Giant trichoblastoma mimicking malignancy

We report a case of giant trichoblastoma, a rare benign hair germ tumor. A 73-year-old man presented with a soft-tissue mass on his upper arm. Magneti c resonance imaging analysis revealed an unique mosaic pattern on T2-weight ed images. Needle biopsy disclosed a keratinizing tumor suggesting squamous cell carcinoma. The size of the tumor was 9.5 x 7 x 9.5 cm, one of the lar gest trichoblastomas ever reported. The rarity and gigantic size of the tum or, together with its misleading clinical features, prompted us to report o ur case.