Efficacy and Safety of Radiation Segmentectomy with 90Y Resin Microspheres for Hepatocellular Carcinoma

Background Limited data are available on radiation segmentectomy (RS) for treatment of hepatocellular carcinoma (HCC) using yttrium 90 (90Y) resin microsphere doses determined by using a single-compartment medical internal radiation dosimetry (MIRD) model. Purpose To evaluate the efficacy and safety of RS treatment of HCC with 90Y resin microspheres using a single-compartment MIRD model and correlate posttreatment dose with outcomes. Materials and Methods This retrospective single-center study included adult patients with HCC who underwent RS with 90Y resin microspheres between July 2014 and December 2022. Posttreatment PET/CT and dosimetry were performed. Adverse events were assessed using the Common Terminology Criteria for Adverse Events, version 5.0. Per-lesion and overall response rates (ie, complete response [CR], objective response, disease control, and duration of response) were assessed at imaging using the Modified Response Evaluation Criteria in Solid Tumors, and overall survival (OS) was assessed using Kaplan-Meier analysis. Results Among 67 patients (median age, 69 years [IQR, 63-78 years]; 54 male patients) with HCC, median tumor absorbed dose was 232 Gy (IQR, 163-405 Gy). At 3 months, per-lesion and overall (per-patient) CR was achieved in 47 (70%) and 41 (61%) of 67 patients, respectively. At 6 months (n = 46), per-lesion rates of objective response and disease control were both 94%, and per-patient rates were both 78%. A total of 88% (95% CI: 79 99) and 72% (95% CI: 58, 90) of patients had a per-lesion and overall duration of response of 1 year or greater. At 1 month, a grade 3 clinical adverse event (abdominal pain) occurred in one of 67 (1.5%) patients. Median posttreatment OS was 26 months (95% CI: 20, not reached). Disease progression at 2 years was lower in the group that received 300 Gy or more than in the group that received less than 300 Gy (17% vs 61%; P = .047), with no local progression in the former group through the end of follow-up. Conclusion Among patients with HCC who underwent RS with 90Y resin microspheres, 88% and 72% achieved a per-lesion and overall duration of response of 1 year or greater, respectively, with one grade 3 adverse event. In patients whose tumors received 300 Gy or more according to posttreatment dosimetry, a disease progression benefit was noted. © RSNA, 2024 Supplemental material is available for this article.

EUS imaging for the diagnosis of nonalcoholic fatty liver disease

BACKGROUND AND AIMS

EUS is increasingly used to evaluate patients with liver disease, but its role in assessing hepatic steatosis has not been reported. The goal of our study was to assess the accuracy of EUS for diagnosing hepatic steatosis.

METHODS

We identified all patients who underwent EUS-guided liver biopsy sampling at our institution. All digitally stored EUS liver images were reviewed by a single radiologist, who rated the severity of liver echogenicity using a 4-point US scale. Liver biopsy specimens for all study patients were reviewed by a single liver pathologist, who rated them for steatosis and fibrosis using Nonalcoholic Steatohepatitis Clinical Research Network criteria. Receiver operator characteristic curves were used to assess the diagnostic accuracy of EUS for hepatic steatosis for all patients and in a subgroup analysis for obese and nonobese patients.

RESULTS

During the study period, 76 patients underwent EUS-guided liver biopsy sampling. The average age of study patients was 56.5 years, 50% were women, and 43.2% were obese. The accuracy for EUS for the diagnosis of hepatic steatosis was .8 (95% confidence interval [CI], .7-.89). The accuracy of EUS for the diagnosis of hepatic steatosis in obese patients was .93 (95% CI, .8-.99) and in nonobese patients was .69 (95% CI, .54-.83). For obese patients, EUS had a positive predictive value of 89.7% and a negative predictive value of 75%. The finding of course echotexture on EUS had an accuracy of 79% for the diagnosis of grade 3 fibrosis or cirrhosis.

