Induction TPF followed by concomitant treatment versus concomitant treatment alone in locally advanced head and neck cancer. A phase II-III trial.

BACKGROUND: Platinum-based chemoradiation (CCRT) is the standard treatment for Locally Advanced Head and Neck Squamous-Cell Carcinoma (LAHNSCC). Cetuximab/RT (CET/RT) is an alternative treatment option to CCRT. The efficacy of induction chemotherapy (IC) followed by chemoradiation compared to chemoradiation alone has not been demonstrated in randomized clinical trials. The goals of this phase II-III trial were to assess: (i) the overall survival (OS) of IC versus no-induction (no-IC) and (ii) the Grade 3-4 in-field mucosal toxicity of CCRT versus CET/RT. The present paper focuses on the analysis of efficacy. MATERIALS AND METHODS: Patients with LAHNSCC were randomized to receive concomitant treatment alone [CCRT (Arm A1) or CET/RT (Arm A2)], or three cycles of induction docetaxel/cisplatin/5 fluorouracil (TPF) followed by CCRT (Arm B1) or followed by CET/RT (Arm B2). The superiority hypothesis of OS comparison of IC versus no-IC (Arms B1 + B2 versus A1 + A2) required 204 deaths to detect an absolute 3-year OS difference of 12% (HR 0.675, with 80% power at two-sided 5% significance level). RESULTS: 414 out of 421 patients were finally analyzed: 206 in the IC and 208 in the no-IC arm. Six patients were excluded because of major violation and one because of metastatic disease at diagnosis. With a median follow-up of 44.8 months, OS was significantly higher in the IC arm (HR 0.74; 95% CI 0.56-0.97; P = 0.031). Complete Responses (P = 0.0028), Progression Free Survival (P = 0.013) and the Loco-regional Control (P = 0.036) were also significantly higher in the IC arm. Compliance to concomitant treatments was not affected by induction TPF. CONCLUSIONS: IC followed by concomitant treatment improved the outcome of patients with LAHNSCC without compromising compliance to the concomitant treatments. The degree of the benefit of IC could be different according to the type of the subsequent concomitant strategy. CLINICAL TRIAL NUMBER: NCT01086826, www.clinicaltrials.gov.

Are strong opioids equally effective and safe in the treatment of chronic cancer pain? A multicenter randomized phase IV 'real life' trial on the variability of response to opioids.

BACKGROUND: Guidelines tend to consider morphine and morphine-like opioids comparable and interchangeable in the treatment of chronic cancer pain, but individual responses can vary. This study compared the analgesic efficacy, changes of therapy and safety profile over time of four strong opioids given for cancer pain. PATIENT AND METHODS: In this four-arm multicenter, randomized, comparative, of superiority, phase IV trial, oncological patients with moderate to severe pain requiring WHO step III opioids were randomly assigned to receive oral morphine or oxycodone or transdermal fentanyl or buprenorphine for 28 days. At each visit, pain intensity, modifications of therapy and adverse drug reactions (ADRs) were recorded. The primary efficacy end point was the proportion of nonresponders, meaning patients with worse or unchanged average pain intensity (API) between the first and last visit, measured on a 0-10 numerical rating scale. (NCT01809106). RESULTS: Forty-four centers participated in the trial and recruited 520 patients. Worst pain intensity and API decreased over 4 weeks with no significant differences between drugs. Nonresponders ranged from 11.5% (morphine) to 14.4% (buprenorphine). Appreciable changes were made in the treatment schedules over time. Each group required increases in the daily dose, from 32.7% (morphine) to 121.2% (transdermal fentanyl). Patients requiring adjuvant analgesics ranged from 68.9% (morphine) to 81.6% (oxycodone), switches varied from 22.1% (morphine) to 12% (oxycodone), discontinuation of treatment from 27% ( morphine) to 14.5% (fentanyl). ADRs were similar except for effects on the nervous system, which significantly prevailed with morphine. CONCLUSION: The main findings were the similarity in pain control, response rates and main adverse reactions among opioids. Changes in therapy schedules were notable over time. A considerable proportion of patients were nonresponders or poor responders. CLINICAL TRIAL REGISTRATION: NCT01809106 (https://clinicaltrials.gov/ct2/show/NCT01809106?term=cerp&rank=2).

Laparoscopic total fallopian tube removal at the time of bilateral salpingo-oophorectomy in BRCA2 positive women.

