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S-100 immunoreactivity in primary and metastatic carcinoma of the breast: a potential source of error in immunodiagnosis.

Immunoreactivity for S-100 protein, typically a marker for malignant melanoma and neural-derived tumors, was observed in neoplastic cells of 57 of 68 cases (84%) of formalin-fixed, paraffin-embedded primary and/or metastatic carcinoma of the breast of various histologic types. The extent of S-100 immunoreactivity varied, with only a minor proportion of positive tumor cells noted in some cases. An awareness of this staining profile for S-100 protein, particularly in metastatic poorly differentiated neoplasms with unknown primaries, is imperative for accurate immunohistochemical interpretation. Using a panel of reagents which includes antibodies to keratin proteins and epithelial membrane antigen, the epithelial nature of S-100-positive carcinomas may be readily defined. Tumor cells in all cases of primary and metastatic carcinoma of the breast evaluated in this study exhibited strong staining for both of these tissue markers. To preclude misinterpretation of tumor type due to anomalous staining patterns for a specific antibody, eg, S-100 protein, a panel of antibodies is recommended for assessment of metastatic poorly differentiated tumors.

Breast Neoplasms↗

Absorption of free and antibody-conjugated horseradish peroxidase to fixed glial cells in tissue culture, a possible source of error in immunohistochemistry.

Incubation of cellular preparations with antibody-conjugated peroxidase result in a very strong unspecific staining, for one electropolar binding of the basic enzymic protein with the cell structures. In immunohistochemical practice, it may represent an evil as import as when dealing with immunofluorescence techniques. This background can to a great extent be avoided by rinsing the preparations in buffer at pH = 6.2.

Absorption↗

Plasma lipids and mortality: a source of error.

Cause-specific mortality-rates were calculated in 17 718 men aged 40-64 years who participated in the Whitehall Study. Over a 7 1/2 year follow-up, total mortality showed a J-shaped relation to the plasma cholesterol concentration measured at entry to study. This shape resulted from a strong positive relation of plasma cholesterol with deaths from coronary heart-disease (CHD) combined with an opposite (inverse) relation between plasma cholesterol and deaths from other causes. Cancer mortality was 66% higher in the group with the lowest plasma cholesterol than in the group with the highest plasma cholesterol. Further analysis showed that this inverse association between plasma cholesterol and non-CHD deaths was confined to the first 2 years of follow-up; beyond this time total mortality and cholesterol level were evenly and positively correlated. Analysis of data from the Framingham study revealed the same phenomenon, which is presumed to result from the metabolic consequences of cancer which was present but unsuspected at the time of examination.

Adult↗