CONCLUSIONS

EUS is a useful tool for the diagnosis of hepatic steatosis, particularly in obese patients in whom abdominal US has modest accuracy.

Neoadjuvant Yttrium-90 Transarterial Radioembolization with Resin Microspheres Prescribed Using the Medical Internal Radiation Dose Model for Intrahepatic Cholangiocarcinoma

PURPOSE

To evaluate outcomes of patients with intrahepatic cholangiocarcinoma (iCCA) undergoing neoadjuvant yttrium-90 (⁹⁰Y) transarterial radioembolization (TARE) with resin microspheres prescribed using the Medical Internal Radiation Dose (MIRD) model.

MATERIALS AND METHODS

This retrospective institutional review board-approved study included 37 patients with iCCA treated with ⁹⁰Y-TARE from October 2015 to September 2020. The primary outcome was overall survival (OS) from ⁹⁰Y-TARE. The secondary outcomes were progression-free survival (PFS), Response Evaluation Criteria In Solid Tumors 1.1 imaging response, and downstaging to resection. Patients with tumor proximity to the middle hepatic vein (<1 cm) and/or insufficient future liver remnant were treated with neoadjuvant intent (n = 21). Patients were censored at the time of surgery or at the last follow-up for the Kaplan-Meier survival analysis.

RESULTS

For 31 patients (69 years; interquartile range, 64-74 years; 20 men [65%]) included in the study, the first-line therapy was ⁹⁰Y-TARE for 23 (74%) patients. Imaging assessment at 6 months showed a disease control rate of 86%. The median PFS was 5.4 months (95% confidence interval [CI], 3-not reached). The PFS was higher after first-line ⁹⁰Y-TARE (7.4 months [95% CI, 5.3-not reached]) than that after subsequent ⁹⁰Y-TARE (2.7 months [95% CI, 2-not reached]) (P = .007). The median OS was 22 months (95% CI, 7.3-not reached). The 1- and 2-year OS rates were 60% (95% CI, 41%-86%) and 40% (95% CI, 19.5%-81%). In patients treated with neoadjuvant intent, 11 of 21 patients (52%) underwent resections. The resection margins were R0 and R1 in 8 (73%) and 3 (27%) of 11 patients, respectively. On histological review in 10 patients, necrosis of ≥90% tumor was achieved in 7 of 10 patients (70%).

CONCLUSIONS

First-line ⁹⁰Y-TARE prescribed using the MIRD model as neoadjuvant therapy for iCCA results in good survival outcome and R0 resection for unresectable patients.

Deficiency of miR-208a Exacerbates CCl4-Induced Acute Liver Injury in Mice by Activating Cell Death Pathways

Acute liver injury (ALI) is associated with multiple cellular events such as necrosis, apoptosis, oxidative stress and inflammation, which can lead to liver failure. In this study, we demonstrate a new role of microRNA (miR)‐208a in ALI. ALI was induced in wild‐type (WT) and miR‐208a knockout (KO) mice by CCl₄ administration. Increased alanine aminotransferase and decreased hepatic miR‐208a levels were found in WT mice after acute CCl₄ treatment. Histopathological evaluations revealed increased necrosis and decreased inflammation in miR‐208a KO compared with WT mice after CCl₄ treatment. CCl₄ treatment induced a higher alanine aminotransferase elevation and increased numbers of circulating extracellular vesicles (exosomes and microvesicles) in miR‐208a KO compared with WT mice. We found increased CCl₄‐induced nuclear factor kappa B activation and tumor necrosis factor‐α induction and decreased monocyte chemoattractant protein 1 levels in miR‐208a KO compared with WT mice. Terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick‐end labeling assay indicated aggravated hepatic apoptosis and necrosis in CCl₄‐treated miR‐208a KO compared with WT mice. CCl₄ treatment induced a greater increase in cleaved caspase‐8, p18, and caspase‐3 in miR‐208a KO compared with WT mice. p53 is involved in various cell death pathways, including necrosis and apoptosis. Our in silico analysis revealed p53 as a predicted miR‐208a target, and we found enhanced p53 and cyclophilin D protein expressions in miR‐208a KO mice after CCl₄ treatment. Increased liver injury in miR‐208a KO mice was further associated with increased Bax (B cell lymphoma 2–associated X protein) and p21 expression. Our in vitro results indicated a role of miR‐208a in cell death. We found that CCl₄‐induced cytotoxicity was partially rescued by miR‐208a overexpression in RAW macrophages. Altogether, our results revealed a role of miR‐208a in ALI in mice and suggest a role for miR‐208a in regulating cell death.

