Sialadenopapillary ductal tumor: Unifying sialadenoma papilliferum-like intraductal papillary tumor and tubulopapillary hidroadenoma-like tumor of the mandible – Report of an additional case

Sialadenoma papilliferum-like intraductal papillary tumor (SP-IPT) and tubulopapillary hidroadenoma-like tumor of the mandible (TPHLTM) are rare lesions with preferential intraoral involvement and variable clinical behavior. Several studies show that SP, SP-IPT, and TPHLTM share similar morphological features and identical genetic mutations, most commonly BRAF V600E mutation, suggesting close relationship. Recently, a study proposes classifying SP-IPT and TPHLTM under the term "sialadenopapillary ductal tumor" (SDT), which seems to best reflect its clinicopathological spectrum. To date, to the best of our knowledge, about 35 intraoral cases have been reported, which appear to meet histomorphological and/or molecular criteria to be diagnosed as SDT. Although rare, 1 and 2 cases reported nodal metastasis and recurrence, respectively. A 33-year-old patient presented with an asymptomatic nodule on the hard palate. Cone-beam computed tomography revealed a nodular lesion with superficial bone resorption. Microscopy showed a submucosal ductal proliferation, without surface involvement or exophytic component, reminiscent of the inward papillary proliferation of SP. By immunohistochemistry, the luminal component was positive for pan-CK and CK7, whereas the abluminal component was p40, p63, and α-SMA positive. SOX10 highlighted both luminal and abluminal components. The BRAF V600E (VE1) was strongly positive, and the Ki-67 proliferative index was low (<3 %). After 2 months, complete healing was observed. The current case emphasizes that SDT seems to be an appropriate unifying diagnostic term, which can better encompass its variable biological potential.