Oral Focal Mucinosis - Etiology, Clinical, and Histopathological Features

What Is Oral Focal Mucinosis?

Oral focal mucinosis (OFM) is primarily termed as the oral counterpart of the condition called cutaneous focal mucinosis (CFM) or cutaneous myxoid cyst. This condition was initially discovered in 1974 by Tomich when he proposed that oral focal mucinosis was a primary oral manifestation of cutaneous focal mucinosis characterized by localized myxoid degeneration of connective tissues.

OFM or oral focal mucinous can present mainly as benign or inflamed soft tissue swelling in the oral mucosa. This swelling can either be pedunculated (swelling with a stalk) or sessile (flat), with the gingiva being confirmed as the most common site for the occurrence. Moreover, these are challenging and can only be diagnosed through clinical or radiologic findings.

What Is the Etiology of Oral Focal Mucinosis?

Oral focal mucinosis (OFM) is an uncommon and asymptomatic condition that is difficult to diagnose. These lesions appear to be submucosal and slow-growing nodules. Oral focal mucinosis is a projection of the cutaneous focal mucinosis disease in the oral cavity without cutaneous systemic manifestations and unknown etiology.

Moreover, the pathophysiology of oral focal mucinosis remains elusive and may not be clearly understood. However, it is found that it is characterized mainly by the deposition of mucin in connective tissue locally, leading to specific mucoid degeneration.

The incidence of this condition is higher in females than males, with the highest prevalence in the fifth decade of life.

What Are the Clinical Features of Oral Focal Mucinosis?

Oral focal mucinosis and cutaneous focal mucinosis are benign (non-neoplastic) lesions. They are linked based on their pathophysiology, which indicates trauma or injury to the connective tissues without showing any specific symptoms. As the etiology of oral focal mucinosis is unknown, it is hypothesized as the overproduction of hyaluronic acid by fibroblasts in response to the trauma to connective tissues. Some of the standard features seen in these lesions are mentioned below -

• The lesion appears as loose nodules that do not adhere to the deeper structures.

• The lesion merges into the same color as oral mucosal membranes and skin in case of cutaneous focal mucinosis.

• About 68 % of oral focal mucinosis is commonly seen on the gingival tissues contributing to the major lesion location, and up to 14 % may occur in the palate.

• The lesions may appear broad-based nodular lesions and are rarely reported on the tongue.

• These lesions may frequently appear on clinical examination extending to the underlying muscle layer without any superficial inflammatory surface around the borders or adjacent to the location of the lesion.

What Is the Differential Diagnosis of Oral Focal Mucinosis?

As oral focal mucinosis is present as a local overgrowth on the gingiva in the oral cavity and therefore it needs correct differential diagnosis establishment from similar lesions such as -

• Traumatic or oral fibromas.

• Gingival epulis lesions.

• Oral pyogenic granuloma.

• Oral mucocele.

• Lesions of the palate.

• Benign tumors of the salivary gland.

• Oral tumors of mesenchymal origin.

What Is the Difference Between Oral Focal Mucinosis and Pleomorphic Adenoma Tumor?

Pleomorphic adenoma (PA) is one of the most common benign salivary gland tumors resembling oral focal mucinosis lesions. Therefore, both these lesions are challenging to differentiate. Some of the features that can help determine these two lesions include the following -

In pleomorphic adenoma, the mass or lesions are -

• Painless.

• Firm.

• Slow-growing.

• Have smooth and lobulated consistency.

• Mainly found on the posterior or lateral surface of the palate.

In oral focal mucinosis, the lobulated appearance may not be seen in most cases. However, still, it may be clinically challenging to diagnose these lesions based on just clinical or radiographic findings.

What Are the Histopathologic Features of Oral Focal Mucinosis?

The histopathological examination of oral focal mucinosis mainly shows some of the following features such as -

• Relatively well-demarcated areas of the lesions are composed primarily of a loose matrix or myxomatous connective tissue.

• There are slightly enlarged oval-shaped fibroblasts present.

• The lesion appears lobulated and with circumscribed and unencapsulated margins.

• The superficial portions of the lesion attenuate over the rete ridges of the superficial squamous epithelium. In the deep layers, the lesions are observed in the involvement and displacement of skeletal muscle fibers.

• According to case reports, the rete ridges in the overlying surface layer or epithelium are blunted without significant changes or alterations in the squamous epithelium layer.

How to Diagnose Oral Focal Mucinosis?

The clinical appearance of oral focal mucinosis lesions is very non-specific because they appear as singular nodules and may clinically resemble other potential provisional diagnostic lesions, such as -

• Fibroma.

• Fibrous or gingival epulis.

• Fibrous hyperplasia lesions.

• Peripheral giant-cell granulomas.

• Oral pyogenic granuloma.

• Periodontal abscess.

• Fibroepithelial oral polyp.

Therefore, an accurate diagnosis can be only formulated through biopsy and subsequent examination by histopathology and microscopy examination.

Conclusion:

Oral focal mucinosis lesions are difficult and uncommon clinicopathologic entities that should be suspected in patients with cutaneous focal mucinosis. Also, due to their resemblance to multiple oral lesions, biopsy and histopathologic examination of the tissue will confer clarity on this diagnostically challenging and rare oral condition.