Oral soft-tissue myxoma

Abstract

Oral soft-tissue myxomas of the oral cavity have been sparsely cited in the medical literature worldwide. This could be due to other clinically and/or histologically similar lesions requiring accurate differential diagnosis by experienced physicians and pathologists. Although myxomas are benign and do not metastasise, they have higher rates of recurrence and deserve proper attention and to be reported as well. Soft-tissue myxomas of the oral cavity are extremely rare and very few cases have been reported in the literature. The article describes a soft-tissue myxoma in a male patient in his 40s and review of published cases.

Background

Myxomas are benign tumours, derived from primitive mesenchymal tissue. Currently, these are considered to be rare, locally infiltrative tumours of connective tissue origin consisting exclusively of undifferentiated stellate cells in an abundant myxoid extracellular matrix.

Myxomas that arise in the oral cavity are of two main types: odontogenic and soft tissue. Odontogenic myxomas (OM) occurs primarily within the jaws whereas soft-tissue myxomas (STM) are deeply situated lesion that can occur anywhere owing to its primitive cell origin, identified mostly in the skeletal muscles, subcutaneous tissues and fascial planes of the maxillofacial regions.¹

Intraoral STM are extremely rare lesions and very few reports have been reported in the literature so far. Therefore, this article entails a rare case of STM on the lip in a middle-aged male patient.

Case presentation

A healthy middle-aged male patient reported with swelling on the lower lip. He first noticed an asymptomatic swelling 8 months back when it was small and then it slowly reached to the present size. He gave a history of fall from the bed nearing the beginning on the lesion, but cannot recollect clearly. On intraoral examination, a dome-shaped, smooth surfaced, sessile growth measuring around 2×2 cm was present 1 cm from the midline on the right side of the lower lip (figure 1). The growth was non-tender, soft in consistency and appeared fluctuant at one point. On the basis of clinical features, a differential diagnosis of fibroma and mucocele was made.

Figure 1.

Photograph shows laser-assisted resection of soft-tissue growth on lower lip.

Investigations

A routine blood investigation was advised and after physicians consent, an excisional biopsy using lasers was carried out under local anaesthesia. On histopathological examination with routine H&E stain, the sections revealed parakeratinised stratified squamous epithelium with mild hyperplasia overlying a loose and myxomatous connective tissue. The stroma was moderately cellular and hypovascular with slightly hematoxyphilic hue and with few thin blood vessels. Stellate and spindle-shaped fibroblasts seen in an amorphous mucinous connective tissue were suggestive of STM (figure 2). Alcian blue stain at pH-2.5 showed positivity of the deeper stromal component indicating the presence of hyaluronic acid and acidic glycosamino glycans within the mucoid stroma (figure 3). The myxomatous area showed a moderate amount of reticular fibres on reticulin staining ruling out the possibility of oral focal mucinosis (figure 4). Further immunohistochemical analysis showed negative expression of S-100, hence confirming the diagnosis of STM (figure 5). The patient underwent regular follow-up and showed no evidence of recurrence.

Figure 2.

A lower magnification H&E photomicrograph showing the presence of a loose stroma with scattered cells along with delicate wavy collagen fiber bundles.

Figure 3.

Positive Alcian blue staining of stroma indicating the presence of hyaluronic acid and glycosaminoglycans (40×).

Figure 4.

Reticulin stain showing moderate positivity indicating the presence of reticular fibers (40×).

Figure 5.

Negative immunostaining for S-100 (10×).

Differential diagnosis

On the basis of clinical features a provisional diagnosis of mucocele and differential diagnosis of fibroma were made. During histopathological evaluation, myxomatous degeneration, oral focal mucinosis, nerve sheath myxoma, myxoid liposarcoma and myxofibrosarcoma were considered.

Outcome and follow-up

The patient underwent regular follow-up and showed no evidence of recurrence.

Discussion

Myxomas were first described by Virchow in 1871. Intraosseous myxomas are more common than STM in the head and neck region and the mandible is more frequently involved than the maxilla. STM are reported in the head and neck in both somatic and supporting adjacent tissues. Such cases that occur predominantly within the jaws, that is, the tumours that are derived from the dental papilla, dental follicle, or periodontal tissue are described in the literature as OM.²

STM of the oral cavity are extremely rare. The clinical presentation of myxomas reported in the oral cavity is not pathognomonic and is variable. They show a slight female prediction with the largest number of cases reported in the fourth decade.

According to the reports published by Epivatianos et al, palate was the most commonly affected site in the oral cavity followed by the buccal mucosa, the lips and the floor of the mouth.³ Recently, Okubo et al have reported an additional case of STM arising on the left buccal mucosa.⁴ On review of previously published cases in English literature, a total of 42 cases (including the present case) were found as shown in table 1. However, few more cases are reported in Japanese and other languages.

Table 1.

