER status in invasive ductal carcinoma (P = 0.0213), but not in invasive lobular carcinoma. No other correlations were observed among 17 beta-HSD type 1, aromatase, PR, ER, clinical stage, age, and Ki67 labeling indexes. Aromatase and 17 beta-HSD are not always expressed simultaneously in human breast carcinoma, but their simultaneous expression is more frequent in invasive lobular carcinoma than invasive ductal carcinoma. Consequently, different mechanisms may be involved in the regulation of expression of these two enzymes in human breast carcinoma.

Oral contraceptives as risk factors for cervical adenocarcinomas and squamous cell carcinomas.

To assess the hypothesis that oral contraceptives (OCs) increase the risk of cervical adenocarcinomas, we conducted a six-center case-control study of 124 patients with adenocarcinomas, 139 with squamous cell carcinomas, and 307 population controls. Women between the ages of 18 and 69 who were newly diagnosed with cervical adenocarcinomas between 1992 and 1996 were eligible. Healthy female controls and a second case group of incident cervical squamous cell carcinomas were matched to the adenocarcinoma cases. All participants were interviewed regarding OCs, other risk factors for cervical carcinoma, and utilization of cytological screening, and a PCR-based test determined HPV genotype of cervical samples for both case groups and controls. Use of OCs was positively and significantly associated with adenocarcinomas and positively but weakly associated with squamous cell carcinomas. Associations between OCs and invasive adenocarcinomas (n = 91), squamous cell carcinoma in situ (n = 48), and invasive squamous cell carcinomas (n = 91) disappeared after accounting for HPV infection, sexual history, and cytological screening, but a positive association remained between current use of OCs and cervical adenocarcinoma in situ (n = 33). This association persisted after stratification by screening and sexual history and after restriction according to HPV status, but small numbers made it difficult to exclude detection bias, selection bias, or residual confounding by HPV as potential explanations Current OC use was associated with cervical adenocarcinomas in situ, but we saw no other evidence that OCs independently increase the risk of cervical carcinomas.

Intraoperative cytologic evaluation of lipid in the diagnosis of parathyroid adenoma.

Analysis of intraoperative air-dried imprints or smears of 20 cases of parathyroid adenoma revealed that the cells of the parathyroid adenomas did not contain extra- or intracellular lipid, but the cytologic material from accompanying normal or atrophic parathyroid glands had large amounts of intracellular lipid and variable amounts of extracellular lipid. Thus, rapid intraoperative cytologic preparation is not only effective in determining whether the specimen is parathyroid or not, but also in specifying the nature of the individual parathyroid glands. These observations again confirm that intraoperative cytologic evaluation of parathyroid tissue is an effective and important pathologic consultation method during parathyroid exploration.

Intraoperative pathologic consultation. An audit of 1,000 recent consecutive cases.

In order to assess the accuracy of the intraoperative consultation, or "frozen section," a retrospective review of 1,000 consecutive intraoperative consultations was performed. We present these data as a quality assurance assessment and as an update to a body of older literature examining the accuracy of the frozen section. The indications for intraoperative consultation and types of specimen submitted have changed in recent years, and these changes are related to the results in the present study. The increasingly important role of intraoperative cytology as an adjunct to and, in many cases, a replacement for frozen section is also emphasized.

Reproducibility of the mitosis count in the histologic diagnosis of smooth muscle tumors of the uterus.

In order to ascertain the reproducibility of the mitosis count in histologic tumor diagnosis, a reference set of 10 microscopic slides from smooth muscle tumors of the uterus was shown to six different pathologists, who were asked to record the number of mitotic figures per 10 high power fields in the most active region of each slide. The results, when tubulated, revealed considerable observer variation in this supposedly objective and quantitative diagnostic criterion. The diagnosis of benignity or malignancy, based on this criterion alone, were unamimous in only four of the 10 cases, whereas the diagnoses based on a constellation of histologic criteria were unanimous in all cases and correlated well with the subsequent clinical evolution of those cases with follow-up data. Possible reasons for the lack of reproducibility of the mitosis count are discussed. We conclude that a qualitative estimation of mitotic activity is helpful as one of the diagnostic and prognostic criteria in the assessment of uterine and other smooth muscle tumors, but that it cannot be used as the sole criterion for distinguishing benign from malignant tumors.