Deficiency of fibroblast growth factor 21 (FGF21) promotes hepatocellular carcinoma (HCC) in mice on a long term obesogenic diet

OBJECTIVE

Non-alcoholic fatty liver (NAFL) associated with obesity is a major cause of liver diseases which can progress to non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Fibroblast growth factor 21 (FGF21) plays an important role in liver metabolism and is also a potential marker for NAFL. Here we aimed to test the effect of FGF21 deficiency on liver pathology in mice consuming a conventional high fat, high sucrose (HFHS) obesogenic diet for up to 52 weeks.

METHODS

C57BL6 WT and FGF21 KO mice were fed a conventional obesogenic diet and were evaluated at 16 and 52 weeks. Evaluation included metabolic assessment, liver pathology, and transcriptomic analysis.

RESULTS

With consumption of HFHS diet, FGF21 deficient mice (FGF21 KO) develop excess fatty liver within 16 weeks. Hepatic pathology progresses and at 52 weeks FGF21 KO mice show significantly worse fibrosis and 78% of mice develop HCC; in contrast only 6% of WT mice develop HCC. Well differentiated hepatocellular carcinomas in FGF21 KO mice were characterized by expanded hepatic plates, loss of reticulin network, cytologic atypia, and positive immunostaining for glutamine synthetase. Microarray analysis reveals enrichment of several fibroblast growth factor signaling pathways in the tumors.

CONCLUSIONS

In addition to attenuating inflammation and fibrosis in mice under a number of dietary challenges, we show here that FGF21 is required to limit the progression from NAFL to HCC in response to prolonged exposure to an obesogenic diet. The induction of hepatic FGF21 in response to the high fat, high sucrose obesogenic diet may play an important role in limiting progression of liver pathology from NAFL to HCC.

Fibroblast growth factor 21 limits lipotoxicity by promoting hepatic fatty acid activation in mice on methionine and choline-deficient diets

BACKGROUND & AIMS

Nonalcoholic fatty liver disease is a common consequence of human and rodent obesity. Disruptions in lipid metabolism lead to accumulation of triglycerides and fatty acids, which can promote inflammation and fibrosis and lead to nonalcoholic steatohepatitis. Circulating levels of fibroblast growth factor (FGF)21 increase in patients with nonalcoholic fatty liver disease or nonalcoholic steatohepatitis; therefore, we assessed the role of FGF21 in the progression of murine fatty liver disease, independent of obesity, caused by methionine and choline deficiency.

METHODS

C57BL/6 wild-type and FGF21-knockout (FGF21-KO) mice were placed on methionine- and choline-deficient (MCD), high-fat, or control diets for 8-16 weeks. Mice were weighed, and serum and liver tissues were collected and analyzed for histology, levels of malondialdehyde and liver enzymes, gene expression, and lipid content.