Review of literature of intraoral soft-tissue myxomas1 3 4 10–19

	Author	Year	Site
1	Daniels et al	1908	Soft tissues over the mandible
2	Tholen et al	1936	Palate
3	Babbit and Pfeiffer	1937	Palate
4	Sealey et al	1948	Palate
5	Salama and Hilmy	1951	Palate
6	Bernier	1959	Upper lip
7	Bernier	1960	Palate
8	Dutz and Stout	1961	Interdental papilla
9	Spengos and Schow	1965	Cheek
10	Traiger and Lawson	1969	Cheek
11	Pradhan et al	1972	Lower lip
12	Tahsinoglu et al	1975	Hard palate
13	Lucas RB	1976	Palatal gingiva
14	Matsumura et al	1977	Palate
15	Swart et al	1977	Floor of the mouth
16	Elzay and Dutz	1978	Hard palate
			Buccal mucosa
			Upper lip
			Retromolar pad
20	Campos et al	1980	Alveolar Ridge
21	Rapidis AD et al	1983	Hard Palate
22	Ferrari Parabita et al	1986	Labial mucosa
23	Siar et al	1986	Palate
24	Quintal et al	1994	Palate
25	Andrews et al	2000	Buccal mucosa
26	Shimoyama et al	2001	Gingiva
27	Chang et al	2001	Gingiva
28	Mishra et al	2003	Buccal/labial mucosa
29	Ramaraj et al	2003	Buccal sulcus
30	Perrotti et al	2006	Gingiva
31	Epivatianos et al	2007	Buccal mucosa
32	Adebiyi KE et al	2012	Gingiva-−3 cases
35	James L et al	2012	Tongue
36	Shenoy et al	2014	Buccal mucosa
37	Manjunath et al	2014	Buccal mucosa
38	Ha et al	2020	Tongue
39	Sharma et al	2021	Palate
40	Mariz et al	2021	Palate
41	Okubo et al	2021	Buccal mucosa
42	Present authors	2022	Labial mucosa

Cases reported only from English literature (modified from previous published cases).

The aetiology of myxoma remains unclear but there are several theories about its pathogenesis, the most accepted one is the presence of altered fibroblasts that could produce an excess of mucopolysaccharides. These altered fibroblasts are unable to form mature collagen even if some cells could retain this capacity. They grow at varying rates from slow to sometimes no growth at all over a period. They are usually well-circumscribed, round to oval painless mass with no remarkable capsule.⁵

Grossly, it appears as a gelatinous mass, greyish in colour, having a glistening mucoid appearance.

Myxomas are benign, uncapsulated, infiltrate the surrounding tissue, have a high recurrence rate, and may prove fatal if infiltrate into vital structures.¹ Histologically, tumours are composed of hypocellular areas predominantly of stellate-shaped cells in the background of abundant myxoid stroma and irregularly streaming reticular fibres. There is no evidence of cellular pleomorphism and mitotic figures. Blood vessels are rarely present.

STM show a characteristic infiltration type of growth pattern into the adjacent tissue owing to their slippery nature and never metastasise to distant organs. Grossly, myxomas are gelatinous in consistency due to the presence of mucoid material inside them. The accumulation of the latter imparts a blue-grey hue on a microscopic examination. Electron microscopy and biochemical studies revealed the presence of polysaccharides, glycosaminoglycans or glycoproteins. In particular, STM exhibit an abundant amount of a non-sulfated glycosaminoglycan known as hyaluronic acid and sulfated glycosaminoglycan known as chondroitin sulfate, keratan sulfate and dermatan sulfate.⁶

The differential diagnosis of oral STM poses a great challenge with other lesions showing myxomatous degeneration. Therefore, a proper final diagnosis can only be established after a thorough histopathological examination of the entire lesion.⁵ The following differential diagnoses should be considered: oral focal mucinosis, nerve sheath myxoma. Some malignant tumours that show myxoid changes such as myxoid liposarcoma and myxofibrosarcoma should also be kept in mind while making the diagnosis.⁷ Myxomatous degeneration is a common occurrence in an extensively growing mass, for example, fibrous tumours.⁴

Oral focal mucinosis shows the presence of a localised myxoid area surrounded by a dense fibrous connective tissue and can be differentiated from myxoma by the absence of reticular fibres in the myxoid stroma. Reticular fibres in myxoma can be easily appreciated by using reticulin stain and the lesion is not demarcated from the surrounding fibrous connective tissues.

Nerve sheath myxoma is a benign tumour of neural origin arising from Schwann cells. It is a well-circumscribed, non-encapsulated myxomatous lesion composed of spindle-shaped cells showing S-100 strong immunoreactivity confirming their neural origin and arranged in fascicles separated by fibrous septae. Therefore, immunohistochemistry may be helpful for the differential diagnosis from STM that display negative staining for S-100. On the other hand, STM show negative staining for S-100 and Desmin, but positive for vimentin staining. Special stains have also been proven to help diagnose such lesions.⁸

Excisional surgery remains the treatment of choice. Though the tumour does not metastasise, it can still recur due to its jelly-like consistency, lack of capsule, an infiltrative growth pattern into the adjacent connective tissue. Therefore, the tumour often requires a wider excision involving the adjoining normal tissue.⁹

Patient’s perspective.

I am relieved of the abnormal bulge like feeling in the mouth which had started to feel especially while eating. After surgery the healing of wound was good and there was no problem after the surgery.

Learning points.

• Oral myxomas may be misdiagnosed easily due to their non-characteristic nature and are often seen as a part of myxomatous degeneration.

• Special stains and immunohistochemistry markers such as S-100 have been proven to help diagnose soft-tissue myxoma and similar lesions.

• They should be reported well, keeping in mind the recurrent nature of the tumour.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).