Sialomucin in Paget cells of extramammary Paget's disease

Role of mucins in the skin during benign and malignant conditions

Skin-related diseases comprise a major health challenge to the practicing physician, and constitute a significant psychological, social and financial burden to the society. Further, skin cancer, especially non-melanoma skin cancer is currently the leading type of malignancy in the Western world. Given the huge burden of skin diseases, there is growing emphasis on understanding their pathophysiology, and towards their early detection. Mucins are high-molecular weight O- and N-linked glycoproteins that have emerged in recent years as important molecules in maintaining health and in promoting or protecting against inflammation and cancer. They have also begun to emerge as highly specific diagnostic and prognostic markers and novel therapeutic targets in several malignant disorders. However, their role in cutaneous pathologies has remained largely obscured. The present review provides the expression patterns and proposed role of mucins in the healthy skin and various benign and malignant skin diseases. The review has immense clinical significance as the availability of highly specific reagents including monoclonal antibodies against mucins makes them extremely attractive targets for specific diagnosis and/or immunotherapy of benign and malignant cutaneous diseases.

Mucin immunohistochemistry in the diagnosis and mapping of extramammary Paget's disease

Extramammary Paget's disease (EMPD) is a rare skin cancer of the genital region in which cancer cells with enlarged nuclei and pale cytoplasm are scattered singly in the affected epidermis. These cancer cells, called Paget cells, contain mucin, which is never found in normal epidermis. The oligosaccharide side chains of Paget cell mucin end with sialic acid. Sialic acid is easily detected by zirconyl haematoxylin or alcian blue. The other sugars in the oligosaccharide chains can be detected by the periodic acid-Shiff reaction. Rarely, the diagnosis of EMPD is complicated by the absence of mucin from the Paget cells. We have examined such an atypical case. The oligosaccharide side chains, including the sialic acids, are absent. In both this case and a typical case, the Paget cells contain epithelial membrane antigen mucin (MUC1) core protein and usually contain gastric surface-type mucin (MUC5AC) core protein, which can be stained by antibodies. Since neither core protein is found in normal epidermis, epithelial membrane antigen core protein may be the most reliable diagnostic marker for extramammary Paget's disease. In both the atypical case and the typical case of Paget's disease, some cells that look like keratinocytes contain mucin core proteins. These may be incipient Paget cells. We suggest that using th epithelial membrane antigen core protein as a marker for the true extent of extramammary Paget's disease could facilitate complete excision and reduce the rate of recurrence.

Zirconyl hematoxylin vs. alcian blue staining in a case of extramammary Paget's disease

BACKGROUND

Despite its occasional unavailability, alcian blue has long been the stain of choice for the pathognomonic mucin-secreting cells of extramammary Paget's disease. Zirconyl hematoxylin is a recently developed substitute for alcian blue, which is made from common laboratory materials.

METHODS

We have stained sections from three different areas of the same case of extramammary Paget's disease with zirconyl hematoxylin, destained in 7% HCl in ethanol, restained with alcian blue at pH 2.5, destained in 2.5% trifluoroacetic acid in dichloromethane, and restained with zirconyl hematoxylin.

RESULTS

Each staining procedure stained the same cells.

CONCLUSIONS

Zirconyl hematoxylin is a useful alternative to alcian blue in the diagnosis of extramammary Paget's disease.

Histochemical analysis of sialomucin in Paget cells of mammary and extramammary Paget's disease

The cytoplasmic sialomucin in Paget cells of both mammary and extramammary Paget's diseases was examined, using a new method proposed by Volz et al. (1987a, b). The staining methods used involved an electrolyte-Alcian Blue (pH = 5.8) and periodic acid Schiff. Oxidation was performed with 0.4 mmol/l periodate in 1 mol/l HCl at 4 degrees C or 50 mmol/l periodate in distilled water at room temperature for 1 h. Methylation, saponification, borohydride reduction, and digestion with diastase, neuraminidase (Vibrio cholerae) or chondroitinase ABC, were also employed. The cytoplasmic mucin was found to exhibit positive reaction for the above staining which were variously altered by the chemical modification procedures and diminished in intensity or abolished by digestion with neuraminidase. These results suggest that the cytoplasmic mucin in Paget cells is sialomucin without side-chain substituent in genital Paget's disease, and that with a substituent at C7 in mammary Paget's disease.

Extramammary Paget's disease: an annotated review

The incidence, clinical features, histogenesis, and treatment of extramammary Paget's disease (EMPD) are reviewed. This unusual skin lesion is associated with an underlying adnexal neoplasm in about 50% of cases. Also, the incidence of distant organ malignancies of EMPD is higher than expected by chance. Even in the absence of a recognizable underlying cancer, EMPD may occasionally produce distant metastases, indicating the malignant potential of this condition. Histochemical, immunohistological, and lectin binding studies demonstrate that the cell of origin of EMPD is the exocrine cell of sweat glands. Although EMPD may arise from eccrine cells, derivation from apocrine cells appears more common. The treatment of the primary lesion, by wide margin excision, is fraught by a high recurrence rate. Chemosurgery may reduce local relapse of EMPD. The value of adjuvant radiation therapy is unestablished. Chemotherapy has induced remission in 2 cases of advanced EMPD and needs testing in clinical trials.