RESULTS

The MCD diet increased hepatic levels of FGF21 messenger RNA more than 50-fold and serum levels 16-fold, compared with the control diet. FGF21-KO mice had more severe steatosis, fibrosis, inflammation, and peroxidative damage than wild-type C57BL/6 mice. FGF21-KO mice had reduced hepatic fatty acid activation and β-oxidation, resulting in increased levels of free fatty acid. FGF21-KO mice given continuous subcutaneous infusions of FGF21 for 4 weeks while on an MCD diet had reduced steatosis and peroxidative damage, compared with mice not receiving FGF21. The expression of genes that regulate inflammation and fibrosis were reduced in FGF21-KO mice given FGF21, similar to those of wild-type mice.

CONCLUSIONS

FGF21 regulates fatty acid activation and oxidation in livers of mice. In the absence of FGF21, accumulation of inactivated fatty acids results in lipotoxic damage and increased steatosis.

Hepatitis C virus-specific T-cell-derived transforming growth factor beta is associated with slow hepatic fibrogenesis

Hepatitis C virus (HCV)-specific immune effector responses can cause liver damage in chronic infection. Hepatic stellate cells (HSC) are the main effectors of liver fibrosis. TGFβ, produced by HCV-specific CD8(+) T cells, is a key regulatory cytokine modulating HCV-specific effector T cells. Here we studied TGFβ as well as other factors produced by HCV-specific intrahepatic lymphocytes (IHL) and peripheral blood cells in hepatic inflammation and fibrogenesis. This was a cross-sectional study of two well-defined groups of HCV-infected subjects with slow (≤ 0.1 Metavir units/year, n = 13) or rapid (n = 6) liver fibrosis progression. HCV-specific T-cell responses were studied using interferon-gamma (IFNγ)-ELISpot ±monoclonal antibodies (mAbs) blocking regulatory cytokines, along with multiplex, enzyme-linked immunosorbent assay (ELISA) and multiparameter fluorescence-activated cell sorting (FACS). The effects of IHL stimulated with HCV-core peptides on HSC expression of profibrotic and fibrolytic genes were determined. Blocking regulatory cytokines significantly raised detection of HCV-specific effector (IFNγ) responses only in slow fibrosis progressors, both in the periphery (P = 0.003) and liver (P = 0.01). Regulatory cytokine blockade revealed HCV-specific IFNγ responses strongly correlated with HCV-specific TGFβ, measured before blockade (R = 0.84, P = 0.0003), with only a trend to correlation with HCV-specific IL-10. HCV-specific TGFβ was produced by CD8 and CD4 T cells. HCV-specific TGFβ, not interleukin (IL)-10, inversely correlated with liver inflammation (R = -0.63, P = 0.008) and, unexpectedly, fibrosis (R = -0.46, P = 0.05). In addition, supernatants from HCV-stimulated IHL of slow progressors specifically increased fibrolytic gene expression in HSC and treatment with anti-TGFβ mAb abrogated such expression.

CONCLUSION

Although TGFβ is considered a major profibrogenic cytokine, local production of TGFβ by HCV-specific T cells appeared to have a protective role in HCV-infected liver, together with other T-cell-derived factors, ameliorating HCV liver disease progression.

Levels of alanine aminotransferase confound use of transient elastography to diagnose fibrosis in patients with chronic hepatitis C virus infection

BACKGROUND & AIMS

Hepatic elastography (HE) is a noninvasive technique that measures liver stiffness and is used to diagnose hepatic fibrosis. It can help patients who are thought to have early-stage disease avoid a staging liver biopsy, but only when confounding variables that increase liver stiffness are excluded. Chronic inflammation from hepatitis C virus (HCV) infection is not considered to be one of these variables.

METHODS

We identified 684 patients with HCV and METAVIR fibrosis scores of 0-2 from a prospective, multi-institutional study of liver stiffness in 2880 patients with chronic liver disease. Patients were 49.6 ± 9.0 years old, 64.3% were male, and they had an average body mass index of 26.7 ± 4.1 kg/m(2).

