Tubulopapillary hidradenoma-like tumor of the mandible

Sialadenoma papilliferum-like intraductal papillary tumour: an emerging entity with intercalated duct differentiation showing MAPK pathway activation in both ductal and myoepithelial cells

Sialadenoma papilliferum-like intraductal papillary tumour (SP-IPT) is a recently described salivary gland tumour that shows identical morphology to sialadenoma papilliferum (SP) except for the lack of an exophytic papillary component. However, the immunohistochemical phenotypes and molecular profiles of SP-IPT remain unclear. This study aims to report new cases of SP-IPT and to determine its cellular differentiation and molecular basis. After histopathological review, four cases of SP-IPT were retrieved. Immunohistochemical staining was performed to analyse the expression patterns of cytokeratin 7 (CK7), p63, smooth muscle actin (SMA), vimentin, S100, mammaglobin, androgen receptor, SOX10, BRAF V600E-mutated protein, and phosphorylated ERK. Sanger sequencing was performed to determine the mutation status of the BRAF, KRAS, NRAS, and HRAS genes. All four cases affected the posterior mandible with a mean age of 62 years and a male-to-female ratio of 3:1. Histologically, all cases consisted of multiple tubular and cystic structures with varying sizes and shapes. The tubulocystic components were lined by a double or few-layered epithelium frequently showing a micropapillary pattern. The outer layer consisted of a rim of myoepithelial cells, which were CK7+/p63+/SMA+/vimentin+/S100+/SOX10+. The inner ductal cells were CK7+/S100+/SOX10+, consistent with intercalated duct differentiation. All cases harboured BRAF V600E mutations, but no other mutations were detected. The BRAF V600E-mutated protein and phosphorylated ERK were expressed in both ductal and myoepithelial cells. These findings demonstrate the immunohistochemical and molecular similarities between SP-IPT and SP and the role and extent of MAPK pathway activation in the pathogenesis of SP-IPT.

Tubulopapillary hidradenoma-like tumor of the mandible: Two case reports of an underrecognized entity

Tubulopapillary hidradenoma-like tumor of the mandible is extremely rare, with only 3 cases published in the English-language literature. The clinicopathological characteristics and histogenesis of this tumor are unclear. Few pathologists and perhaps fewer clinicians are familiar with this entity, and it is likely underrecognized and under-reported. Herein, we present two additional cases, both misdiagnosed as malignancies preoperatively and postoperatively by different unwary pathologists. Awareness and knowledge of this enigmatic entity and its clinical and radiographic features, together with careful morphological assessment should enable the correct diagnosis and prevent unnecessary treatment.

Tubulopapillary Hidradenoma-like Tumour of the Mandible: A Case Report and Literature Review

Tubulopapillary hidradenoma is an uncommon benign sweat gland tumour which appears as a well-defined superficially located dermal nodule, most commonly occurring in the head or of the extremities. Its occurrence is extremely rare in the mandible, as there are only two cases of tubulopapillary hidradenoma-like tumour of the mandiblereported in the literature. Microscopically, the lesion appears as a well circumscribed but unencapsulated neoplasm composed of numerous irregularly shaped tubular structures that have a double to several layered epithelial lining. The outer layer consists of flat to cuboidal myoepithelial cells and inner layer contains cuboidal to columnar cells that demonstrate decapitation secretions. We report an unusual case of tubulopapillary hidradenoma-like tumour presented as a nodular growth in the right retromolar region of the mandible in a 67-year-old man. The light microscopic features along with immunohistochemical findings of this unusual neoplasm are discussed.