Medullary carcinoma of the breast: a clinicopathologic study with appraisal of current diagnostic criteria.

Fifty-three cases of mammary carcinoma originally diagnosed as medullary carcinoma (MC) or infiltrating duct carcinoma (IDC) with medullary features were reviewed and reclassified using the strictly defined histologic criteria applied a decade ago by Ridolfi et al. Our study interval (1961 to 1982) allowed for a minimum follow-up of 5 years for each patient, with a mean follow-up period of 7.2 years. When reclassified, 24 tumors fulfilled the criteria for MC, 16 tumors were determined to be atypical MC, and ten tumors were found to be IDC; the observed 5-year survival rates were 95%, 80%, and 70%, respectively. These findings confirmed those of other investigators, that when specific criteria are applied, MC proves to be a form of mammary carcinoma with a favorable prognosis. However, we also found that when tumors were excluded from the MC category solely on the basis of in situ carcinoma, focal marginal infiltration, or a sparse mononuclear infiltrate, the survival rate of these patients was similar to that of patients in the medullary category. Thus, we propose that one of these criteria alone should not suffice to exclude the diagnosis of MC. On the other hand, tumors with two or more of these atypical features, or with extensive marginal infiltration, no mononuclear cellular infiltrate, and/or less than 75% syncytial growth, should be classified as IDC with medullary features. Typical MC with bland nuclei or a focal microglandular growth pattern only were not observed in this series; however, these findings should probably also cause a tumor to be classified in the IDC category. By dividing our cases into two rather than three groups, we found a statistically significant difference between the survival rates of 94% and 64% for MC (34 tumors) and IDC (14 tumors), respectively. Although the latter figure probably exceeds the survival rate for IDC without medullary features, the difference does not appear great enough to warrant a separate diagnostic category.

Ovarian tumors associated with atypical endometriosis.

We present five cases in which ovarian neoplasms (three clear cell carcinomas, two endometrioid carcinomas) were associated--and in four cases contiguous--with atypical glandular epithelial changes in endometriosis. This association has not been reported previously in the ovary, but four cases of extragonadal malignant tumors have been noted to occur with or after atypical endometriosis. We propose that a diagnosis of atypical endometriosis be followed by careful long-term observation of the patient to detect possible subsequent development of neoplasia.

Immunolocalization of c-myc oncoprotein in mucinous and serous adenocarcinomas of the ovary.

Activation of c-myc oncogene has been reported in increasing numbers of human ovarian carcinomas and appears to play a role in the biologic behavior of the neoplasms. We have studied the immunohistochemical localization of p-62c-myc, the gene product of c-myc, in 44 cases of serous and mucinous cystadenoma, adenocarcinoma of low malignant potential, and invasive adenocarcinoma, using a monoclonal antibody raised to a synthetic human p62c-myc sequence (Myc 1-6E10). Both serous and mucinous cystadenomas demonstrated a higher frequency of nuclear localization than did carcinomas, which showed much greater cytoplasmic staining, while tumors of low malignant potential showed an intermediate pattern. However, the observed differences did not reach statistical significance. No significant correlation was observed between intracellular localization patterns of p62c-myc and histologic and nuclear grades and mitotic activity in the cases of carcinoma. Great care should be taken in the interpretation of immunohistochemical analysis of oncogene products, especially when attempting to correlate the findings with biologic tumor behavior.

Carcinosarcoma (malignant mixed müllerian (mesodermal) tumor) of the female genital tract: immunohistochemical and ultrastructural analysis of 28 cases.

In an attempt to clarify the histogenesis of carcinosarcoma (malignant mixed müllerian tumor) of the female genital tract, 20 uterine and eight ovarian tumors were studied by light microscopy, transmission electron microscopy, and immunohistochemistry. Cytokeratins (MAK-6 and AE1:AE3) and epithelial membrane antigen were detected in the epithelial component of all tumors and in the stromal component of 15 cases (55%). Vimentin was detected in the stromal component of all cases and was focally positive in the epithelial component of 18 cases (69%). Tumors showing rhabdomyosarcomatous or chondrosarcomatous differentiation were positive for myoglobin and S-100 protein, respectively. At the ultrastructural level epithelial cells were observed in tight clusters (usually surrounded by a basal lamina), in loose aggregates, and singly (sometimes spindle shaped), and were surrounded by cells displaying variable differentiation. The closest examples of "hybrid" epithelial/stromal cells were those with a prominent rough endoplasmic reticulum, cytoplasmic projections, poorly formed intercellular junctions, and an incomplete basal lamina. The observations support the view that carcinosarcomas of the female genital tract could represent examples of biphasic (metaplastic) carcinomas.