RESULTS

In a multivariate analysis, inflammation (based on histologic analysis) and level of alanine aminotransferase (ALT) were associated with liver stiffness. The chances of a patient having a level of stiffness that indicates cirrhosis increased with grade of inflammation and level of ALT. By using a conservative 14.5-kPa cutoff for the diagnosis of cirrhosis, grade 3 inflammation had an odds ratio of 9.10 (95% confidence interval, 2.49-33.4). Likewise, levels of ALT greater than 80 and 120 IU/L had odds ratios of 3.84 (95% confidence interval, 2.10-7.00) and 4.10 (95% confidence interval, 2.18-7.69), respectively. The effect of the level of ALT persisted when analysis was restricted to patients with fibrosis scores of F0 to F1.

CONCLUSIONS

In patients with HCV infection and early-stage fibrosis, increased levels of ALT correlate with liver stiffness among patients in the lowest strata of fibrosis (METAVIR scores 0-2). Patients without fibrosis but high levels of ALT could have liver stiffness within the range for cirrhosis. Inflammation should be considered a confounding variable in analysis of liver stiffness.

Hepatitis C genotype 4: What we know and what we don't yet know

Hepatitis C virus genotype 4 (HCV-4) is the most common variant of the hepatitis C virus (HCV) in the Middle East and Africa, particularly Egypt. This region has the highest prevelance of HCV worldwide, with more than 90% of infections due to genotype 4. HCV-4 has recently spread in several Western countries, particularly in Europe, due to variations in population structure, immigration, and routes of transmission. The features of HCV-4 infection and the appropriate therapeutic regimen have not been well characterized. This review discusses the virology, epidemiology, natural history, histology, clinical data, and treatment options for patients with HCV-4 infections. Early reports on the treatment of patients with chronic HCV-4 with conventional interferon (IFN)-alpha monotherapy indicated poor rates of sustained viral response (SVR), which improved slightly when combined with ribavirin. Pegylated IFN and ribavirin combination therapy has dramatically improved the response rates, with recent clinical trials showing rates that exceed 60%. These data can now be used as a platform for further research to define optimal treatment duration and predictors of SVR in patients with HCV-4 infection.

CONCLUSION

HCV-4 infection is spreading beyond its strongholds in Africa and the Middle East. Recent clinical trials show that HCV-4 is not difficult to treat, as the response to treatment may be at an intermediate level compared with genotype 1 and genotypes 2 or 3. Tailored treatment options that are comparable to the treatment approaches for genotype 1, 2, and 3 patients to optimize treatment for each patient are now being developed.

Long-term docosahexaenoic acid therapy in a congenic murine model of cystic fibrosis

We used a congenic C57Bl/6J cystic fibrosis transmembrane conductance regulator (Cftr)(-/-) mouse model, which develops cystic fibrosis (CF)-like pathology in all organs, to evaluate the short- and long-term therapeutic effects of dietary docosahexaenoic acid (DHA). Thirty-day-old Cftr(-/-) mice and wild-type littermates were randomized to receive a liquid diet with or without DHA (40 mg/day). Animals were killed for histological and lipid analysis after 7, 30, and 60 days of therapy. DHA had no significant therapeutic or harmful effect on the lung, pancreas, or ileum of the Cftr(-/-) mice or their wild-type littermates. In contrast, dietary DHA resulted in highly significant amelioration of the severity of liver disease in the Cftr(-/-) mice, primarily a reduction in the degree of peri-portal inflammation. Additionally, these detailed measurements confirm our previous findings that Cftr(-/-) mice have significant alterations in the pancreas (except external acinar diameter), ileum, liver, lung, and salivary (except sublingual) glands at all ages compared with their age-matched wild-type littermates. In conclusion, inhibition of cytokines and/or eicosanoid metabolism and release of endogenous inhibitors of inflammation by DHA may account for the anti-inflammatory effects in the liver of this congenic murine model of CF. The potential therapeutic benefits of DHA in severe CF-associated liver disease remain to be explored.

