Generalized trichoepitheliomas with alopecia and myasthenia gravis: clinicopathologic and immunohistochemical study and comparison with classic and desmoplastic trichoepithelioma.

We report on a patient with a syndrome characterized by smooth facial papules and nodules; alopecia of the eyebrows, eyelashes, and most body hair; mild alopecia of scalp hair; possibly hypohidrosis; and myasthenia gravis. The clinical, histologic, and immunohistochemical findings are compared with classic and desmoplastic trichoepitheliomas. All fourteen biopsy specimens of the patient showed a lacelike network of basaloid cells with follicular differentiation and a prominent stroma with focal alkaline phosphatase activity, as in fourteen comparison specimens of classic trichoepithelioma. Studies with antikeratin antibodies of various specificities also revealed similar patterns. The tumor cells showed a keratin phenotype characteristic of cells of the infrainfundibular outer root sheath, that is, positive staining with basal keratinocyte markers, negative staining with suprabasal keratinocyte markers, and patchy staining with LP2K (against keratin 19). beta 2-Microglobulin expression was partially or totally absent. It is concluded that the lesions in our patient actually are trichoepitheliomas. The condition may represent a new syndrome that either is closely related to the generalized hair follicle hamartoma (basaloid follicular hamartoma) or is a variant. The finding of generalized trichoepitheliomas with clinical and microscopic alopecia should alert one to the possibility of myasthenia gravis.