Loss of heterozygosity on chromosome 11q13 in lobular lesions of the breast using tissue microdissection and polymerase chain reaction.

Demonstration of identical allelic loss on chromosome 11q13 in synchronous in situ (DCIS) and invasive ductal (IDC) breast carcinoma has provided molecular evidence of the progression of DCIS to IDC. We investigated loss of heterozygosity (LOH) at chromosome 11q13 in the spectrum of "marker/premalignant" and "malignant" lobular lesions of the breast, including atypical lobular hyperplasia (ALH), lobular carcinoma in situ (LCIS), and infiltrating lobular carcinoma (ILC). Thirty-eight cases with various combinations of ALH, LCIS, and ILC were studied. Synchronous ductal lesions were present in 9 of 38 cases. Areas of interest were specifically isolated by tissue microdissection. The extracted DNA was amplified by polymerase chain reaction (PCR) and analyzed with two polymorphic markers for chromosome 11q13 (INT2 and PYGM). LOH at 11q13 was identified in ILC and LCIS in approximately one third of informative cases. LCIS in association with ILC showed a loss in 50% of cases, whereas pure LCIS in the absence of ILC had a much lower frequency of LOH, which was comparable to that of pure ALH. These results suggest that LOH on chromosome 11q13 may play an important role in development of ILC, similar to that of IDC from DCIS/ADH. Additionally, frequent LOH in ILC and LCIS associated with ILC and a significantly lower and comparable frequency of LOH in LCIS without ILC and ALH implies that genetic alteration(s) on chromosome 11q13 may be important in the transition of LCIS to ILC. LOH was detected in three of nine synchronous ductal lesions (one IDC and two DCIS), confirming our earlier findings and indicating that lobular and ductal neoplasia in the breast show some similar genetic changes. We hypothesize that LOH may help in separating morphologically similar yet genetically different subgroups of ALH and LCIS into one group with genetic changes and an increased potential to progress to invasive cancer and another group, the "marker" lesions of LCIS/ALH, that remain stable or possibly regress.

Placental site nodule occurring in a fallopian tube.

The placental site nodule (PSN), a recently described benign lesion of intermediate trophoblast, is usually an incidental finding in younger women. It is a well-circumscribed, round to oval lesion that is extensively hyalinized and immunohistochemically stains for cytokeratin, placental alkaline phosphatase (PLAP), human placental lactogen (HPL) and, focally, for human chorionic gonadotropin (HCG) and epithelial membrane antigen (EMA). Thus far, the cases reported have been found in endometrial curettage or hysterectomy specimens. The pathogenesis of PSN is yet to be ascertained; however, there is wide acceptance of the fact that it represents a remnant of the placental implantation site. If this is indeed the case, it should not be surprising to find PSN occurring at sites of ectopic gestation. We describe herewith a case in which PSN was found in a fallopian tube segment resected in a postpartum tubal ligation.

Infiltrating cribriform carcinoma of the breast: a distinctive clinicopathologic entity.

All cases of primary breast carcinoma seen at the George Washington University Medical Center between 1971 and 1975 and between 1981 and 1986 were reviewed, and examples of pure and mixed infiltrating cribriform carcinoma (ICC) were identified. The relative frequency of ICC did not change significantly from the earlier to the later study period. As previously reported by Page et al, there was a tendency for ICC to be associated with foci of tubular carcinoma and of intraductal carcinoma (often but not always of cribriform type). Pure ICC (defined as showing no other infiltrating carcinoma type), predominant ICC with lesser amounts of infiltrating carcinoma of any other type and any quantitative combination of ICC and tubular carcinoma metastasized to axillary lymph nodes frequently, but almost never to more than three nodes, in contradistinction to tumors composed of infiltrating duct carcinoma (IDC) not otherwise specified and less than 50% ICC, and a control group of IDC, which significantly more often involved four or more nodes. ICC cases were estrogen-receptor-positive in 100% and progesterone-receptor-positive in 69% of the cases. Five-year survival rates for eligible cases were 100% for pure and greater than or equal to 50% ICC, 88% for less than 50% ICC, and 78.3% for the IDC controls. ICC is a histologically and clinically distinctive type of mammary carcinoma that should be separated from IDC and other tumor types.