Induction of colitis in cftr-/- mice results in bile duct injury

It is unknown why some patients with inflammatory bowel disease develop primary sclerosing cholangitis. We have recently shown that patients with primary sclerosing cholangitis have an increased prevalence of mutations in the gene responsible for cystic fibrosis (CFTR) compared with individuals with inflammatory bowel disease alone. Our aim was to examine whether induction of colitis by oral dextran leads to bile duct injury in mice heterozygous or homozygous for mutations in CFTR. The effect of oral administration of docosahexaenoic acid to correct a fatty acid imbalance associated with cystic fibrosis was also examined to determine whether this would prevent bile duct inflammation. Wild-type mice and mice heterozygous and homozygous for CFTR mutations were given dextran orally for 14 days to induce colitis. Bile duct injury was quantitated by blinded histological scoring and measurement of serum alkaline phosphatase activity. The effect of pretreatment with docosahexaenoic acid for 7 days was examined. Treatment of mice with 100 mg dextran/day for 9 days followed by 85 mg/day for 5 days resulted in a significant increase in bile duct injury as determined by histological scoring in homozygous cystic fibrosis mice compared with wild-type mice (P = 0.005). The bile duct injury seen in cystic fibrosis mice was reflected in a threefold increase in serum alkaline phosphatase (P = 0.0006). Pretreatment with oral docosahexaenoic acid decreased both histological evidence of bile duct injury and serum alkaline phosphatase levels. In the setting of colitis, loss of CFTR function leads to bile duct injury.

High resolution anoscopy findings for men who have sex with men: inaccuracy of anal cytology as a predictor of histologic high-grade anal intraepithelial neoplasia and the impact of HIV serostatus

We compared the pathological diagnoses obtained by anal Papanicolaou (Pap) smear with those obtained by anal biopsy or by surgical excision for 153 men who have sex with men (MSM). Analysis of these paired specimens showed that anal Pap smears were an inaccurate predictor of high-grade anal dysplasia, regardless of human immunodeficiency virus (HIV) serostatus. The presence of any abnormal anal cytological finding indicates a potential for high-grade dysplasia on histological examination of MSM.

Clinicopathologic characterization of squamous-cell carcinoma arising from pilonidal disease in association with condylomata acuminatum in HIV-infected patients: report of two cases

Pilonidal disease is a common acquired condition believed to arise from penetration of short hairs into the subcutaneous tissue that induces a cyst or sinus formation. Malignant degeneration is rare and is typically seen only after decades of antecedent disease presence. Condylomata acuminatum in association with pilonidal disease have been described in two prior case reports, however, the coexistence of condyloma with pilonidal disease complicated by malignant degeneration has not been previously reported. Condylomata have known potential for malignant degeneration and are correlated with human papilloma virus infection, with certain serotypes of higher oncogenic potential. Coinfection with human immunodeficiency virus and human papilloma virus is associated with higher rates of anal neoplasia. We report two cases of human immunodeficiency virus-infected patients with the constellation of pilonidal disease, condylomata acuminatum, and subsequent malignant degeneration into squamous-cell carcinoma. In contrast to other case reports in the literature, these two patients had considerably shorter antecedent periods of pilonidal disease before malignant degeneration was detected. Both cases also had intractable courses. We conclude that the existence of condylomata acuminatum and pilonidal disease in an immunocompromised patient may represent a more ominous condition than solitary pilonidal disease. Therefore, careful inspection of the pilonidal area in human immunodeficiency virus-infected patients presenting with condylomata is important and earlier intervention should be considered. Moreover, further evaluation of the prevalence of squamous-cell carcinoma arising from pilonidal disease complicated by condylomata, particularly in the immunosuppressed, is warranted.

Chemoembolization for hepatocellular carcinoma: epinephrine followed by a doxorubicin-ethiodized oil emulsion and gelatin sponge powder

PURPOSE

This study evaluates chemoembolization (CE) of the liver with minimal vasoconstriction followed by selective intraarterial delivery of an emulsion of iopamidol, doxorubicin, and ethiodized oil and temporary occlusion of hepatic artery with gelatin sponge powder in patients with hepatocellular carcinoma.

