Solitary pilar leiomyoma of the nasal dorsum: case report and literature review.

Cutaneous leiomyoma is an infrequently occurring benign tumor that arises from smooth muscle in the skin. Pilar leiomyoma, a subtype of cutaneous leiomyoma, arises from the arrector pili muscle associated with hair follicles. Pilar leiomyoma, particularly in the head and neck region, is rare and frequently misdiagnosed. We report one patient who developed pilar leiomyoma of the nasal dorsum, explore the differential diagnosis and review the characteristics of previously reported individuals with pilar leiomyoma of the nasal dorsum.

What was known?

Pilar leiomyoma is a benign smooth muscle tumor arising from the arrector pili muscle.

Cutaneous leiomyoma most commonly appears on the trunk and extremities.

Introduction

Leiomyoma is a benign smooth muscle tumor most commonly found in the uterus; however, leiomyoma can also be found in the skin and gastrointestinal tract.[1] Cutaneous leiomyomas generally appear on the trunk and extremities; lesser than 1% of leiomyomas are seen in the head and neck.[1] Pilar leiomyoma is a subclass of leiomyoma that develops from the arrector pili muscle in the skin; since, they rarely occur on the head and neck, they are easily mistaken for other cutaneous conditions. We describe a woman who developed a pilar leiomyoma on her nasal dorsum, address the differential diagnosis for nasal lesions and review the characteristics of other previously reported patients with solitary pilar leiomyoma of the nasal dorsum.

Case Report

A healthy 24-year-old female patient presented with a 5 mm × 7 mm red dermal nodule on the bridge of her nose [Figures 1 and 2]. The lesion had been present for 2 years and occasionally itched. The size was relatively stable, increasing slightly when she scratched the nodule and then returning to baseline. There was no personal or family history of uterine leiomyomas. A 2 mm punch biopsy revealed smooth muscle bundles forming a plaque in the dermis [Figure 3]. The bundles of tissue were separated by abundant mucin and immunoperoxidase staining confirmed the presence of smooth muscle actin (SMA) [Figure 4]. These findings were consistent with a pilar leiomyoma of the nasal dorsum.

Figure 1

Distant (a) and closer (b) views of pilar leiomyoma of the nasal dorsum presenting as an erythematous dermal nodule on the bridge of the nose

Figure 2

Right (a), upward (b) and left (c) views of the pilar leiomyoma of the nose of a healthy 24-year-old woman

Figure 3

A low magnification view (a) of the biopsy specimen from the nasal dorsum shows a plaque-like proliferation of cells, which are present in the mid and deep reticular dermis. Closer view (b) abundant mucin between the bundles of cells. The high magnification view (c) the cells have blunt-tipped, cigar-shaped nuclei without atypia or mitoses. These findings are suggestive of a pilar leiomyoma (H and E, a = ×2, b = ×4, c = ×20)

Figure 4

The tumor cells in the dermis express smooth muscle actin (a) The individual cells strongly stain positive (b) confirming the diagnosis of a pilar leiomyoma (smooth muscle actin immunoperoxidase staining using DAB, a = ×4, b = ×20)

Discussion

Cutaneous leiomyomas are an uncommon variant of the typical smooth muscle leiomyoma of the uterus, representing only 3-5% of leiomyomas.[23] Furthermore, lesser than 1% of all leiomyomas are found in the head and neck.[1] Leiomyoma of the skin is divided into three main subtypes based on the origin of the smooth muscle: Pilar leiomyomas originate from the arrector pili muscle, angioleiomyomas originate from the tunica media of superficial blood vessels and genital leiomyomas are derived from the dartos, vulvar or areolar smooth muscle associated with the genitals or breasts.[45]

The clinical presentation of pilar leiomyomas is often non-specific. Lesions are generally firm, reddish-brown or skin-colored papules or nodules.[6] They may be solitary or multiple; when multiple, leiomyomas may develop in a grouped, linear or dermatomal distribution.[45] Patients may complain of itching or pain, particularly with cold or trauma.[45] Pilar leiomyoma most commonly occurs on the extremities or the trunk; it is rare for these tumors to be found on the face and particularly the nose.[14]

Given the nature of the skin findings, leiomyoma is frequently misdiagnosed.[7] In a study of 53 lesions, only 3 were accurately diagnosed prior to biopsy.[4] The differential diagnosis is broad and includes angiolipoma, dermatofibroma, eccrine spiradenoma, foreign body reaction, glomus tumor, histiocytoma, intradermal nevus, lipoma, neurofibroma, persistent bite reaction, post-acne scarring, sebaceous cyst and smooth muscle hamartoma.[34]

Definitive diagnosis of pilar leiomyoma requires microscopic evaluation. Histology reveals haphazardly arranged bundles of spindle-shaped smooth muscle cells with cigar-shaped nuclei.[6] Scant mitotic spindles may be seen, but usually do not exceed 1 per 10 high power field; higher numbers of mitoses may indicate leiomyosarcoma.[4] Myxoid change is commonly observed in the stroma of angioleiomyoma;[8] however, similar to our patient, stromal myxoid change has also been occasionally noted in pilar leiomyoma.[49] Staining with SMA, Masson's trichrome and desmin can be used to confirm the presence of smooth muscle.[410]

We performed an extensive search of PubMed and found only 2 other reported individuals who had pilar leiomyoma of the nose [Table 1]. We used the search terms “leiomyoma AND nose OR nasal.” Patients were excluded if their leiomyomas occurred in the nasal cavity. We also excluded patients whose leiomyomas were described as either vascular (angioleiomyoma) or “bizarre”.[10] A 60-year-old woman who had received radiation therapy for facial acne when younger presented with a 2-cm nasal mass that had been slowly growing for 14 years.[7] In addition, an 86-year-old man presented with a mass on the nasal dorsum that was slowly enlarging for 2 years and impairing his ability to wear glasses.[7] Both patients were treated with excisional biopsy that revealed leiomyoma.[7] Notably, both patients were incorrectly diagnosed pre-operatively (arteriovenous fistula and lipoma, respectively).[7]

Table 1

Characteristics of patients who developed pilar leiomyoma of the nasal dorsum

Treatment of leiomyoma typically depends upon the symptoms and the cosmetic impact of the lesions. Although pain is often refractory to analgesics, several reports suggest the efficacy of muscle relaxants, phenoxybenzamine or calcium channel blockers.[6] Excision is the only curative therapy and recurrence after excision is rare.[67] Leiomyoma is not thought to be a precursor to leiomyosarcoma, so conservative management of leiomyoma is acceptable.[4] However, one recent report presented a patient who developed leiomyosarcoma that originated in a pre-existing pilar leiomyoma.[11] While interesting, this incidental finding does not necessitate excision of all leiomyomas.

Conclusion

Pilar leiomyoma of the nasal dorsum is a benign smooth muscle tumor associated with the arrector pili muscle. Cutaneous leiomyomas most commonly appear on the trunk and extremities; only three patients have been reported who developed pilar leiomyoma on the nose. Pilar leiomyoma presents a diagnostic challenge to the clinician and microscopic examination is required for definitive diagnosis. Patients can be treated medically if the lesions are painful. Alternatively, surgical excision presents a definitive treatment for excellent symptom relief and cosmetic outcome.

What is new?

Pilar leiomyoma of the nasal dorsum has only been described in three patients.

A biopsy of the lesion is essential for making a definitive diagnosis.