Cylindroma with Stromal Adipose Tissue Metaplasia versus Arising in a Background of Nevus Lipomatosus

Nevus lipomatosus superficialis is a rare type of connective tissue nevus. Cylindroma is a benign skin appendage tumor with a predilection for the scalp of older females. We describe the case of a 56-year-old woman with a scalp lesion demonstrating histopathologic features consistent with benign cylindroma arising within a nevus lipomatosus superficialis. To our knowledge, this lesion has not been raised in the literature in the differential for cylindroma with what is presumed to be stromal adipose metaplasia. 1. Introduction Nevus lipomatosus superficialis (NLS) is a rare type of connective tissue nevus that was first described in 1921 by Hoffmann and Zurhelle [1]. It is characterized by the ectopic presence of mature adipose tissue in the dermis. Clinically, two variants of NLS are recognized: classic and solitary. The classic variant of NLS is present in the first two decades of life as aggregations of flesh-colored or yellow papules and nodules with a predilection for the buttocks, upper posterior thighs, and lumbar back. The solitary variant of NLS is present in adults, predominantly after the third decade of life, as isolated papules or nodules anywhere on the skin. Compared with the classic variant of NLS, the solitary variant shows more frequent involvement of non-pelvic-girdle areas of skin, including the axilla, arm, knee, ear, and scalp [2]. Unlike nevus sebaceus of Jadassohn, it is rare for appendageal tumors to develop within NLS. Cylindroma, in particular, is a benign skin appendage tumor of hair follicle origin [3] with a predilection for the scalp of middle-aged to elderly females. We present the case of a patient with a scalp lesion demonstrating histopathologic features consistent with benign cylindroma arising within a nevus lipomatosus superficialis. 2. Case Presentation A 56-year-old woman presented with a 1.1？cm skin-colored nodule on the right anterior scalp at the hairline. The remaining physical examination was noncontributory. Her medical history included chronic obstructive pulmonary disease and hypothyroidism. An excisional biopsy was performed. Microscopic examination showed a poorly circumscribed tumor with variably-sized, irregularly-shaped islands of basaloid cells ensheathed in bright eosinophilic bands (Figures 1 and 2). The islands occupied the dermis and extended into the subcutaneous fat to the depth of fascia. A band of compressed papillary dermis separated the basaloid islands from the overlying epidermis. The tumor islands were dispersed by an expanded stroma containing adipocytes distributed circumferentially