Epidermal cyst containing numerous spherules of keratin

Sir, Epidermal cyst is classified by the World Health Organization as a tumour associated with hair follicles.1 It is closely related to infundibular cyst, which is defined as a cystic nodule of the dermis lined by stratified squamous epithelium with a granular layer containing laminated keratin.1 We have encountered a peculiar variant of epidermal cyst. A 56‐year‐old man had two subcutaneous nodules on the back, each measuring 10 × 10 mm. They were excised because of a tendency to enlarge. One of the nodules was an ordinary epidermal cyst, whereas the other showed peculiar features. It was soft to the touch and, macroscopically, a cut section showed a cyst with smooth contours. The contents of the cyst were brownish in colour and lumpy in texture, somewhat resembling bone marrow (Fig. 1). Microscopically, the cyst was lined by an epidermis with granular cells and orthokeratinization. The contents of the cyst consisted of numerous closely packed and loosely joined spherules with even dimensions, composed of keratin (Fig. 2a). Spherule formation began from just above the keratinous layer of the lining epithelium (Fig. 2b). Shadow cell‐like foci with mild mineralization were observed very focally (Fig. 2c).