A quality control program for mutation detection in KIT and PDGFRA in gastrointestinal stromal tumours

Background

Although most gastrointestinal stromal tumours (GIST) carry oncogenic mutations in KIT exons 9, 11, 13 and 17, or in platelet-derived growth factor receptor alpha (PDGFRA) exons 12, 14 and 18, around 10% of GIST are free of these mutations. Genotyping and accurate detection of KIT/PDGFRA mutations in GIST are becoming increasingly useful for clinicians in the management of the disease.

Method

To evaluate and improve laboratory practice in GIST mutation detection, we developed a mutational screening quality control program. Eleven laboratories were enrolled in this program and 50 DNA samples were analysed, each of them by four different laboratories, giving 200 mutational reports.

Results

In total, eight mutations were not detected by at least one laboratory. One false positive result was reported in one sample. Thus, the mean global rate of error with clinical implication based on 200 reports was 4.5%. Concerning specific polymorphisms detection, the rate varied from 0 to 100%, depending on the laboratory. The way mutations were reported was very heterogeneous, and some errors were detected.

Conclusion

This study demonstrated that such a program was necessary for laboratories to improve the quality of the analysis, because an error rate of 4.5% may have clinical consequences for the patient.     

Bone loss in hypothyroidism with hormone replacement. A histomorphometric study

To determine the influences of hormone replacement on bone tissue in primary hypothyroidism, a histomorphometric study on undecalcified transiliac bone specimens was performed before treatment in ten patients, during the first month of treatment in 16 patients, and after more than six months of treatment in 15 patients. There were no obvious clinical or biologic signs of excessive replacement therapy. Before treatment, trabecular resorption surfaces were lower and bone cortical thickness was increased. From as early as the first month of treatment, trabecular resorption surfaces and cortical porosity were higher than normal but cortical thickness was still increased. After more than six months of treatment there was a significant loss of trabecular (decreased trabecular bone volume) and cortical (normal mean cortical width; increased porosity) bone with hyperremodeling (increased trabecular resorption surfaces and trabecular osteoid surfaces). This osteoporosis is similar to that observed in hyperthyroidism.     

Watch and Wait Approach for Re-excision After Unplanned Yet Macroscopically Complete Excision of Extremity and Superficial Truncal Soft Tissue Sarcoma is Safe and Does Not Affect Metastatic Risk or Amputation Rate

Annals of Surgical Oncology - The benefits of systematic re-excision (RE) after initial unplanned excision (UE) of soft tissue sarcoma (STS) are unknown. The aim of this study was to evaluate the...     

Metastasizing fibrous histiocytoma of the skin: a clinicopathologic and immunohistochemical analysis of three cases.

The clinicopathologic and immunohistochemical features of three metastasizing fibrous histiocytomas of the skin are presented. The first patient had a 1.3-cm nodule in the right thigh, with right inguinal lymph node metastases 19 years later. The second patient, who had a 3-cm nodule excised from his left thigh and inguinal lymph node metastasis after 4 months, had a favorable outcome 14 years after local radiotherapy and chemotherapy. The third had a 2-cm nodule in his neck, which recurred 16 months later. Four months later, cervical lymph node metastases were found. The patient was alive and well 26 months after initial surgery. All three primary skin tumors involved the dermis and subcutis, appeared well-delineated but nonencapsulated, were associated with some degree of epidermal hyperplasia, and showed features of aneurysmal/atypical or cellular fibrous histiocytoma. The number of mitoses ranged from 6 to 11 per 10 high-power fields. Recurrences and metastases showed morphologic features similar to primary lesions. Tumor cells were positive, at least focally, for CD 68, Ki-M1p, and Factor XIIIa, and occasionally for smooth muscle actin. Desmin, CD 34, S-100 protein, and cytokeratin stainings were negative. Primary neoplasms, recurrences, and metastases showed a Mib-1 labeling index of 10% or less. Cellular, aneurysmal, and atypical (pseudosarcomatous) fibrous histiocytomas of the skin can metastasize, yet they often show a protracted clinical course. Risk factors for metastatic dissemination include large size, high cellularity, aneurysmal changes, marked cellular pleomorphism, high mitotic activity, tumor necrosis, and repeated local recurrences.     

Micrometastases to axillary lymph nodes from carcinoma of breast: detection by immunohistochemistry and prognostic significance

Metastases to axillary lymph nodes is an important factor in predicting prognosis and survival in primary operable carcinoma of the breast. A series of post mastectomy lymph nodes (150 cases) was selected in this retrospective study, in which the initial diagnosis had been no metastases by light microscopy and in which a long follow-up was available (average 10 years). The original H&E sections from these cases were immunostained to detect metastases which might not have been previously appreciated. The study was performed using a cocktail of 5 monoclonal antibodies directed against epithelial antigens. The object was to explore the possibility of detection of occult micrometastases by immunohistochemistry and to evaluate their prognostic significance. Micrometastases with individual cells and cell clusters were readily detected by this technique in 14% of all cases. It also became apparent towards the end of the study that micrometastases could be detected with equal sensitivity by any one of the 5 monoclonal antibodies. Positive staining of malignant cells was found to be more frequent in invasive lobular carcinoma (ILC) than in invasive ductal carcinoma (IDC). However, for the IDC group a striking association was found between micrometastases and both recurrence and survival rate. The ILC sample was considered too small for meaningful interpretation. We recommend the use of immunohistochemical techniques using monoclonal antibodies for the detection of occult metastases in lymph nodes to improve the prediction of recurrence and survival in invasive ductal carcinoma of the breast.