Sialoblastoma is one of the rare tumors of the salivary gland. It is a congenital
tumor arising most often from the parotid gland. This tumor is also known as basaloid
adenocarcinoma, basal cell adenoma, and congenital basal cell adenoma. It has significant
variability in biologic behavior. It was originally considered a benign tumor, but
locoregional and distant metastasis have been described. Here, we describe a child
with metastatic progressive sialoblastoma.
A 1-year 7-month-old Indian girl presented to us with complaints of swelling of the
left cheek for a year. She was treated with multiple courses of antibiotics, despite
which the swelling persisted. She was noted to have a 5 cm × 6 cm swelling over the
left parotid area. Ultrasound of the parotid region revealed lobulated hypoechoic
lesion in the superior lobe of the left parotid gland. Magnetic resonance imaging
neck showed enlargement of the superficial lobe suggestive of parotid neoplasm. Fine-needle
aspiration cytology was suggestive of rhabdomyosarcoma elsewhere, and she underwent
superficial left parotidectomy. Histopathological evaluation of the specimen was suggestive
of Grade III sialoblastoma with immunohistochemistry positive for S100, vimentin and
patchy staining for EMA. She developed a 6 cm × 8 cm firm swelling in the parotid
area extending from the inferior orbital margin to the mandible and from the angle
of the mouth to the retroauricular region 1 month after surgery [Figure 1]. Fluorodeoxyglucose positron emission tomography–computed tomography (PET CT) scan
revealed multiple lung nodules. She underwent left radical parotidectomy [Figure 2]. Chemotherapy and radiotherapy were offered as treatment options, but parents refused
treatment. PET CT was repeated one-month post surgery. It showed new lesion in the
infratemporal fossa and increase in the size and number of lung lesions. The family
was counseled regarding repeat surgery followed by radiation and chemotherapy; however,
they did not opt for any treatment. She was followed up telephonically for 10 months
postsurgery during which she was doing well. She was lost to follow-up after 10 months.
Figure 1: Preoperative picture showing massive swelling on the left cheek
Figure 2: Postoperative picture showing considerable decrease in the size of the swelling
Sialoblastomas are rare salivary gland tumors usually present at birth or recognized
shortly after birth. Age of presentation is reported from the prenatal period to 4
years.[1] Sitthichaiyakul et al. observed that the median age of diagnosis was 9.8 years.[2] There have also been isolated case reports of sialoblastoma in adults.[1]
The incidence is extremely rare with only single case reports being reported. Choudhary
et al. did a literature search and reported 46 cases from 1966 to 2011.[1] Irace et al. reviewed 62 cases of pediatric sialoblastoma in 2016.[3]
There is no clear consensus regarding the pathogenesis of sialoblastoma. It is thought
to arise from the retained blastemal cells in the salivary gland.[2]
Sialoblastomas usually tend to progress locally, with local recurrences and rarely
metastasize.[2] Irace et al. did a literature review of 62 cases, of which only nine patients had metastatic
disease.[3] In a review by Choudhary et al., 10 cases out of 46 recurred. Most cases recurred within 24 months.[1]
Due to the rare incidence of the tumor, there are no standard treatment protocols.[4] Wang et al. reported three cases of congenital sialoblastomas, which did not recur after surgery
and after a mean follow-up of 34 months. They concluded that surgical resection of
the tumor is the safest modality of treatment.[5] Chemotherapy has also been tried as a treatment modality as this is a very chemosensitive
tumor. Saribeyoglu et al. published a case of recurrent sialoblastoma who was treated with vincristine-, actinomycin
D-, and cyclophosphamide-based chemotherapy. They suggested chemotherapy for unresectable
or recurrent sialoblastoma.[6] Neoadjuvant chemotherapy has also been used with good outcome by Prigent et al.[7] Radiation has also proved beneficial in treatment of sialoblastoma with incomplete
removal.[2]
Conclusion
Sialoblastoma is a rare tumor in the pediatric age group that arises from the salivary
gland. Our case highlights the aggressive nature of the disease with local and distant
metastasis. Surgery remains the cornerstone of treatment with radiation and chemotherapy
considered useful in metastatic disease. However, as there are no standard protocols,
treatment has to be individualized.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
