Tongue Mucoceles: a retrospective clinic-pathological evaluation of 240 cases

Even if some authors state that Blandin-Nuhn mucoceles are rare, this study reports 240 cases of Blandin-Nunh mucoceles collected from two different institutions, thus representing the largest case series presented in the literature. The available epidemiological studies conducted on oral mucoceles showed a 15 to 18% frequency, being second only to lower lip mucoceles [4‐7]. In fact, our study confirms that tongue mucoceles have a greater incidence in young people, 50% of them presenting before 20 years of age and with a peak between 10 and 20 years; nonetheless, some cases can occur in infants [13] and in elderly people [14]. In our individual patient data analysis, sex did not appear to be a risk factor, even if there was a slight predilection for female sex.

Tongue trauma (a bite wound or repeated trauma against the lower incisal border) was reported in all our cases as the main aetiological factor: in fact, pathology showed the presence of extravasation mucoceles in more than 95% of the cases (mucous spillage surrounded by connective and granulation tissue - Fig. 2) and, more rarely, the presence of a real cyst (mucous plug/calculus). Extravasation mucoceles are due to the breakdown of the excretory duct, which is usually from being traumatized: such extravasation of mucous into the connective tissue causes a subsequent foreign body reaction (macrophages and neutrophils migration - diapedesis) and the formation of pseudocysts. Moreover, some authors postulated that young people have a higher risk of developing mucoceles because of the sharp margins of the lower incisors, from possible parafunctional habits and, more frequently, from oscillation of the tongue [1‐5].

Considering the clinical presentation, more than 90% of cases (224) involved the ventral surface of the tongue, and among these, the majority (209–93,3%) presented the typical clinical features of extravasation mucoceles (exophytic lesion, pedunculated, light pink in colour, with a tensile/elastic consistency, one centimetre in diameter, without pain, some areas of possible ulceration due to trauma); thus, we confirm the previous literature reports [2]. In some cases, especially at the onset of swelling, the lesion can be bluish in colour due to the extravasation of blood from the involved injured capillaries. The remaining cases presented the features of superficial raised mucoceles (small, i.e., ≤ 5 mm, rounded clear/translucent vesicles) [3]. In our series, some other tongue localizations were detected: 4 of them were on the lateral surface (border of the tongue).

The great majority of our cases presented mucous spillage within a circumscribed cavity in the connective tissue of the submucosa (extravasation-type – 97%), with no epithelium lining the cavity and walls formed by fibrous connective tissue and granulation tissue (foreign body inflammatory reaction - Fig. 3). In a few cases, a real cyst, with epithelium lining the cavity due to a mucous plug or stone, was detected.

Considering the variants described in the literature, ulcerated mucosa (2%), superficial mucocele (8,8%) and sclerosing sialadenitis (8,8%) were the most frequently identified variables in our series, and only one case of myxoglobulosis or “collagenous spherulosis” (mucinous globular structures) was also found. No cases of papillary synovial metaplasia-like change were identified. Nevertheless, it is important for pathologists to be aware of these rare variants to avoid a misdiagnosis.

Superficial mucocele may potentially be confused with immune-mediated subepithelial vesiculobullous conditions (such as pemphigoid or bullous lichen planus) or the vesicles of recurrent herpes simplex virus infection [15]. Their microscopic features are as follows: subepithelial blister containing mucin; often attenuated surface epithelium; possible regeneration of the epithelium across the floor of the blister; and no evidence of extension of subepithelial separation at the periphery of the lesion. Therefore, it is quite simple to understand that such clinical and microscopic features may be mistaken for other conditions, such as the abovementioned pemphigoid, bullous lichen planus or recurrent HSV infection.

Papillary synovial metaplasia-like change is defined by the following criteria: (1) synovial-like membranes thrown into papillary folds and (2) the membrane surface included a thin band of acellular eosinophilic matrix with an underlying condensation of palisaded histiocytes, fibrohistiocytes and/or multinucleated giant cells [16]. Papillary synovial metaplasia-like changes should be distinguished from salivary neoplasms with a papillary cystic growth pattern (such as oncocytic papillary cystadenoma or Warthin tumour). In these cases, the typical mucocele granulation tissue wall was partially replaced by a membrane exhibiting villous folds, a thin superficial band of eosinophilic matrix, and an underlying condensation of palisaded histiocytes, fibrohistiocytes, and/or multinucleated giant cells. Synovial metaplasia is typically seen in other settings, such as in association with breast implants, the bone-cement interface of hip prostheses, tendon implants, testicular implants, and traumatized skin. We believe these changes represent a response to trauma and only rarely arise within oral mucoceles.

Myxoglobulosis, instead, is defined as the presence of hyalinized globular structures either free within the lumen or attached to the granulation tissue wall [17]. However, in the literature, it is reported that such changes often represent a response to trauma and only rarely arise within oral mucoceles.

Considering the diagnostic protocol and differential diagnosis, great value should be given to the history of a rapid onset swelling arising after a trauma (usually a bite), which tends to recur with rapid changes: the swelling, initially floating at the beginning and easily movable, tends to become adherent to the underlying layers. In some cases, at the onset, the lesion may appear bluish in colour, but after some recurrences, it becomes light pink. Among benign and malignant lesions, which can arise on the ventral tongue, HPV-related lesions, pyogenic granulomas, vascular lesions and oral cancer must be considered as differential diagnosis. A fine needle aspiration biopsy (FNAB) can be helpful in the diagnostic workup to exclude other diseases [18], but the correct diagnosis can be reached only with a biopsy. In fact, the presence of a mucous spillage surrounded by connective and granulation tissue (i.e., pseudocysts) or a mucous collection within an epithelial wall is enough to confirm the clinical hypothesis.

Among the different therapeutic approaches, excision, marsupialization, dissection (i.e., excision and enucleation of the gland), cryosurgery, laser ablation and medical therapy have all been described [3, 6, 19‐22]. Careful clinical evaluation of these lesions and preoperative awareness of the surgical anatomy of the glands may minimize the risk of relapses; the anatomical location of the glands, especially Blandin-Nuhn glands, which are located deep into the muscular tissue, must be clearly taken in mind when planning the enucleation of the servicing mucous glands. To diminish the possibility of relapses after excision, the servicing gland must be removed up to the muscular plane, as performed in all the mucoceles removed in our study. An additional movie file shows this in more detail (see Additional file 1). Nevertheless, we had 4 relapses that occurred in males and one sensory paraesthesia of the border of the tongue. Considering the other therapeutic approaches, some interest must be considered for marsupialization of the lesion, which can be helpful to resolve large mucoceles, or in paediatric patients before performing definitive surgical enucleation [19]. Another proposed approach is the administration of intralesional steroids, which has been advocated as a possible alternative therapy when clinicians decide to avoid surgery [23]. Recently, moreover, a case report [24] and a clinical trial [25] showed that laser can represent a valid substitute for the cold scalpel in the surgical management of mucoceles or in promoting the healing of mucocele marsupialization [26], but the majority of the treated lesions were in the lower lip, thus with superficial servicing glands. For these reasons, traditional surgical excision with enucleation of the deep servicing gland seems to be the most reliable therapeutic approach.