NDT80, a meiosis-specific gene required for exit from pachytene in Saccharomyces cerevisiae.

We describe the identification of a new meiosis-specific gene of Saccharomyces cerevisiae, NDT80. The ndt80 null and point mutants arrest at the pachytene stage of meiosis, with homologs connected by full-length synaptonemal complexes and spindle pole bodies duplicated but unseparated. Meiotic recombination in an ndt80 delta mutant is relatively normal, although commitment to heteroallelic recombination is elevated two- to threefold and crossing over is decreased twofold compared with those of the wild type. ndt80 arrest is not alleviated by mutations in early recombination genes, e.g., SPO11 or RAD50, and thus cannot be attributed to an intermediate block in prophase chromosome metabolism like that observed in several other mutants. The ndt80 mutant phenotype during meiosis most closely resembles that of a cdc28 mutant, which contains a thermolabile p34, the catalytic subunit of maturation-promoting factor. Cloning and molecular analysis reveal that the NDT80 gene maps on the right arm of chromosome VIII between EPT1 and a Phe-tRNA gene, encodes a 627-amino-acid protein which exhibits no significant homology to other known proteins, and is transcribed specifically during middle meiotic prophase. The NDT80 gene product could be a component of the cell cycle regulatory machinery involved in the transition out of pachytene, a participant in an unknown aspect of meiosis sensed by a pachytene checkpoint, or a SPO11- and RAD50-independent component of meiotic chromosomes that is the target of cell cycle signaling.

Oral tongue cancer in patients less than 45 years old: institutional experience and comparison with older patients.

PURPOSE: To evaluate the demographics, differential risk profile, and treatment outcome in patients with squamous cell carcinomas (SCCs) of the oral tongue according to age at diagnosis. PATIENTS AND METHODS: Patients with invasive SCC of the oral tongue who presented during the years 1985 to 1996 were identified using institutional tumor registry data. Demographics and clinical and pathologic characteristics were abstracted from the medical charts. RESULTS: Eighty-eight patients were identified; 87 were included for analysis. Thirty patients were diagnosed at < or = 45 years of age and 57 at > or = 46 years. The groups showed comparable American Joint Committee on Cancer (AJCC) staging and male predominance. Prior exposure to tobacco and/or alcohol was noted in 40% and 82% of younger and older patients, respectively (P < .001); multiple smoking-related cancers occurred only in older patients (24.5% of older patients, P < .001). With median follow-up time of 29 months (younger group) and 21 months (older group), there were no significant differences in relapse rates, cancer-free survival (CFS), and overall survival (OS) rates (actuarial 5-year CFS rate, 48% and 54% in the younger and older patients, respectively; P = .91). Grouping patients according to smoking and/or alcohol history showed a trend toward better CFS in those with prior exposure to tobacco or alcohol compared with those with neither (5-year CFS rate, 60% and 38%, respectively, P = .11). In a multivariate analysis of all patients, with age used as a continuous parameter, only stage predicted CFS (P = .0019); for patients treated surgically with curative intent, only risk group predicted CFS (P = .0369). CONCLUSION: Prognosis of oral tongue SCC was not affected by age at diagnosis. CFS rates tended to be worse in cases not related to prior tobacco or alcohol exposure. Multiple smoking-related cancers occurred only in older patients.

Critical values in hematology.

INTRODUCTION: Critical values are life-threatening results that require immediate notification to the patient's healthcare provider. Accreditation bodies require laboratories to establish critical values. A survey of Ontario laboratories was conducted to determine current practice for critical values in hematology. METHODS: The survey was sent to 182 participants questioning sources for establishing critical values, levels, review frequency, delta checks, and reporting. The survey was completed by laboratory managers, supervisors, technical specialists, senior technologists, and bench technologists working in hematology. RESULTS: The majority of participating laboratories have established critical values limits for hemoglobin, leukocyte counts, and platelet counts. Most laboratories also include the presence of malaria parasites and blast cells. Some laboratories reported the presence of plasma cells, sickle cells, schistocytes, and spherocytes as critical values. Multiple sources are used for establishing a critical value policy. There was variability for the frequency of critical values review. Rules may differ for a first-time patient sample vs. a repeat patient sample. Delta checks are seldom used to determine whether a result should be called a critical value. Most participants require the individual taking the critical result(s) to read back and confirm that they are directly involved with the patient's care. CONCLUSION: There is a lack of consensus for critical values reporting in hematology. As critical value reporting is crucial for patient safety, standardization of this practice would be beneficial.

