Angioleiomyoma in a Rare Location: A Case Report

Abstract

A case report of a 38-year-old man with a 10 year history of left buttock mass associated with pain and numbness. A computed tomography scan showed a subcutaneous enhancing 1cm lesion that was not communicating with surrounding structures to include neurovascular structures. The mass was removed without complication and sent to pathology for extensive review. This case report signifies the importance of maintaining a broad differential with a subcutaneous mass presentation and includes thorough histology and pathology for angioleiomyoma.

Introduction

Soft tissue tumors are defined as mesenchymal proliferations that occur in the extraskeletal, nonepithelial tissues of the body, including the viscera, dura, and lymphoreticular system.¹ They have many different origins including muscle, fat, fibrous tissue, vessels, and nerves. A leiomyoma is a benign smooth muscle cell tumor. Therefore, an angioleiomyoma is a benign tumor of the vascular wall; the muscularis media. Three subtypes of angioleiomyoma include solid type, cavernous, and venous, with solid type being most common.²

The frequency of soft tissue tumors is difficult to estimate because most benign lesions are not excised for pathologic examination.¹ As many as half of all angioleiomyomas diagnosed will be asymptomatic; therefore many patients may choose not to have them excised until they become painful or for cosmetic reasons.

Although one study from 1983 reported a series of over 500 angioleiomyomas, these soft tissue tumors have not been as frequently reported in the recent literature. In a study of 562 cases, 2.5% of cases were located on the trunk with 79% of those occurring in females and 85% consistent with the solid type.² We present a case of a male patient with an angioleiomyoma of the buttock, a location that has not been described in previous publications.

Case Report

The patient is a 38-year-old healthy man who reported to the general surgery clinic with a ten year history of a left buttock mass. The mass was previously asymptomatic until a few months ago when it began to manifest symptoms of pain and numbness around the region, however it had not changed significantly in size. There was no skin discoloration or retraction, and the patient had no gross neurologic deficits of the lower extremity. The patient's exam was remarkable for a one-centimeter by one-centimeter circumscribed mobile soft subcutaneous nodular mass located centrally on the left buttock without skin dimpling or fixation to the underlying muscle. There was a minimal amount of overlying skin hyperpigmentation. A computed tomography (CT) scan showed a subcutaneous enhancing one centimeter lesion not connected to underlying muscle and not related to adjacent neurovascular structures, Figure 1. The patient underwent an excisional biopsy with surgically negative margins.

Figure 1.

CT scan demonstrating enhancement of the left buttock angioleiomyoma.

The mass was removed just superficial to the fascia of the gluteus maximus muscle, Figure 2. Histological analysis revealed a sharply circumscribed subdermal nodule composed of bland spindle cells encircling vascular lumina, Figure 3. Large sinusioidal vessels were observed with small slit-like channels, Figure 4. The stroma contained varying amounts of fibrous tissue and myxoid change. Mitotic activity was absent and there was no evidence of necrosis or hemorrhage. Histologically all surgical margins were negative. Some of the vessels had a smooth muscle layer of moderate thickness, Figure 3. The morphologically bland appearing spindle cells separating the sinusoidal vessels generally had a poorly defined membrane, with pink cytoplasm, and elongated nuclei with rounded cigar-shaped ends. In several areas, these cells merged with the smooth muscle cells. Immunohistochemical evaluation demonstrated that both the spindle cells and the smooth muscle cells surrounding the vessels were strongly immunoreactive for vimentin, smooth-muscle actin, and desmin, Figure 5. There was absence of immunoreactivity for S100 protein excluding a tumor of melanocytic or nerve sheath origin. CD34 highlighted the endothelial cells within the rounded and branching vascular structures. These histologic features support a diagnosis of angioleiomyoma.

Figure 2.

Gross specimen of left buttock angioleiomyoma demarcated by solid arrow.

Figure 3.

Immunoreactivity for desmin highlights the prominent smooth muscle component of this tumor.

Figure 4.

Circumscribed nodule composed of intersecting fascicles of smooth muscle cells encircling numerous vascular channels lined by bland endothelial cells.