About 10% of all serous ovarian cancer has BRCA1 and/or BRCA2 mutations. Recent data showed that following the SEE FIM protocol it is possible to evidence more fimbriae cancers. Due to those studies, fallopian tube cancer in recent years has become the predominant site of cancer in BRCA1 and/or 2 mutation carriers. The pathological study of the fallopian tube is not complete during salpingo-oophorectomy because a small part (intramural site) is situated inside the uterus. In this case report we demonstrate how it is possible to remove the tubes entirely for pathological analysis without hysterectomy by laparoscopic surgery.

Incidence of prostate cancer in Sicily: results of a multicenter case-findings protocol.

OBJECTIVE: To establish the incidence of prostate cancer (PCa) in Sicily in patients who entered an early detection protocol. METHODS: From February 2002 to February 2004, 16,298 subjects aged 40-75 entered the protocol. Patients with suspicious DRE, PSA>10 ng/ml, PSA

A new nested primer pair improves the specificity of CK-19 mRNA detection by RT-PCR in occult breast cancer cells.

Reverse transcription polymerase chain reaction (RT-PCR) of cytokeratin-19 (CK-19) has been widely used to detect small numbers of circulating malignant epithelial cells in the bone marrow or the peripheral blood of patients with breast cancer. However, a high percentage of false positive results has been recorded and conflicting reports question the clinical relevance of this technical approach. We demonstrate that the use of a new nested primer pair for CK-19 RT-PCR avoids false positive results without affecting the sensitivity of the assay. Our experiments were carried out using MCF-7 cells alone or mixed with peripheral blood mononuclear cells (PBMNC) of healthy donors. The results were also validated in a large series of healthy donors and in a preliminary study on a limited number of patients with breast cancer, thus suggesting that our assay is feasible for application in the clinical evaluation of occult malignant epithelial cells.

[Alcohol sclerotherapy of biliary cysts. Our experience]. / Traitement par alcoolisation des kystes biliaires. Expérience personnelle sur 13 cases.

AIM OF THE STUDY: To evaluate if percutaneous ethanol injection treatment, introduced twelve years ago as palliative therapy for inoperable hepatocellular carcinoma, can be used with curative intent to treat biliary cysts with good results. MATERIALS AND METHODS: For the study were observed 13 symptomatic patients (M 4; F 9 - age 38-71, medium 54 years). All the patients were treated by percutaneous alcoholization under ultrasonographic control. RESULTS: Better technique and protocol standardisation give us the possibility to utilise percutaneous ethanol injection like a good treatment for symptomatic patients. CONCLUSIONS: Easy technique, low cost and very small number of complications gives to percutaneous ethanol injection the possibility to become the gold standard for the treatment of biliary cysts.

CD 34 expression in chronic and neoplastic liver diseases.

BACKGROUND: Capillarisation of hepatic sinusoids is a well recognized phenomen occurring in long standing liver disease, in hepatic cirrhosis as well as in hepatocellular carcinoma. To study immunohistochemically the expression and distribution of CD34 in chronic liver disease and hepatocellular carcinoma in order to evaluate the possible diagnostic implication of this marker. METHODS: Sixty-five samples of liver tissue showing normal liver, different degrees of chronic inflammation, cirrhosis and histological features of hepatocellular adenoma and carcinoma (HCC) were included in the study. The specimens were fixed in formalin and embedded in paraffin and an immunohistochemical investigation was performed by the standard avidin-biotin-peroxidase complex method with CD34. RESULTS: The sinusoids of normal liver showed no immunoreactivity. The sinusoids of liver affected by different degrees of chronic active hepatitis showed no or focal immunostaining for CD34; an increased immunoreactivity was observed in the periportal sinusoids of the cirrhotic nodules whereas diffuse and strong staining was observed in the overall HCC as well as in the hepatocellular adenoma tested. CONCLUSIONS: In HCC, immunoreactivity for CD34 represents an effective method to evaluate angiogenesis and to distinguish well-differentiated HCC from non-neoplastic liver. Its role in clinical stage and prognostic evaluation needs further investigation.

Conditioned medium from MCF-7 cell line induces myofibroblast differentiation, decreased cell proliferation, and increased apoptosis in cultured normal fibroblasts but not in fibroblasts from malignant breast tissue.