Internal Quality Control Practices in Coagulation Laboratories: recommendations based on a patterns-of-practice survey.

INTRODUCTION: Internal quality control (IQC) procedures are crucial for ensuring accurate patient test results. The IQMH Centre for Proficiency Testing conducted a web-based survey to gather information on the current IQC practices in coagulation testing. METHODS: A questionnaire was distributed to 174 Ontario laboratories licensed to perform prothrombin time (PT) and activated partial thromboplastin time (APTT). RESULTS: All laboratories reported using two levels of commercial QC (CQC); 12% incorporate pooled patient plasma into their IQC program; >68% run CQC at the beginning of each shift; 56% following maintenance, with reagent changes, during a shift, or with every repeat sample; 6% only run CQC at the beginning of the day and 25% when the instruments have been idle for a defined period of time. IQC run frequency was determined by manufacturer recommendations (71%) but also influenced by the stability of test (27%), clinical impact of an incorrect test result (25%), and sample's batch number (10%). IQC was monitored using preset limits based on standard deviation (66%), precision goals (46%), or allowable performance limits (36%). 95% use multirules. Failure actions include repeating the IQC (90%) and reporting patient results; if repeat passes, 42% perform repeat analysis of all patient samples from last acceptable IQC. CONCLUSION: Variability exists in coagulation IQC practices among Ontario clinical laboratories. The recommendations presented here would be useful in encouraging standardized IQC practices.

MYC gene amplification in double minute chromosomes in an aggressive large B-cell lymphoma with leukemic presentation: a case report.

Double-minute chromosomes (dmin) are small chromatin particles that lack a centromere. They represent extrachromosomal form of gene amplification. Dmin are very rarely encountered in lymphoid neoplasms. We describe a case of a leukemic presentation of large B-cell lymphoma with dmin. Fluorescence in situ hybridization analysis identified these dmin as comprising MYC genes.

Temporal comparison of recombination and synaptonemal complex formation during meiosis in S. cerevisiae.

In synchronous cultures of S. cerevisiae undergoing meiosis, an early event in the meiotic recombination pathway, site-specific double strand breaks (DSBs), occurs early in prophase, in some instances well before tripartite synaptonemal complex (SC) begins to form. This observation, together with previous results, supports the view that events involving DSBs are required for SC formation. We discuss the possibility that the mitotic pathway for recombinational repair of DSBs served as the primordial mechanism for connecting homologous chromosomes during the evolution of meiosis. DSBs disappear during the period when tripartite SC structure is forming and elongating (zygotene); presumably, they are converted to another type of recombination intermediate. Neither DSBs nor mature recombinant molecules are present when SCs are full length (pachytene). Mature reciprocally recombinant molecules arise at the end of or just after pachytene. We suggest that the SC might coordinate recombinant maturation with other events of meiosis.

Analysis of wild-type and rad50 mutants of yeast suggests an intimate relationship between meiotic chromosome synapsis and recombination.

The RAD50 gene of S. cerevisiae is required during meiosis for both recombination and chromosome synapsis and is also required for repair of double strand breaks during vegetative growth. We present below the isolation and analysis of several types of rad50 mutants. We show that null mutations block both meiotic recombination and formation of synaptonemal complex (SC) at early stages, while nonnull mutations block both processes at intermediate stages. These observations suggest that recombination and SC formation involve a series of intimately related events. Furthermore, all rad50 mutants block formation of tripartite SC structure but permit other aspects of SC development, i.e., formation of axial cores. In light of this and other observations, the meiotic and mitotic defects of rad50 mutants can be accounted for economically by the proposal that meiotic recombination, meiotic chromosome pairing, and vegetative DNA repair all use a common chromosomal homology search that involves RAD50 function.

Relapse of acute myelogenous leukemia presenting as acute otitis externa. A case report.

The association of leukemia with auditory complications is an obscure, though an important one, especially from the therapeutic point of view. A case is presented of a relapse of acute myelogenous leukemia presenting as an acute otitis externa. The leukemic infiltrates in the external auditory canal are demonstrated by both light and electron microscopy. The otologic lesions in leukemias are reviewed and the importance of early diagnosis is emphasized, since the aural involvement may precede the clinical relapse of the leukemia, as in the current case. The value of computerized axial tomography of the ear and of tissue biopsy for diagnosis is stressed. The recognition of the presence of leukemic infiltrates in the ear causing otologic symptoms allows for the prompt institution of appropriate therapy.

Primary extraosseous cemento-ossifying fibroma of the auricle.

