Oncocytic mucoepidermoid carcinoma (OMEC) is a rare but diagnostically challenging variant of mucoepidermoid carcinoma (MEC). OMEC is notable for differential diagnostic considerations that are raised as a result of overlap with other benign and low-grade oncocytic salivary gland tumors. Diffuse and strong immunoreactivity of p63 protein may be useful in distinguishing OMEC from its mimics. However, focal p63 staining can be present in benign oncytomas. Presence of mucin-containing cells, mucinous cystic formation, and foci of extravasated mucin are considered a hallmark of MEC. True mucocytes may be, however, very few and hardly discernable in OMECs. Recent evidence has shown that most MECs harbor gene fusions involving MAML2. A retrospective review of archived pathology files and the authors’ own files was conducted to search for “low-grade/uncertain oncocytic tumor,” “oncocytoma,” and “oncocytic carcinoma” in the period from 1996 to 2019. The tumors with IHC positivity for p63 and/or p40, and S100 negativity, irrespective of mucicarmine staining, were tested by next-generation sequencing using fusion-detecting panels to detect MAML2 gene rearrangements. Two index cases from consultation practice (A.S. and A.A.) of purely oncocytic low-grade neoplasms without discernible mucinous cells showed a CRTC1-MAML2 fusion using next-generation sequencing, and were reclassified as OMEC. In total, 22 cases of oncocytic tumors, retrieved from the authors’ files, and from the Salivary Gland Tumor Registry, harbored the MAML2 gene rearrangements. Presence of mucocytes, the patterns of p63 and SOX10 immunopositivity, and mucicarmine staining were inconsistent findings. Distinguishing OMEC devoid of true mucinous cells from oncocytoma can be very challenging, but it is critical for proper clinical management. Diffuse and strong positivity for p63 and visualization of hidden mucocytes by mucicarmine staining may be misleading and does not always suffice for correct diagnosis. Our experience suggests that ancillary studies for the detection of MAML2 rearrangement may provide useful evidence in difficult cases.
PurposeAdenoid cystic carcinoma (ACC) is a rare neurotropic cancer with slow progression occurring in salivary glands and less frequently in other body parts. ACC is featured by hyperchromatic nuclei and various mutations in genes encoding chromatin-related machineries. The ACC treatment is mainly limited to the radical surgery and radiotherapy while the chemotherapy remains ineffective. As the knowledge about molecular basis of ACC development is limited, we investigated here the molecular features of this disease.Patients and methodsThis study included 50 patients with ACC. Transcript profiling of available ACC samples vs normal salivary gland tissue, quantitative real-time PCR (qRT-PCR) transcript level measurements and the immunohistochemistry (IHC) for SWI/SNF chromatin remodeling complex (CRC) subunits and androgen receptor on surgery-derived paraffin-embedded samples were performed.ResultsTranscriptomic study followed by Gene Ontology classification indicated alteration of chromatin-related processes, including downregulated transcript levels of main SWI/SNF CRC subunits and elevated expression of BRM ATPase-coding SMARCA2 gene in ACC. Subsequent IHC indicated broad accumulation of BRM ATPase and several SWI/SNF subunits, suggesting affected control of their protein level in ACC. The IHC revealed ectopic, heterogeneous expression of androgen receptor (AR) in some ACC cells.ConclusionsOur study indicated that ACC features aberrant expression of genes controlling chromatin status and structure. We found that the balance between SWI/SNF classes is moved towards the BRM ATPase-containing complex in ACC. As BRM is known to be involved in chemoresistance in cancer cells, this observation may be the likely explanation for ACC chemoresistance.Electronic supplementary materialThe online version of this article (10.1007/s00432-018-2783-5) contains supplementary material, which is available to authorized users.
(1) Background: Biphenotypic sinonasal sarcoma (BSNS) is a rare low-grade neoplasm of the sinonasal tract. It is characterized by specific PAX3 gene rearrangements and both myogenic and neural differentiation. The purpose of the study was to describe the histologic, immunohistochemical and molecular features of BSNS and indicate important clues for small incisional biopsy diagnostics. (2) Methods: Archival samples from patients with nasal cavities or ethmoid sinuses tumors were searched for BSNS cases. Inclusion criteria were the presence of spindle cell morphology and low-grade appearance. Both biopsy and resection specimens were stained for identical IHC panels including, i.a., S100, SMA, SOX10 and PAX3. FISH for PAX3 and SS18 was performed on biopsy specimens. (3) Results: BSNS diagnosis was made in 6 cases included in the study and confirmed by PAX3 rearrangement by FISH in 5 specimens. The pattern of IHC expression was identical for paired biopsy and resection samples apart from one BSNS case. (4) Conclusions: Incisional biopsy seems to be a sufficient method to establish BSNS diagnosis in most cases. Characteristic morphological features together with S100, SOX10 and SMA as the screening markers are useful for confirming the diagnosis. In cases of divergent morphology and immunoprofile evaluation of PAX3 rearrangement is vital.
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