We studied the effect of conditioned medium (CM) obtained from cultures of oestrogen-receptor positive breast cancer MCF7 cell line on the differentiation, proliferation and apoptosis patterns of cultured breast fibroblasts from normal interstitial and malignant stromal tissue. Fibroblasts were grown in the presence or absence of CM and examined for the differentiation pattern by immunofluorescence and Western blotting procedures, for proliferation profile by Ki67 expression, and for apoptosis by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling technique. Monoclonal antibodies specific for non-muscle (NM), smooth muscle (SM) lineage and differentiation markers were applied to these cultures. CM is able to induce a SM-like differentiation in interstitial fibroblasts, i.e., essentially myofibroblast formation. Fibroblasts from tumour stroma showed the presence of a small number of smooth muscle cells (SMC) along with a large number of myofibroblasts. Treatment of these cultures with CM was unable to change this pattern. Only normal fibroblasts were responsive to the proliferation/apoptotic-inhibitory effect of the CM. These data suggest that structural and functional differences exist between stromal fibroblasts from normal breast and breast cancer with respect to the responsiveness to soluble factors present in the CM. We hypothesize that the lack of in vitro sensitivity to CM shown by 'tumour' fibroblasts is the result of an in vivo inherent and stable phenotypic change on the fibroblasts surrounding breast tumour cells occurring via a paracrine mechanism.

Multimodal therapy of hepatocarcinoma: personal experience on 90 cases.

BACKGROUND/AIMS: In recent years, surgical and non-surgical options have been developed in the treatment of hepatocellular carcinoma in cirrhotic patients. We review our personal series from 1995-1999, in order to assess the choice of treatment. METHODOLOGY: Of 90 cases of hepatocellular carcinoma observed in the years 1995-1999, 15 underwent curative resective surgery; in 42 cases TAE, PEI or RITA were utilized (9 of them as multimodal therapy). In the remaining 33 patients any kind of therapy was scheduled. RESULTS: The mean survival of the 15 resected patients was 18 months, non-statistically better than RITA survival, compared by Log-Rank test. Perioperative mortality calculated in all procedures was 5.2% (2 pts surgery, 1 pt TAE). CONCLUSIONS: The high percentage of not treated hepatocellular carcinomas in our series is generally due to large tumor size diagnosed in advanced Child's stage. PEI, TAE and RITA have to be considered effective and safe for palliation for HCCs. However, surgical resection represents the curative therapy in selected cirrhotic patients affected by HCC.

Hypnosis in the treatment of anticipatory nausea and vomiting in patients receiving cancer chemotherapy.

AIMS AND BACKGROUND: In addition to nausea and vomiting following chemotherapy treatment, cancer patients can experience these side effects prior to a treatment session, the so-called anticipatory nausea and vomiting. As various psychological and neurophysiological aspects have been claimed to be implied in its etiopathogenesis, the present paper aims to shortly review the etiological, epidemiological and therapeutical assumptions on the topic, in particular the psychological-behavioral therapies. PATIENTS AND METHODS: The present study was carried out on 16 consecutive adult cancer patients affected by chemotherapy-induced anticipatory nausea and vomiting who had received at least four treatment cycles. All of them were submitted to induction of relaxation followed by hypnosis. RESULTS: In all subjects anticipatory nausea and vomiting disappeared, and major responses to chemotherapy-induced emesis control were recorded in almost all patients. CONCLUSIONS: The experience highlights the potential value of hypnosis in the management of anticipatory nausea and vomiting; furthermore, the susceptibility to anticipatory nausea and vomiting is discussed under the psychoanalytic point of view.

[Role of color Doppler ultrasonography with contrast media in the monitoring of hepatocarcinoma after intralesional treatment]. / Ruolo dell'eco color Doppler con mezzo di contrasto nel monitoraggio dell'epatocarcinoma dopo trattamento intralesionale.

INTRODUCTION: We investigated the accuracy of contrast-enhanced color Doppler US in the assessment of the effectiveness of intralesional treatment of hepatocarcinomas. MATERIAL AND METHODS: Eight cirrhotic patients (HCV+), Child-Pugh class B, with a single hepatocarcinoma (< 4 cm O) and ineligible for surgical resection for various reasons (age > 70 years, reduced partial hepatic reserve, esophageal varices at risk, postoperative recurrence, no consent to the operation) were submitted to radiohyperthermia (6 patients) and percutaneous alcoholization (2 patients). The diagnosis was made with alpha-fetoprotein titration. CT, B-mode and color Doppler US with the administration of Levovist (Schering AG, Berlin, Germany). Thirty and 60 days after the treatment, both the alpha-fetoprotein titration and contrast-enhanced color Doppler US were repeated. RESULTS: Baseline color Doppler was carried out before intralesional treatment in the 8 patients and was followed by Levovist color Doppler which showed some intralesional signals, afferent vessels and rich vascularization in all the lesions. At the first follow-up (30 days), no intralesional vascular signals or afferent vessels were detected in any patient, while rich peripheral vascularization persisted in all cases, even after radiofrequency and alcoholization treatments. At 60 days' follow-up, the color Doppler pattern of all cases was the same as at 30 days. CONCLUSIONS: The absence of any intralesional vascular signals in all the treated patients and the possible demonstration of complete tumor necrosis seem to confirm the important role of contrast-enhanced color Doppler US in monitoring focal hepatic lesions after intralesional treatment.

