Solitary superficial acral angiomyxoma: an infrequently reported soft tissue tumor.

Superficial angiomyxomas (SA) are clinically variable, infrequent, benign skin lesions. They are usually located on the trunk, but can also appear on the lower limbs, head, and neck. The present case, hence, is unusual, because the lesion developed on the toe. They are diagnosed histologically, and are characterized by being poorly delimited tumors with the presence of interstitial myxoid material and scanty cellularity. We discuss the clinical and histological features of digital SA as well as a brief outline of other myxoid lesions.

What was known?

Solitary angiomyxomas are usually solitary, potentially locally recurrent but nonmetastatic myxoid tumours usually on trunk. However they may be seen on head and neck and sometimes on the lower limb. Digital localisation is very rare. They are often mistaken for digital myxoid cysts.

Introduction

Superficial angiomyxomas (SA) is an under recognized lesion, which encompasses the majority of lesions referred in the earlier literature as “cutaneous myxoma”. SA, first reported by Allen et al. in 1988[1] as a poorly circumscribed lesion composed of myxoid nodules containing thin-walled capillaries and spindle-shaped or stellate fibroblasts commonly present as a nodule on the trunk, head, and neck, or the genital region. Originally proposed to be synonymous with cutaneous focal mucinosis, trichofolliculomas and trichodiscomas, Calonje et al.[2] disagreed with this hypothesis concluding that SA was a distinct entity. They have only been infrequently described on the digit mimicking a digital myxoid cyst.[34] We describe one such case.

Case Report

A 35 year old female came with complaints of a red raised lesion on the left fourth toe since 5 years. The lesion had increased very gradually in size, and had recently become painful to touch. There were no other lesions present on the skin. There was no preceding history of trauma to the lesion. On examination, there was a firm round tender tumor, 5 × 6mm2 in size on the lateral aspect of the 4th toe [Figure 1]. Histopathology revealed a normal epidermis with a dermal tumor filled with a mucoid material, and surrounded by a fibrous tissue. The tumor cells were arranged in a storiform and fascicular growth pattern. At higher magnification, the tumor consisted of small thin-walled blood vessels and spindle-shaped or stellate tumor cells without cytological atypia in addition to the mucoid material [Figure 2]. We diagnosed the skin condition as SA based on clinical and histologic findings of the tumor. The lesion was excised under local anesthesia but the patient reported a recurrence after 3 months of excision [Figure 3].

Figure 1

A firm round tender tumor on the lateral aspect of the 4th toe

Figure 2

H and E (×40) showing a dermal tumor filled with a mucoid material, and surrounded by a fibrous tissue. The tumor cells are arranged in a storiform pattern. At higher magnification (H and E-×400-inset), the tumor consisted of small thin-walled blood vessels and spindle-shaped or stellate tumor cells without cytological atypia in addition to the mucoid material

Figure 3

Recurrence of the tumor after 3 months of excision

Discussion

Despite being first described in 1988, SA is still a poorly recognized cutaneous tumor. SA was first described and named as a cutaneous myxoma of Carney's complex by Carney et al. in 1986.[5] In 1988, Allen et al. reported cutaneous tumors that were histologically similar to cutaneous myxomas of Carney's complex but had no evidence of the complex and named it SA (due to a predominant vascular component). They reported 30 SA's in 28 patients (16 male and 12 female patients) whose ages ranged from 4 to 78 years (mean, 39 years). Tumor size varied from 0.5 to 9 cm, with the majority measuring 1 to 5 cm. Eleven tumors (37%) were located on the trunk, 10 (33%) on the lower extremity, 5 (17%) on the head or neck, and 4 (13%) on the arm.[1]

SA are usually solitary, potentially locally recurrent but nonmetastatic, and occur most commonly in the fourth decade, as in our case. Histologically, this is a poorly demarcated lesion characterized by myxoid stroma with mucin pools and prominent vascularization. An inflammatory cell component is usually seen. Strands of squamous or basaloid cells, or epidermoid cysts, which probably represent entrapped adnexal structures, are not uncommon. It is negative for S100, SMA as well as muscle specific actin, with occasional positivity for CD34. Multiple SA, especially those located on the external ear, are considered pathognomonic for Carney complex, an autosomal dominant disorder associated with multiple myxomas (cardiac, cutaneous, and mammary), blue nevi, lentigines, psammomatous melanotic schwannoma, and endocrine overactivity.[6] Our patient did not seem to have Carney's complex because her cutaneous tumor was not accompanied by non-cutaneous myxomas, pigmentation of the skin or mucous membrane, or endocrine disorders. The relative frequencies of myxoid lesions summarized in the Table 1 have to be kept in mind, as it seems wise to rule out the most common tumors before considering exceptional diagnosis. Although the exact incidence is unknown, in the index article, only 27 solitary tumors were identified among 4500consults seen over 23 years.[1] Satter reviewed approximately 180000 surgical pathology cases over past 10 years and found only two cases of SA, other than the one that was the subject of his article.[8] To the best of our knowledge, there has been only two published report on digital superficial angiomyxoma, the first one describing two subungual lesions occurring on the thumb in one case and on the fifth toe in another case,[4] and the second article describing a nodular lesion on the finger mimicking a digital myxoid cyst.[3] The differential diagnosis of a mucinous dermal nodule is vast. A close mimic is a digital myxoid cyst. However, a digital myxoid cyst almost always arises on or around the distal interphalangeal (DIP) joint, while frequently developing on the dorsal digits between the DIP joint and the proximal nailfold.[9] Digital myxoid cysts histopathologically tend to show a well-circumscribed, large deposit of mucinous material associated with some fibroblasts in the upper to middle dermis, and there is usually no great degree of vascularity. Cutaneous focal mucinosis is largely acellular with very few blood cells, and it lacks a lobular architecture and stromal neutrophils, thus those findings do not correlate with the features observed in our patient's lesion.[2] Another myxoid lesion that can occur in the finger, namely, acral persistent mucinosis, can be easily ruled out because of its characteristic symmetrical distribution of multiple papular lesions on the back of the hands and forearms. In conclusion, the features most useful to differentiate a SA from other myxoid tumors include its superficial location, lack of atypia, stromal inflammatory infiltrate, and a frequent association with an entrapped epithelial component. Rare cases of neoplastic, true myxoma with poor vascularity, as defined by Stout[10] have been reported.

Table 1

Relative frequencies of myxoid lesions[7]

Complete excision and follow-up review are recommended as long-term follow-up studies have revealed local recurrence of the tumor (30 to 40%) associated with inadequate resection.[12] Our patient had a recurrence after 3 months of excision possibly because of incomplete removal of the tumor. Close follow up is also mandated since SA can represent the earliest and only manifestation of the Carney's syndrome.

What is new?

The digital location of this distinct but infrequently reported benign tumour, mimicking a digital myxoid cyst is highly unusual.