Figure 3 and 4: HIstopathological pictures of cutaneous leiomyoma showing smooth muscles arranged in interlacing fascicles.
DISCUSSION
Cutaneous leiomyomas are rare benign, painful tumors arising from smooth muscle fibres. According to site of origin, the types are pilar leiomyoma, angioleiomyoma and dartoic leiomyoma, pilar leiomyoma being the most common type. Pilar leiomyomas often occur as multiple and disseminated or segmental pattern in 80% of the cases.10 Multiple lesions are inherited as autosomal dominant trait and may be associated with a condition termed Reed syndrome. The predisposing gene for Reed syndrome is localized in chromosome 1q42.3-43 which encodes Fumarate Hydratase (FH) gene. FH is involved in Krebs cycle for conversion of fumarate to malate. Along with this, FH is also believed to be a tumor suppressor gene and mutation of FH leads to increased risk for developing renal tumors.9,11 The lesions in multiple pilar leiomyomas can be arranged in disseminated , blaschkoid or segmental(zosteriform ) patterns. Segmental pattern is further categorized into type 1 and type 2 segmental.
Histopathologically, pilar leiomyomas are circumscribed, non-encapsulated tumors comprised of smooth muscles bundles arranged in interlacing patterns, and sometimes in whorled pattern. The cells have abundant eosinophilic cytoplasm and elongated nuclei with blunt ends.
Treatment of pilar leiomyomas remains frustrating. If the lesion is solitary or few in number, excision can be considered. However, multiple lesions are often treated symptomatically for pain. The treatment options for pain in leiomyomas are calcium channel blockers like nifedipine which blocks influx of calcium into smooth muscle, alpha adrenergic blocking agents such as doxazocine and phenoxibenzamine, and gabapentin and topical 9% hyoscine hydrobromide. CO2 laser, cryotherapy and electrocoagulation are alternative treatments.7