Differentiation, proliferation and apoptosis levels in human leiomyoma and leiomyosarcoma.

A comparative analysis of the differentiation pattern, the proliferative behaviour, and the level of apoptosis between human benign and malignant neoplasms of smooth-muscle (SM) tissue is lacking. The clinical, histopathological, immunochemical, and immunocytochemical features of leiomyomas (LM) and leiomyosarcomas (LMS) were investigated by a panel of monoclonal antibodies specific for some differentiation markers of SM tissue (SM myosin and alpha-actin, desmin, and SM22) and for markers of non-muscle tissue (vimentin and non-muscle myosin). Proliferating normal and neoplastic cells were identified by proliferating-cell nuclear antigen (PCNA)/Ki67 immunostainings and the apoptotic cells were revealed by means of the terminal-deoxynucleotidyltransferase-mediated dUTP nick-end labelling technique. Gel electrophoresis and Western blotting, performed with anti-(SM1/SM2 myosin isoform) antibody, indicated quantitative differences between LMS and LM, which mirrored higher positive to negative nuclear ratios for PCNA, Ki67 and apoptosis in malignant as opposed to benign neoplasms. With LM, however, a similar SM1 to SM2 ratio could be associated with different proliferation levels. Uterine, gastric and intestinal LMS displayed specific patterns of SM1/SM2 and/or non-muscle myosin expression that were not paralleled by different levels of proliferation/apoptosis. While the level of PCNA/Ki67 correlated with the level of apoptosis in normal SM tissues and LM, that of LMS did not. In vivo at the cellular level, LM and uterine LMS displayed a near-uniform SM tissue differentiation, whereas the other LMS displayed a lesser or a heterogeneous immunoreactivity. In vitro, cultured LMS cells showed a limited and peculiar expression of SM myosin. In conclusion, there is no reciprocal relationship between degree of differentiation and the level of proliferation, as exemplified by the finding that the less differentiated intestinal LMS displays the lowest proliferative behaviour and that the relatively more differentiated gastric LMS/metastasis is more proliferative.

Oestrogen-dependent expression of the SM2 smooth muscle-type myosin isoform in rabbit myometrium.

Ovarectomized rabbits displayed a decreased SM1 to SM2 ratio of smooth muscle-type myosin heavy chain isoforms compared to unoperated, virgin females which was reversed after 17beta-oestradiol administration to a value similar to that of control animals. When this steroid was given to sexually immature animals or to adult virgin rabbits, SM2 expression was not induced, as also happened with proliferating myometrial smooth muscle cells grown in vitro. In growing rabbit, the 17beta-oestradiol administration induced the formation of the circular and the longitudinal muscle layers, characteristics of sexually competent females. The SM2 isoform was up-regulated during postnatal development and the SM1 to SM2 ratio changed during pregnancy and post-partum period but not with human gonadotropin treatment which increases the level of circulating progesterone. Immunofluorescence staining of adult myometrium with anti-SM2 antibody indicated that this isoform is localized to the longitudinal layer exclusively and, in contrast to the circular layer, its expression was independent of oestrogen level. Difference in oestrogen sensitivity between the two layers was also detected for the expression of the intermediate filament protein vimentin and the thin filament protein calponin. Changes of SM2 expression in the myometrium correlated with variations in the oestrogen receptor density as also confirmed by decreased SM2 content/oestrogen receptor density in the circular layer when ovarectomized females were treated with the oestrogen antagonist ICI 182,780. Our results indicate that: (1) a specific distribution of myosin heavy chain exists within rabbit myometrium, and (2) SM2 myosin expression in this smooth muscle is under oestrogen control.

The impact of a psychological intervention on quality of life in non-metastatic breast cancer.

