Aims-To assess the consistency and reproducibility of assessment of c-erbB-2 immunostaining, and to examine some of the problems relating to inter-and intraobserver variability in the documentation of positive staining; to profile the spectrum of cytoplasmic and membranous staining in a wide range of tumour types. Methods-A total of 283 neoplasms were examined for immunohistochemical expression of the c-erbB-2 oncoprotein. Three independent observers were required to assess intensity both of membrane and cytoplasmic staining on a three point and then a four point scale. Extent of positive staining was also assessed on a two point scale. A minimum of two weeks elapsed between assessments using the differing scales.

An 82-year-old male presented with a two-month history of hoarseness. A 2 cm pedunculated lesion was removed from the base of his epiglottis. Microscopy showed a polypoid atypical spindle cell lesion. Multiple levels failed to reveal an invasive squamous cell carcinoma. On the basis of haematozylin and eosin stained sections the main differential diagnosis was a pseudosarcoma with an overlying dysplastic squamous mucosa or infiltrating spindle cell carcinoma. Immunohistochemistry showed positive staining for vimentin but no convincing staining with antibodies to cytokeratin and EMA. Ultrastructural analysis also failed to reveal epithelial characteristics. Ploidy analysis by static cytophotometry of the spindle cell proliferation revealed an aneuploid stem line with a DNA index of 1.67. On the basis of this the process was felt unlikely to be reactive and a diagnosis of a spindle cell squamous carcinoma was made. This diagnosis was subsequently supported by a clinical recurrence of the nodule at a six-month follow-up.

This study documents the reactions of the monoclonal antibody KP-1, which detects histiocytes in paraffin sections, with 137 sarcomas, 48 lymphomas, 28 carcinomas, 7 malignant melanomas and 8 cystosarcoma phyllodes. The soft tissue sarcomas had been previously immunophenotyped. Positive staining was obtained in all categories of sarcoma except clear-cell sarcomas. Most categories of sarcoma showed staining in less than 10% of tumour cells although a minority of leiomyosarcomas showed more extensive staining. Five of 7 malignant melanomas were also positive while all lymphomas and carcinomas were negative. We conclude that KP-1 positivity is not helpful in supporting the histiocytic origin of a tumour and is of limited value in the differential diagnosis of soft tissue sarcomas or their separation from other categories of malignancy.

Clear cell carcinoma of salivary gland is a rare neoplasm. We report a third case of clear cell carcinoma arising in a pleomorphic adenoma and also in an extraparotid location. We document the immunohistochemical profile of the tumour including reactivity with a marker for the c-erbh-2 oncoprotein and suggest a myoepithelial origin for these lesions. The presence of a tetraploid stemline may account for the rapid tumour progression in this case.

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