Advanced stage transitional cell carcinoma of the ovary.

Primary transitional cell carcinoma (TCC) of the ovary has been recently recognized as a separate subtype of epithelial cancer. It has been proposed that recognition of such tumors is important on clinical grounds because of a favorable response to chemotherapy and an improved patient survival. The authors reviewed the histological and clinicopathologic findings of 58 patients with advanced stage (stages III and IV) ovarian cancer with a view to determining the frequency of TCC and confirming the favorable prognosis. Of these cases, 15 (26%) were reclassified as TCC; 13 were predominantly TCC, and 2 had a mixed pattern with approximately 50% of the tumor being TCC. TCC patients ranged in age from 44 to 70 years of age (mean, 57). Ten of the patients had stage III disease, and five were stage IV. The tumor was unilateral in 2 cases and bilateral in 11 (2 unknown). Tumor size varied between 3 and 23 cm. Of the stage III patients, five were optimally debulked, and five had residual disease. All patients received the same type of chemotherapy. The median overall survival was 28 months. There was no significant difference in the clinical outcome of patients with TCC compared with that of patients with serous carcinomas. These data suggest that TCC does not confer a favorable prognosis or better response rate to chemotherapy.

Immature teratoma of the ovary with a neural component ("solid" teratoma). A clinicopathologic study of 20 cases.

Twenty cases of immature teratoma of the ovary with a neural component are analyzed. A plea is made for use of the nomenclature adopted from the new World Health Organization classification of ovarian tumors, the past confusion over terminology and histogenesis of this rare tumor is discussed. All the primary tumors in the present series contained at least some immature tissues (predominantly of neural origin) and were thus graded from 1 to 3 according to the criteria of Thurlbeck and Scully. No grade 0 tumors ("benign solid teratomas") were identified. We believe that thorough sectioning almost always insures the identification of immature elements. The prognosis was closely related to the histologic grade, but correlated poorly withthe clinical stage, the latter being influenced by the common finding (25 per cent of the cases in this series) of peritoneal implants composed exclusively of mature glial tissue, which is associated with a benign clinical evolution. This phenomenon of maturation or differentiation appears to be the rule rather than the exception in this tumor, since implants are usually of better or equal differentiation when compared with their primary tumors and older patients tend to have lower grade tumors than younger patients. Since the majority of patients with this tumor are young, primary surgical therapy should be conservative, unilateral salpingooophorectomy often being sufficient. Spontaneous or operative rupture of the tumor capsule carries an increased risk of subsequent dissemination. We have noted impressive clinical responses in patients with disseminated tumors of a high histologic grade after treatment with triple chemotherapy (vincristine, actinomycin D, and cyclophosphamide) but do not recommend adjuvant therapy in patients with only grade 0 implants.

Microinvasion in low malignant potential tumors of the ovary.

The presence of microinvasion (Mi) has not previously been investigated in nonserous low malignant potential (LMP) tumors of the ovary. In serous LMP tumors (SLMP), Mi has not worsened the prognosis compared with usual SLMP in previous reports. In a retrospective clinicopathologic review of 126 cases of serous and mucinous LMP (MLMP) tumors of the ovary, the authors identified 14 cases with Mi: seven of 72 SLMP, four of 44 mucinous intestinal LMP (MILMP), and three of 10 mucinous müllerian LMP (MMLMP). Tumors with Mi resembled usual LMP histologically except for small foci (up to 0.2 cm) in the stroma consisting predominantly of single cells or small clusters of cells, sometimes in a cribriform pattern. In SLMP-Mi, the cells had eosinophilic cytoplasm, and the stromal reaction was minimal/absent. In MILMP-Mi and MMLMP-Mi, nuclear staining was paler; the stroma often showed a fibrous reaction or edema, especially in MILMP-Mi. All 14 patients had follow-up (2.2 to 18.6 years) and were without evidence of disease. Careful screening of both mucinous and serous ovarian LMP can show Mi. Mi foci should be distinguished from true stromal invasion, pseudoinvasion, endothelial cells, decidual cells and histiocytes, and pseudomyxoma in mucinous LMP. Mi does not seem to worsen prognosis in MLMP and SLMP tumors of the ovary.