The aim of this study was to determine whether psychological intervention had a beneficial effect on the quality of life and behaviour of women diagnosed with breast cancer. 36 consecutive patients with non-metastatic breast cancer assigned to surgery and systemic chemotherapy were randomised to receive either psychological intervention (weekly cognitive individual psychotherapy and bimonthly family counselling) or standard follow-up. Personality (16-PF and IIQ), quality of life (FLIC), and depression (BDI) scores were the endpoints for this study, and the questionnaires were completed by the patients at diagnosis, and up to 9 months after diagnosis. Cognitive psychotherapy and family counselling improved both depression and quality of life indexes compared with the control group. Better emotional coping behaviours were also revealed by some changes in personality traits in the intervention group.

Carboplatin monochemotherapy in elderly patients with nonoperable transitional cell carcinoma of the bladder: a two-stage, phase II study.

Elderly patients with nonoperable transitional cell carcinoma of the bladder need a rather active, but less toxic treatment than full-dose polychemotherapy. This study was designed to determine whether the cisplatin-analogue carboplatin (which is less nephrotoxic and less neurotoxic than the parent compound) has sufficient activity against T2-T4 neoplasms (both nonmetastatic and metastatic) to warrant further development in phase III trials. Carboplatin dose was adjusted according to creatinine clearance, with a maximum dose of 300 mg/m2. The patient selection for this screening for activity was adjusted by the use of the 'optimal' two-stage design. Seventeen patients were enrolled, with a median age of 78 years (range: 70-85), a median performance status of 80% (range: 70-90%); 13 patients were lymph node-negative (10 T2, 2 T3, 1 T4) and 4 had locoregional or distant node metastases. Nine patients had a complete response (3 in the first, 9-patient, stage, and 6 in the second, 8-patient, stage), demonstrating that carboplatin had sufficient activity (at the 'desirable' target level of 35%); almost all responses were observed in T2 patients. Six patients had stable disease, and 2 had disease progression during treatment. The toxicity was acceptable, with only 41% of patients having grade II-III hematologic toxicity. More than 30% of patients were estimated to be free from progressive disease (54% alive) at 24 months. In our opinion carboplatin is suitable to be tested-in a phase III testing versus full-dose radiation therapy-as adjuvant after initial transurethral resection of the prostate in elderly patients with T2 transitional cell carcinoma of the bladder considered radically nonoperable for medical problems.

Expression of non-muscle myosin isoforms in rabbit myometrium is estrogen-dependent.

The putatative effects of different estrogen levels on the expression of non-muscle myosin isoforms in rabbit myometrium have been investigated using three monoclonal anti-platelet myosin heavy chain (MyHC) antibodies (NM-F6, NM-G2, and NM-A9). Western blotting analysis of proteolytic digests of human platelet actomyosin indicates that these antibodies are specific for three distinct epitopes. Comparative immunofluorescence tests on cultered human fibroblasts with polyclonal sequence-specific anti-MyHCA antibody suggest that the patterns of NM-F6, NM-.G2 and NM-A9, although similar, do not overlap with that of type-A MyHC. Distribution of NM myosin isoforms has been studied in indirect immunofluorescence assays using cryosections of tissues from rabbits at various stages of development, pregnancy, or from ovariectomized, 17beta-estradiol-treated ovariectomized, and human chorionic gonadotropin-treated animals. Non-muscle myosin antigenicity is still present in the myometrium when the female becomes sexually competent. The immunoreactivity of non-muscle myosin for NM-F6 is steroid-independent, since it does not change with pregnancy or ovariectomy, but that of NM-G2 is estrogen-dependent; the latter disappears during pregnancy and in ovariectomized animals treated with estradiol, whereas it is expressed in ovariectomized rabbits. Although non-muscle myosin immunoreactivity for NM-A9 is detectable under all the experimental conditions, it can assume different patterns of intracellular distribution in vitro (punctate vs filamentous), depending on culture conditions and the presence of estrogens.

The combination of mitomycin, vinblastine and cisplatin is active in the palliation of stage IIIB-IV non-small-cell lung cancer.

Twenty-eight patients with stage IIIB-IV non-small-cell lung cancer were treated with mitomycin C, vinblastine and cisplatin (MVP) in a phase II--minimax 2-stage design--randomized trial (with cisplatin plus etoposide as control arm). As indicated by the study design, the accrual was stopped after the 11th responder, and the combination was considered as active at the 40% level. Forty-six percent of patients had an improvement of their initial Karnofsky performance score, lasting a median of 24 weeks, and about 38% had a complete relief of symptoms. Hematologic toxicity was moderate to severe in about 50% of patients, and neurologic toxicity in about 18%; no grade 4 toxicity was observed. The estimated median progression-free survival was of 25 weeks. The observed activity and manageability, together with the positive effect on patient quality of life, account for a positive evaluation of MVP as a palliative treatment in advanced non-small-cell lung cancer.

