Non-erythroid spectrin (fodrin) in cutaneous tumours: diminished in cell membranes, increased in the cytoplasm.

The expression and distribution of non-erythroid spectrin (alpha-fodrin), a basic protein of the cell membrane skeleton, was investigated by immunohistochemical methods in 42 cutaneous tumours. The suprabasal keratinocytes of the normal epidermis showed plasma membrane-associated spectrin. The basal cells of the normal epidermis, seborrhoeic keratosis, and basal cell carcinoma, revealed both intracytoplasmic and membrane-bound spectrin. In squamous cell carcinoma, the expression of spectrin was heterogeneous and mostly intracytoplasmic. The dysplastic cells of solar keratosis expressed no spectrin at all. In various types of melanocytic naevi, intracytoplasmic and discontinuous membrane-bound spectrin was found in most tumour cells. Malignant melanomas showed a heterogeneous intracytoplasmic staining for spectrin, or were negative. The results indicate a diminished amount, or a total lack, of membrane-bound spectrin with increasing depolarization and proliferation of cells in solar keratosis and pigment cell tumours, but a partial preservation in polarized cells of basal cell carcinoma. The increase and heterogeneity, in cytoplasmic spectrin, of squamous cell carcinoma and malignant melanoma seemed to be associated with the less differentiated, invasive cells of these malignant tumours.