Cutaneous Pilar Leiomyoma: Clinicopathologic Analysis of 53 Lesions in 45 Patients

Abstract

As cutaneous pilar leiomyomas have received little attention in the recent literature, 53 lesions from 45 patients were studied to analyze their clinicopathologic features. There was an equal distribution between both sexes; most patients were adults with a wide age distribution. Both multiple (29 lesions from 21 patients) and solitary tumors (18 patients) were included. Lesions on the extremity (29 tumors) were common in both groups, whereas truncal tumors (11) were confined largely to patients with multiple lesions. In six patients the number of lesions was not specified. The tumors were painful in 17 patients. Three patients had a positive family history of similar lesions. Histologic study revealed ill-defined bundles of well-differentiated smooth muscle cells in the reticular dermis in all cases, although nine lesions had a more nodular pattern. Overlying epidermal hyperplasia was noted in 29 cases (54.7%). Immunohistochemically there appeared to be an increased number of nerve fibers within and surrounding the tumors. Mitotic activity was observed in 15 lesions (28.3%), 13 of which had <1 mitosis per 10 high power fields (HPF); the remaining two lesions had 1-2 mitoses per 10 HPF. Follow-up was available in 10 of these mitotically active tumors and ranged from 9 months to 7 years. There was no recurrence in any of them. We have concluded tentatively that leiomyomas of arrector pili origin may exhibit a low mitotic activity of <1 per 10 HPF and that this does not adversely affect the prognosis for these patients.

Smooth muscle tumors of soft tissue and non-uterine viscera: biology and prognosis

“…Multiple lesions are more common than solitary, except that solitary lesions seem to be more common in the genital and nipple area. 11,12 Histologically pilar leiomyomas may contain nuclear atypia but mitotic activity is exceptional. Mitotically active tumors with atypia have been traditionally classified as leiomyosarcomas.…”

A Case of Multiple Piloleiomyoma on the Shoulder, which is Mistaken for Keloid

“…This hypersensitivity and pain may be induced by the localized compression of the tumor itself, which contains the cutaneous nerve [8], by contraction of the muscle fiber of the tumor [9], or by infiltration of tumor mast cells. However, not all of the causes of this hypersensitivity have been clarified [7]. In our case, the piloleiomyoma appeared as a grouped, protruding pattern with symptoms of acute pain accompanied by pruritus.…”

“…It can emerge on the limbs in both solitary and multiple patterns but solitary is more common [6]. The diameter of the mass of a solitary pattern is smaller than 15 mm, which makes a diagnosis difficult to confirm [7].…”

“…Smooth muscle cells have abundant eosinophilic cytoplasm, blunt-ended and elongated nuclei, and a perinuclear vacuole [8]. They also have low mitotic activity in comparison to leiomyosarcoma [7]. A diagnosis of leiomyoma can be confirmed through immunohistochemical staining to identify smooth muscle actin, consequently, for an accurate diagnosis, a biopsy of the lesion is required.…”

Botulinum Toxin Type A – Treatment of a Patient with Multiple Cutaneous Piloleiomyomas

“…Cutaneous leiomyomas are benign proliferations of smooth muscle cells and are divided into 3 categories: piloleiomyoma, which develops from the arrector pilorum muscle, angioleiomyoma and genital leiomyoma [1,2,3]. …”