In vitro differentiation of rhabdomyosarcomas induced by nickel or by Moloney murine sarcoma virus.

In vitro cultures and clonal derivatives have been established from rat rhabdomyosarcomas induced by Moloney-Murine Sarcoma Virus (MSV) or by nickel sulfide; differentiation ability has been studied as expression of desmin, embryonic and adult myosin isoforms, alpha-actin isoforms and cellular fusion. The two rhabdomyosarcoma models showed different levels of myogenic differentiation. Multinucleated myotube-like structures were frequently observed in cultures derived from nickel-induced tumours. Desmin was present in 50-80% of cells and embryonic myosin in up to 10%. In MSV-tumour-derived cultures and in their metastases or clonal derivatives two cell types are present in different ratios: spindle-shaped cells, adherent to plastic surfaces, and rounded cells, loosely attached or floating free in the medium. These cultures showed features of myogenic differentiation (10-80% desmin-positive cells), but embryonic myosin expression and production of multinucleated myotube-like structures were very rare events. Cultures from autochthonous lymph node and lung metastatic cells showed similar patterns of differentiation. Retinoic acid increased differentiated features (myotube formation and embryonic myosin expression) only in nickel-induced rhabdomyosarcoma cells. The two models described here mimic the heterogeneity in differentiation pattern found among human rhabdomyosarcomas. Myogenic differentiation ability was retained at a good level by nickel-induced tumours, whereas it was strongly impaired in MSV-induced tumours.

Neonatal myosin heavy chains are not expressed in Ni-induced rat rhabdomyosarcoma.

Myosin heavy chain (MHC) composition of chemically-induced rhabdomyosarcoma (RMS) was analyzed by gel electrophoresis and Western blotting using a panel of monoclonal antimyosin antibodies specific for embryonic-, neonatal-, slow- and adult fast-type MHC isoforms. Myosin extracted from tumours and electrophoresed on 6%-sodium dodecyl sulfate (SDS)glycerol gels was found to migrate as three distinct MHC components. These polypeptides were present in different relative amounts in the five RMS studied. Western blotting experiments revealed that variable proportions of embryonic-, slow- and adult fast-, but not neonatal-type, MHC isoforms are consistently expressed in RMS. Indirect and double immunofluorescence procedures applied to cryosections of tumoral tissue showed that: (a) RMS cells were unreactive with antineonatal-type-MHC antibody, (b) the majority of neoplastic, desmin-positive, cells contained embryonic- as well as adult fast-type MHCs and (c) a minority of cells were labelled by anti-slow MHC antibody. The results of this study indicate that there is no obligatory sequence of MHC isoform expression in the molecular transition (emb----neo----adult) which occurs during rat skeletal myogenesis.

Myosin isoform expression in rat rhabdomyosarcoma induced by Moloney murine sarcoma virus.

Myosin isoform expression was analyzed in experimental rhabdomyosarcoma (RMS) using monoclonal antibodies (mAbs) and immunofluorescence techniques. Tumors induced by inoculating newborn rats with Moloney murine sarcoma virus (Mo-MSV) were examined 30-90 days after birth. Nine tumors and two lymph node metastases were studied by direct, indirect, and double immunofluorescence assays using a panel of five anti-myosin mAbs. The mAb BF-45 was specifically reactive with embryonic myosin heavy chain (MHC), mAb BF-34 was specific for a neonatal MHC epitope, mAb BF-B6 was directed against an epitope present in both embryonic and neonatal MHC, and mAbs BF-F3 and BF-32 detected epitopes present in adult MHC isoforms. Anti-desmin antibodies were also used for comparison. The results of this study show that: (1) the majority of neoplastic cells stained for desmin while only a minority of neoplastic cells were labeled by anti-myosin antibodies; (2) myosin positive tumor cells contained predominantly embryonic and neonatal MHC types but rare RMS cells reacted exclusively with anti-adult myosin antibodies; and (3) adult and embryonic MHC phenotypes were occasionally detected within the same tumor cell especially in RMS with the longest latencies. Together these results would suggest that the mechanism(s) regulating MHC gene expression in skeletal muscle cells can be altered by the transforming activity of Mo-MSV.