PATIENTS AND METHODS

Since 1988, 30 patients with nonresectable hepatocellular carcinoma underwent CE with the above protocol. Intraarterial epinephrine (0.5-1 microgram diluted in 10 mL of saline) was rapidly injected directly into the proper hepatic artery or selectively into the right or left hepatic arteries and was followed by 40-60 mg of doxorubicin dissolved in 10 mL of iopamidol and emulsified in 20 mL of ethiodized oil. The chemoembolic mixture was injected at the rate of arterial flow. Liver function and clotting parameters were monitored three times a day until there was a downward trend toward preembolic levels. Computed tomography (CT) was performed immediately after embolization and at 1-3-month intervals. Embolization was repeated when CT demonstrated recurrent or progressive disease.

RESULTS

Disease recurred or progressed in 11 patients at 2-17 months after embolization. CE was repeated in four patients; one individual underwent three embolizations. Re-embolization was performed up to 14 months after initial embolization (median, 10 months). Five patients (16.7%) died within 1 month of embolization. Ten patients died at 3-33 months after CE. Two of these patients died of cirrhosis at 6 and 14 months, without evidence of recurrent tumor. Fifteen patients remain alive 5-28 months after CE. Kaplan-Meier estimation of probability of survival curves demonstrates a median survival of 14 months. Sixty-one percent of patients were alive at 1 year and 36% at 2 years after the procedure.

CONCLUSION

CE with use of the above technique is effective for palliating inoperable hepatocellular carcinoma. It causes a significant prolongation of survival over the expected 18-24 weeks in untreated patients; this may occur because high doses of chemotherapeutic agents are delivered and come in contact with the tumor for a longer period, followed by ischemia brought about by temporary arterial occlusion.

Occult axillary lymph node metastases in "node-negative" breast carcinoma

The presence of occult axillary nodal metastases was evaluated in 159 patients with "node-negative" invasive breast carcinoma. Multiple additional levels of the lymph nodes were examined with hematoxylin-eosin staining and keratin immunostaining. Occult nodal metastases were detected in 50 (31%) patients; of these, 28 (17%) were detectable by hematoxylin-eosin stain alone, while the other 22 (14%) consisted of mostly single cells or very small clusters and required immunostaining for detection. The size of the metastatic deposit was < or = 0.2 mn in 31 (19%) patients and greater than 0.2 mm in 19 (12%) patients. Occult nodal metastasis correlated with the presence of peritumoral lymphatic invasion (P = .02) and was seen more frequently with larger tumor size, increased microvasculature, and aneuploidy. As a group occult metastases had no significant prognostic impact. However, patients with metastases measuring greater than 0.2 mm had significantly worse recurrence (P = .02), disease-free survival (P = .04), and overall survival (P = .07) rates; those with metastases detectable by hematoxylin-eosin stain alone also had a less favorable, although not significant, outcome. In contrast, patients with occult metastases that were < or = 0.2 mm or that were detected only by immunostaining had a survival rate comparable to and in fact slightly higher than that of the group without occult metastasis; 23 of these patients were without recurrence after a median follow-up of 11 years. Extension into perinodal soft tissue was an unfavorable feature. In a multivariate analysis peritumoral lymphovascular invasion and increased microvasculature were the most important prognostic parameters, and the presence of occult metastases greater than 0.2 mm was no longer significant. Our data suggest that occult metastases < or = 0.2 mm, especially those consisting of single cells, do not add useful prognostic information, and immunohistochemical studies to detect them are probably unnecessary. Larger metastases and extranodal involvement may have important prognostic value, but in this study they accounted for only 20% of patients who had recurrences or 6% of the total population. This underscores the importance of using more than one prognostic parameter in evaluating breast carcinoma.