BACKGROUND: A mass of the auricle is uncommon. An enlarging lesion may be the result of a reactive process, or a benign or malignant neoplasm. The literature is reviewed, and a case of extraosseous cemento-ossifying fibroma of the auricle is presented. METHODS: A 22-year-old white man presented with a 3-month history of an enlarging 2 cm mass in the right concha cavum. An incisional biopsy demonstrated cemento-ossifying fibroma. The lesion was resected en bloc, and the patient did well. There is no evidence of recurrence. RESULTS: Pathological examination of the excised mass revealed a well-circumscribed but unencapsulated spindle cell lesion with foci of osteoid and cementum deposition. It did not involve the auricular cartilage, and there was no connection with the overlying epidermis. CONCLUSIONS: This is a case report of an extraosseous cemento-ossifying fibroma of the auricle. This benign tumor should be completely excised because local recurrence may otherwise result.

Microinvasive breast carcinoma: clinicopathologic analysis of a single institution experience.

BACKGROUND: Microinvasive breast carcinoma (MIC) has a good prognosis but specific definitions have varied in the past, making the clinical significance of MIC a subject of debate. METHODS: Microscopic slides of 59 cases of breast carcinoma originally diagnosed as MIC were reviewed retrospectively. Histologic parameters were correlated with clinical findings and outcome to define diagnostic criteria better. RESULTS: On review, the 59 cases were recategorized as follows: pure DCIS (N = 16), DCIS with foci equivocal for microinvasion (N = 7), DCIS with > or =1 focus of microinvasion (N = 11), T1 invasive carcinomas with > or =90% DCIS (N = 18), and T1 tumors with <90% DCIS (N = 7). The MIC cases in the current study averaged 3 separate foci of early infiltration outside the basement membrane, each one not >1.0 mm. The mean follow-up was 95 months. Six patients (10%) had only local recurrence: 1 case each in patients with equivocal microinvasion, microinvasion, and T1 tumors with <90% DCIS and 3 cases among the patients with T1 tumors with > or = 90% DCIS. Four patients, all with T1 tumors with > or =90% DCIS, had distant failure (7%). In the MIC group, only one patient developed a local recurrence after breast conservation. No patient had axillary lymph node metastasis. For the entire series, factors associated with local recurrence were younger age, breast conservation versus mastectomy, and close surgical margins. The only factor associated with distant failure was the size of the DCIS component. Seven patients with T1 tumors with > or =90% DCIS experienced local or distant failure and 5 of these (71%) developed progressive disease or died of disease. All other patients who developed a recurrence were disease free at last follow-up. In a retrospective series, poorer outcome in carcinomas with > or =90% DCIS may be related to the greater likelihood of missed larger areas of invasive carcinoma. Therefore, meticulous and extensive sampling of these carcinomas is required. CONCLUSIONS: MIC as defined has a good prognosis. It has a different biology than T1 invasive carcinoma with > or =90% DCIS, which may progress and cause death. Large tumors with multiple foci of microinvasion may have metastatic potential.

Primary combined malignant melanoma and ductal carcinoma of the breast. A report of two cases.

BACKGROUND: Tumors consisting of a combination of malignant melanoma and carcinoma are very rare. The authors report two such cases occurring as primary breast tumors. METHODS: The breast tumors were analyzed by histologic, immunohistochemical, and ultrastructural techniques. RESULTS: Histologically, the tumors were composed of a closely related admixture of ductal adenocarcinoma and malignant melanoma with abundant melanin pigment. Ductal carcinoma in situ was identified in both cases, confirming their origin in the breast. In both tumors, double-labeling immunohistochemistry showed that the epithelial component was immunoreactive for cytokeratin, the melanoma component was immunoreactive for HMB45, and both components were immunoreactive for S-100 protein. Immunostains for estrogen and progesterone receptors were negative in both tumors. Electron microscopy demonstrated glandular lumens and junctional complexes in the epithelial component and melanosomes and premelanosomes in the melanoma component. In one of the cases, rare tumor cells contained both premelanosomes and desmosomes. CONCLUSIONS: Combined malignant melanoma and carcinoma is a rare tumor. Only a handful of cases have been reported. The authors report two such cases occurring as primary tumors of the breast. The histology of the tumors revealed a closely related admixture of pigmented malignant melanoma and ductal carcinoma. Double-labeling immunohistochemistry showed that cytokeratin and HMB45 were expressed in the tumors, but not within the same cells. The authors propose describing this type of lesion as a single tumor of breast origin with bidirectional differentiation.