A hair matrix
tumor showing an unusual
tumor cell arrangement was found at the base of a solitary trichoepithelioma. Coexisting with solid epithelial islands and immature hair follicle-like stroma resembling the Verocay bodies of
neurilemmoma or "ripplemarks" on waves were found. In other areas myxomatous degeneration of the stroma changed the rippling into a cribriform pattern. In some parts of the
tumor there was a dense
melanin pigment associated with MEL5 stained melanocytes. S-100 and CD1 (OKT6)
antigen stains demonstrated Langerhans cells scattered in the parenchyma and less frequently in the stroma. The majority of
tumor cells were considered immature pilar cortical cells because of the following: 1. HKN-6 was strongly positive; 2. a large number of melanocytes were associated with
tumor cells in some foci; 3. ultrastructurally immature
tumor cells, which had electron-dense tonofilaments and many desmosomes, were transformed without production of
trichohyalin granules into semikeratinized cells which showed nuclear degeneration and loss of electron density in tonofilaments. This
tumor, however, has not attained the degree of differentiation observed in trichoblastoma (1) another example of an immature cortical cell
tumor. Squamous eddy-like or horn pearl-like foci of incomplete keratinization and large
keratin-filled
cysts were also present within the immature parenchyma, indicating that some immature cells were differentiating toward non-cortical cells, as found in the outer sheath. We would like to designate this
tumor "rippled pattern trichomatricoma", a new entity.