Rippled‐pattern trichomatricoma

The document described a unique hair matrix tumor, termed "rippled pattern trichomatricoma," found at the base of a trichoepithelioma. This tumor exhibited an unusual arrangement of tumor cells, with alternating epithelial cords and stroma resembling Verocay bodies or wave ripple marks. Some areas showed myxomatous degeneration, creating a cribriform pattern, and dense melanin pigment was present with MEL5 stained melanocytes. Langerhans cells were identified using S-100 and GDI antigen stains. The majority of tumor cells were considered immature pilar cortical cells, indicated by strong HKN-6 positivity, association with melanocytes, and ultrastructural features. The tumor showed incomplete differentiation compared to trichoblastoma, with some cells differentiating toward non-cortical cells, forming squamous eddy-like foci and keratin-filled cysts.