Sialoblastoma in cheek region: Report of a case

1. Introduction 

Sialoblastomas are very rare tumors of the salivary gland that occur during childhood and that have basaloid epithelial and stromal components with disparate grades in histomorphology [1]. They are also known as embryomas. Sialoblastomas constitute 3–5% of all salivary gland tumors [2], [3].

Given this rarity, the biological behavior of sialoblastoma is poorly defined. It is usually localized to the parotid or submandibular glands [1], [4], [5]. The recommended treatment is early surgery [3], [6]. In this report we describe a malignant sialoblastoma at cheek region in one such patient. The uniqueness of this case lies in its location and behavior; it occurred in the cheek region, away from the major salivary glands where it usually arises and it relapsed after 3 months.

2. Case report 

A 5-year-old boy was seen for the first time at a regional hospital with swelling in the right cheek region. Initially, the diagnosis was thought to be mumps because of painful enlargement and treated medically. However, he did not respond to this treatment and was referred to another university hospital. On examination, gradual, painful enlargement of a mass was identified. Ultrasonography showed a 13mm×10mm hypoechoic mass in the right cheek region. An excisional biopsy was performed and the pathology report revealed a sialoblastoma.

The mass relapsed after 3 months and the patient was referred to our clinic. We identified a solid, 3cm×2cm, painful mass in the right cheek area. There were no regional lymph nodes or signs of any other systemic disease. MR imaging showed a mass in the right buccal region measuring 2.5cm×2cm (Fig. 1).

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Fig. 1. MR imaging shows a mass in the right buccal region.

We performed a wide, local excision under general anesthesia. The mass, which extended to the masseter muscle, was excised totally, with safe margins (Fig. 2). The pathology revealed a sialoblastoma with mitotic activity, findings of cell necrosis with cytological atypia, and infiltration of the surrounding soft tissue (Fig. 3a and b). The patient was deemed to have a malignant sialoblastoma and directed to the pediatric oncology department for further chemotherapy treatment.

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Fig. 2. Intraoral excision of the mass.

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Fig. 3. (a and b) The tumor is composed of nests of epidermoid cells arranged in a vague acinar fashion. Sialoblastoma with mitotic activity, findings of cell necrosis with cytological atypia, and infiltration of the surrounding soft tissue.

3. Discussion 

Sialoblastoma, also known as embryoma, was first described in 1966 by Vawter and Tefft [7]. Congenital tumors of the major salivary glands arise from the mesenchyme or from epithelial structures [4]. Sialoblastomas usually originate from the ductal epithelium, with participation of the surrounding myoepithelial cells [4]. It has basaloid epithelial and stromal components, with disparate grades in histomorphology [5].

Batsakis classified perinatal salivary gland tumors into four categories: [8], [9] (1) benign tumors, e.g., pleomorphic and monomorphic adenomas; (2) hamartomatous tumors; (3) this group, which includes sialoblastoma, and is reminiscent of the embryonic epithelial anlage of the major salivary glands; and (4) malignant tumors [4].

Sialoblastoma has a number of different names, including congenital basal cell adenoma, basal cell adenoma, basaloid adenocarcinoma, and congenital hybrid basal cell adenoma-adenoid cystic carcinoma [10]. Sialoblastoma can be benign or malignant histologically. The criteria for malignancy include the invasion of nerves or vascular spaces and ancillary findings of cell necrosis with cytological atypia and mitotic activity [1]. In our case the tumor showed mitotic activity, findings of cell necrosis with cytological atypia, and infiltration of the surrounding soft tissue. According to these findings the tumor was diagnosed as malignant sialoblastoma.

The frequency of sialoblastoma is unknown. Since it is a rare salivary gland tumor, the behavior of this tumor is unclear. It usually arises from a parotid or submandibular gland [1], [4], [5]. Other localizations are not well described in the literature. In our case, the sialoblastoma occurred in the cheek region, away from the major salivary glands. Because this rare localization and atypical behavior; the patient was diagnosed as mumps in the first place.

The best treatment for sialoblastoma is early surgery [3], [6]. The mass should be excised totally and widely. The primary concern in the treatment of sialoblastomas is local recurrence. The literature describes at least five patients with local recurrence [10], [11], [12]. In our case, the recurrence occurred after 3 months and we had to perform a second surgery to treat it. Adjuvant therapy for sialoblastoma treatment remains controversial, chemotherapy may be an alternative treatment for relapsed or metastatic sialoblastomas [12], [13]. Although chemotherapy is controversial for sialoblastoma treatment, adjuvant chemotherapy was planned by pediatric oncology department.

Although sialoblastoma is a rare salivary gland tumor of childhood, this tumor should be recognized by otolaryngologists and pathologists. The treatment plan must consider the natural behavior of this tumor, such as local recurrence. Early surgery must be performed and the patient must be followed to detect local recurrences.