A healthy 65-year-old woman with protruding papules on her neck which had been slowly expanding over the past 10 years visited Soonchunhyang University Seoul Hospital. At first, there were two nodules on the lower right side of her neck. Over the course of 10 years, the lesions spread slowly, and at the time of presentation, were found on the left side of her neck. None of her family members had similar lesions. The lesions were not associated with pain or any symptoms. Also, the patient had no notable past medical history. On physical examination, multiple erythematous, firm, non-tender papules of various sizes (3~7 mm) were observed on the right side of her neck (Fig. 1). A punch biopsy was conducted under local anesthesia. Microscopic examination of the sections stained with hematoxylin and eosin (H&E) showed poorly demarcated tumor intermingling with bundles of dermal collagen fibers. The tumor was composed of smooth muscle fibers that had straight, blunt-ended nuclei with no evidence of nuclear atypia. Neither mitotic activity nor pleomorphism were observed (Fig. 2A, B). Immunohistochemical examination revealed that the tumor cells were positive for actin (Fig. 2C) and desmin (Fig. 2D). Based on clinical and histological examination, the lesion on the patient's neck was diagnosed as multiple cutaneous piloleiomyomas. However, the patient declined surgical or medical intervention.

Multiple piloleiomyomata are known as the most common type of cutaneous leiomyoma1. The condition consists of multiple (on rare occasion, hundreds) of lesions that are small, slowly growing papules. They are typically painful or tender, particularly when compressed or exposed to a cold environment2. Women with multiple piloleiomyomas may also develop uterine leiomyomas. Renal cell cancer also develop in a subset of affected individuals. Hereditary leiomyomatosis and renal cell cancer is caused by germline mutation in the gene encoding fumarate hydratase on chromosome 1q42.3~433. While piloleiomyoma is the most common type of cutaneous leiomyoma in Caucasians, angioleiomyoma is the most common type of cutaneous leiomyoma in Koreans. According to previous reports, cutaneous leiomyomas have been found only on the trunk, lips, and limbs, and to date, there have been no reports on cutaneous leiomyomas on the neck in Korea. On biopsy specimens, piloleiomyomas appear to be composed of poorly circumscribed smooth muscle fibers that are located in the dermis and merge imperceptibly with the surrounding connective tissue4. The tumor is composed of uniform spindle-shaped cells showing interlacing bundle formation or irregular collections of elongated cells with brightly eosinophilic cellularity and blunt-ended or cigar-shaped nuclei. Piloleiomyomata may show very low mitotic activity, one or less mitotic figure/10 high power field (HPF). Tumor cells are usually positive for smooth muscle actin, calponin, desmin, and h-caldesmon. Piloleiomyomas may resemble other painful subcutaneous tumors including eccrine spiradenoma, neuroma, glomus tumor, angiolipoma, neurilemmoma, dermatofibroma. A differential diagnosis between cutaneous leiomyosarcoma and leiomyoma can be made depending on the presence of mitosis5. To summarize, this study reports a rare case of cutaneous leiomyomas that occurred on the neck of a middle-aged woman with no family medical history of the condition.