Discussion

A superficial soft tissue tumor is a common consult seen by a general surgeon. Despite the benign nature of angioleiomyoma, it is important for this diagnosis to be a part of the differential. The patient described above received the appropriate treatment due to his presentation of pain and abnormal enhancement on CT scan. The histologic findings and presentation are consistent with an angioleiomyoma.

Sixty-seven percent of patients with this tumor will present in their fourth, fifth, or sixth decade.² Angioleiomyomas of the solid type have a strong female predominance, whereas the venous and cavernous types are slightly more common in males. Approximately 89% occur in the extremities with 67% occurring in lower extremity and they are typically <2 cm in size.² The most common complaint is pain that is often paroxysmal and initiated by the slightest touch or exposure of the tumor to environmental stimuli.² The development of multiple lesions is thought to be hereditary and transmitted as an autosomal dominant trait.¹

The most definitive diagnostic method to make a diagnosis is from histologic analysis of an excisional biopsy, along with confirmatory immunohistochemical evaluation. Characteristics of an angioleiomyoma on CT scan have not been well described; however, MRI has been frequently used as it is more sensitive for discerning between the soft tissue layers and can demonstrate a non-specific, well defined, round or oval mass in the subcutaneous or dermal tissue.³ These lesions are usually either isointense or hyperintense to skeletal muscle on T1W1 (low signal magnetic resonance image) images and heterogeneous on T2W1 (high signal on magnetic resonance imaging). Often a hypointense fibrous capsule can be identified forming the peripheral rim.³

Angioleiomyomas consist of a proliferation of spindle cells that tend to intersect with each other at right angles. Immunohistochemical characteristics for angioleiomyoma include vimentin, muscle specific actin (MSA), type IV-collagen, and smooth muscle actin.⁵ These lesions are benign and rarely demonstrate invasion into surrounding structures. They can occur in any tissue containing smooth muscle including arrector pili, smooth muscle wall of arteries, and genital tissues (vulva, nipple, and scrotum). They can also arise anywhere in the gastrointestinal tract and may present with obstruction, intussusception, or volvulus. Cardiac tissue, being comprised of both skeletal and smooth muscle, is also a potential location for angioleiomyoma.

An important distinction to make is between angioleiomyoma, angiomyolipomas, and leiomyosarcomas. Angiomyolipomas are most well known as a renal tumor with an association to tuberous sclerosis. However, angiomyolipomas can also occur as a soft tissue tumor. Beer and colleagues make the distinction that renal angiomyolipomas are HMB45 positive and cutaneous lesions are HMB45 negative.⁴ The cutaneous angiomyolipoma is distinguished from angioleiomyoma by the presence of mature adipose tissue within the tumor. Adipose tissue is present in only 2.5% to 3% of angioleiomyomas, whereas it can occupy approximately 20% to 30% of angiomyolipomas.⁴

Leiomyosarcomas account for 10% to 20% of all soft tissue sarcomas and generally present as a painless firm mass. There is a female predominance and leiomyosarcomas usually involve the skin, deep soft tissue of the extremities, or retroperitoneum.¹ Histologically the tumor nuclei will typically be cigar-shaped and arranged in interweaving fascicles.¹ Lesions located in skin or deep soft tissue of extremities are typically <2cm in size. Tumors located in the retroperitoneum can be very large and remain undiagnosed until found incidentally or compressive symptoms develop.

Treatment options for angioleiomyoma include observation with close interval follow up, biopsy, or surgical excision. There is a recurrence rate of 0.4 % when excised. Ultrasound guided biopsy of the lesion may be indicated if rapid growth of the mass is observed. If malignancy is suspected or found upon fine needle aspiration, then excisional biopsy would be recommended.

Leiomyosarcoma treatment depends on the size, location, and grade of the tumor. Superficial or cutaneous leiomyosarcomas are usually small and have a good prognosis, whereas those of the retroperitoneum are large, often cannot be entirely excised, and cause death by both local extension and metastatic spread.¹ Since the 1983 review of solitary cutaneous and subcutaneous leiomyomas, several case reports have been published and demonstrate the most common presentation is the solid type of the lower extremity with a female predominance and mean age of being 47 years.² This case report defies this commonality, emphasizing the importance of maintaining a broad differential for cases that have a common presentation.

Disclaimer

The views expressed in this manuscript are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.

Conflict of Interest

The authors report no conflicts of interest.