Management and treatment of a sialoblastoma of the submandibular gland in a neonate

1. Introduction 

Less than 3% of salivary gland tumors occur in children and the vast majority occurs in the second decade of life [1]. During the first year of life, hemangiomas are the most common. Sialoblastomas have been reported to occur predominantly in the parotid gland [2], [3]. We report one case of sialoblastoma of the submandibular gland; we describe its clinical, radiological and histopathologic features and discuss the differential diagnosis and treatment.

2. Case report 

A 3 days old girl was referred to our department after birth for a left cervical mass that had already been detected by antenatal echography and foetal Magnetic Resonance Imaging (MRI) (Fig. 1). The prenatal radiological aspect was in favour of a congenital hemangioma.

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Fig. 1. T2-weighted foetal MRI showing the large left cervical tumor: coronal (A) and saggital (B) views.

The little girl weighing 3400g was born spontaneously at term by vaginal route. Examination revealed a large hard mobile mass going from the left inferior parotid region to the left submandibular region (Fig. 2). The swelling did not have any mass effect or inflammation; the airway at birth was not compromised. There was no facial palsy. An echography was performed by the same radiologist who is specialized in vascular malformations and had already performed the foetal exams. As all the echographic and clinical criterias of hemangioma were not met, an MRI was realized. The MRI showed a well circumscribed soft tissue mass which dimensions were 60mm×42mm×52mm with a parapharyngeal extension. The tumor was isointense to muscle on T1-weighted images with a post-contrast enhancement; on T2-weighted images the lesion had high-intermediate signal intensity (Fig. 3).

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Fig. 2. Photography of the 3 days old girl showing the large swelling going from the left parotid region to the left submandibular region.

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Fig. 3. (A) T2-weighted coronal view showing an intermediate signal intensity of the tumor. (B) Axial post-gadolinium T1-weighted images showing a rather high contrast enhancement of the mass.

As some of the clinical and radiological aspects were not typical of hemangioma, a surgical biopsy was decided for excluding a sarcomatous lesion like congenital rhabdomyosarcoma or fibrosarcoma. The mass was diagnosed as sialoblastoma by the histopathologists.

A CT scan without contrast injection was realised to better evaluate the relations of the tumor with mandible. It showed a soft tissue mass isodense to muscle with no sign of osteolysis or bone invasion.

A surgical treatment was decided during a multidisciplinary consultation including a pediatric cancerologist, two ENT surgeons, a radiologist and a neonatologist, indeed, based on MRI and CT scan findings, the mass appeared suitable for total resection. Excision was made under general anaesthesia through a parotid-type incision with facial nerve monitoring at 10 days of age. The mass was found to be well encapsulated, distinct though adjacent to the left parotid gland. The facial nerve trunk was identified and preserved, so was its buccal branch that was adherent to the tumor. Tumor was found to arise from the left submandibular gland; therefore a monobloc resection was performed (Fig. 4).

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Fig. 4. Intraoperative view showing the tumor that is about to be removed in monobloc with the submandibular gland (white arrow).

Macroscopic examination revealed a circumscribed, firm, multilobulated, orange or beige solid mass measuring 7.5cm×4.5cm×6cm and weighing 69g (Fig. 5). Microscopic examination after hematoxylin eosin saffron staining showed a tumor composed of islands and nests of epithelial cells with basaloid appearance separated by bands of fibrous stroma (Fig. 6). The mitotic rate was 10 per 10 high power fields and many apoptotic bodies were also present. No marked cytologic atypia, no necrosis nor perineural or vascular invasion were identified. Tumor cells were immunohistochemically reactive for Cytokeratin AE1/AE3, 7, 18 and 19 and Vimentin. Epithelial membrane antigen (EMA) and S100 protein also showed a week staining. The cells were negative for α-foetoprotein, smooth muscle antigen (SMA), glial acid fibrillary protein (GFAP) and Cytokeratin 20. The Ki67 index was approximately 30% (Fig. 7).

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Fig. 5. Gross findings: the tumor was firm, multilobulated, orange or beige, without necrosis.

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Fig. 6. Microscopic features (hematoxylin eosin saffron×25): Islands and nests of epithelial cells with basaloid appearance separated by bands of fibrous stroma.

