Recently, a new subtype of salivary gland cancer (SGC), mammary analogue secretory carcinoma (MASC), has been defined, which is characterized by the presence of ETV6-NTRK3 fusion gene. Previously, MASC was mixed up with acinic cell carcinoma (AciCC), polymorphous low grade adenocarcinoma and (cyst)adenocarcinoma. At present the clinical features and outcome of MASC patients are not well known. We aimed to describe the clinical presentation and outcome of MASC.
Firstly, we re-evaluated the pathological diagnosis of salivary gland cancers with a morphological resemblance to MASC, diagnosed in 4 of the 8 head and neck centres in the Netherlands, for their presence of ETV6-NTRK3 and also included genetically confirmed prospectively diagnosed cases. The ETV6-NTRK3 fusion gene was analyzed using RT-PCR. Secondly, the clinical characteristics were retrieved from the patient files.
Twenty-eight patients with ETV6-NTRK3 fusion gene positive MASC were included (10 prospectively and 18 retrospectively). Of these 18 retrospective patients 13 patients were previously diagnosed as AciCC, the other 5 patients as (low-grade) adenocarcinoma. The median age at diagnosis was 49 years (range 19 – 83 years), 15 patients (54%) were male. The duration of symptoms varied from 6 weeks until 20 years with a median of 14 months. In 18 patients (64%) the tumour was located in the parotid gland; the other patients had tumours of the minor salivary glands (2), submandibular gland (1), oral mucosa/lip (5) or palate (2). All patients had a T1-2 tumour. One patient had lymph node metastasis at diagnosis. All patients underwent surgery of which 4 patients needed re-resection and 12 patients (43%) underwent postoperative radiotherapy. One patient had a local recurrence 50 months after primary surgery, but was cured after second resection. None of the patients had regional recurrences or distant metastases. The median follow-up was 49 months and both the 5- and 10-year overall survival rate were 94%.
MASC is a recently acknowledged new entity of SGC characterized by the ETV6-NTRK3 fusion gene. The clinical course seems to be favourable with a very low rate of recurrences and an excellent survival.
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All authors have declared no conflicts of interest.