Background: Mucoepidermoid carcinoma (MEC) is the most common malignant
salivary gland tumor, composed of mucinous, intermediate (clear)
and squamoid cells. The palate is the second most common site after the parotid
gland. Most MECs show recurrent translocations involving MAML2
gene and either CRTC1 (60–80%) or CRTC3 (<6%). In the palate, MEC generally
presents as a deeply infiltrative mass. We describe the morphological and FISH analyses of a palatal MEC presenting as an intraoral squamous
papilloma, which, as far as we know, has never previously been described.
Methods: We report a case of an otherwise healthy 55-year-old man who
complained of a painless oral lesion in the left hard palate since more than
20 years. Clinically, a papillomatous lesion was noticed and a superficial
biopsy was consistent with a squamous papilloma. CT scan showed a palatine
lytic mass and the patient underwent left maxillectomy.
Results: The initial biopsy, performed in an outside institution, was not
available for review. At gross analysis the resection specimen showed a
3.2 cm large left hard palate tumour infiltrating the maxillary bone (palatine
processus and maxillary sinus) and nasal submucosa through the palatine
bone, with a superficial papillomatous component. Histologically, the
hard palate mucosa showed a superficial papillomatous epithelial proliferation
overlying a low grade MEC. Break-apart FISH analysis (ZytoVision
probe) showed a MAML2 gene rearrangement in the two components of
the lesion: both in the deeply infiltrating typical MEC and in the superficial
papillomatous component.
Conclusions: The present case illustrates an uncommon feature of palatal
MEC. The presence of a superficial papilloma challenged the adequate classification
of this lesion at first diagnostic approach. FISH analysis finally
demonstrated a clonal relationship between the two observed components,
highlighting that MEC may present clinically as an intraoral papilloma.