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Fig. 7. Immunohistochemical study: Ki67 expression is around 20–30%, mostly in periphery of the nests.

The postoperative course was uneventful and the baby was discharged 1 week after surgery. No adjuvant therapy was undertaken. The patient was seen in follow up 1 month after surgery and then every 2 months. The child is doing well with no clinical evidence of recurrence and no facial palsy 10 months after surgical resection. Recently, 12 months post-operatively, a systematic MRI was done showing no radiological signs of recurrence.

3. Discussion 

Sialoblastomas are rare epithelial tumors affecting the major salivary glands. Among the 31 cases reported in the literature, 25 were found to arise from the parotid gland [2], [3], [4], the remainder in the submandibular gland [3], [5].

Clinically, sialoblastomas usually present as a hard, mobile swelling without any mass effect or skin lesion as in our patient. However there was one case where the skin was red violaceous and another report where there was an important cutaneous ulceration. They can either be detected antenatally by ultrasonography, or discovered at birth; in few cases, it appeared within 2 years after birth [4].

The commonest congenital lesion in the salivary glands with predilection of the parotids is the hemangioma. In our case, antenatal ultrasonography and foetal MRI had many of the characteristics of Rapid Involutive Congenital Hemangioma (RICH) with an important hypervascularity. However hemangiomas typically show tissular hypervascularity with tortuous aspect of the intralesionnal vessels [6]. In our case Doppler ultrasonography showed an important feeding artery but not the typical tissular hypervascularity, even though MRI showed a confusing uniform and rather intense enhancement post-contrast injection. One of the differential diagnoses of congenital hemangioma is congenital fibrosarcoma that can have similar presentation [7]. On MRI, sialoblastoma is usually isointense to muscle on T1-weighted images and shows higher intermediate signal intensity on T2-weighted images. There is a rather weak enhancement after injection of contrast material [4], [8].

Biopsy allows excluding malignancy when all the clinical and radiological criterias for hemangiomas are not met, and to diagnose other perinatal parotid or submandibular tumors. These include the very rare adult-type pleiomorphic and monomorphic adenomas, hamartomatous tumors, malignant salivary glands tumors, but also tumors arising from adjacent tissues like teratomas or congenital sarcomas [1].

Histological diagnosis is based on H&E findings that are corroborated by immunohistochemistry. H&E-stained slides show islands and nests of epithelial cells with basaloid appearance separated by bands of fibrous stroma [2], [3].

Prognostic criterias have been determined by Williams et al. [3], allowing classifying sialoblastomas in two groups: favourable and unfavourable. In our case, the favourable histologic features where the circumscription of the tumor, and the absence of unfavourable features such as anaplasia, neurovascular invasion or necrosis. However, the mitotic rate of 10 per 10hpf and Ki67 index of 30% (proliferative factor) appears to be rather an unfavourable histological feature.

Because of their rarity, the evolution of sialoblastoma is not well known, but there has been a report wherein the tumor became more anaplastic with time (higher mitotic rate and nuclear pleiomorphism) [2]. Moreover, even if they are extremely rare, distant metastases have also been reported [9].

There is no uniform approach to management of sialoblastoma in the literature. Early surgical therapy is the mainstay for the treatment of these tumors and complete excision with negative margins seems to be curative [5], [10]. However, as recurrences have been reported as late as 4 years after excision, the follow up has to be frequent and prolonged [3]. Our patient is examined every 2 months and will have an MRI at one year postoperatively to detect infraclinical recurrence. Chemotherapy has been recommended where the tumor is not completely resectable or with persistent or recurrent tumor [9], [11]. Protocols are usually based on the predicted chemosensitivity of other mesenchymal tumors. Irradiation is considered if the lesions are not completely resectable but the adverse effects of radiotherapy on the growing facial structures can be very profound.

4. Conclusion 

Sialoblastomas are very rare congenital tumors of salivary gland, mainly parotid, origin. They are locally aggressive with a high recurrence rate needing a prolonged follow up. When they are completely resectable, surgery is the mainstay for treatment of these tumors and no adjuvant therapy is needed.