Grayson G. Cole

Purpose: Salivary duct carcinoma (SDC) is the most common malignancy to arise in a pleomorphic adenoma (PA). Intracapsular or non-invasive carcinoma ex PA (CXPA) is defined by the presence of malignant-appearing tumor cells within the PA that do not violate the tumor border. Knowledge regarding the possible morphologic spectrum and prognosis of intratumoral CXPA is scarce. This study aims to evaluate the morphologic, immunohistochemical, and clinical features of PAs with apocrine / salivary-duct-like intratumoral atypia. Methods: Surgical pathology databases were queried for in situ or intracapsular/intratumoral SDC ex PAs and PAs with atypical epithelial cells (AEC). Exclusion criteria included recurrent lesions, invasion, positive margins, atypia only in myoepithelial cells, or other morphologic variants. Chromogenic multiplex (androgen receptor (AR) and HER2) and monoplex (p40) assays were performed on all available cases, as well as on a control group of non-atypical benign PAs and overtly invasive SDCs. Clinical outcomes were recorded. Results: 96 cases were identified: 23 AEC, 6 apocrine metaplasia, 41 benign PA, 8 SDC ex PA. All AEC, apocrine metaplasia, and benign cases were treated with surgery alone, with 3 AEC cases also receiving a neck dissection. No case recurred. Five of 8 SDC ex PA recurred; 3 died of disease. AR and HER2 were respectively expressed in 96% and 22–48% of AEC; 83% and 0% of apocrine metaplasia; 51% and 0% of benign PA; and 86–100% and 38–57% of SDC ex PA. Patients had increasing average age from benign (~ 50 years) to atypical/in situ (60 years) to invasive carcinoma (~ 70 years). Conclusion: The presence of epithelial atypia within a PA (ranging from isolated AR expression to apocrine metaplasia to overtly dysplastic/malignant epithelial cells) does not portend recurrence or metastasis if the atypia is confined within the borders of the adenoma and negative margins are achieved. Therefore, use of the term “in situ/intracapsular/intratumoral salivary duct carcinoma ex pleomorphic adenoma” is discouraged in light of good prognosis and potential for overtreatment by clinical teams. Nomenclature such as pleomorphic adenoma with epithelial “atypia” or “dysplasia” is recommended, followed by a comment regarding the morphologic features and likely indolent behavior.

Adenoid cystic carcinoma arising in the external auditory canal is rare, and even rarer are cases with sebaceous differentiation mimicking sebaceous carcinoma. This case with clinical, radiologic, gross, and histologic images exemplifies an unusual occurrence of adenoid cystic carcinoma in the external auditory canal with sebaceous differentiation, confirmed by MYB::NFIB fusion.

Background Acinic cell carcinoma (AciCC) is the second most common pediatric malignant salivary gland tumor. However, there are limited pathology publications about this tumor in the pediatric population. Methods We describe four pediatric AciCC cases diagnosed between 2000 and 2021 in our institute. Reticulin histochemistry plus immunohistochemistry for NR4A3 and DOG1 were performed on all cases. Results Histologically, all four cases featured a tumor-associated lymphoid proliferation and collagenous stroma, in which two formed central scars. The tumors were predominantly solid, with a lobular pattern and variably sized dilated spaces, including one case with focal microcysts. High-grade transformation was not observed in any of our cases. Reticulin stain and immunohistochemistry for NR4A3 showed distinct features between AciCC and non-neoplastic salivary gland parenchyma. DOG1 immunohistochemistry confirmed the acinar origin of AciCC. Conclusions Our study reveals that pediatric AciCCs often present with tumor-associated lymphoid proliferation (TALP) and sclerosis. Special stains such as reticulin histochemistry and NR4A3 immunohistochemistry are helpful to separate tumor from adjacent benign parenchyma. The ancillary study is helpful for the diagnosis of small specimens. Our study is limited by its low case number, but we hope that our results will promote more studies on this rare salivary gland tumor in the pediatric population.

Primary osteosarcomas of the jaw (OSJ) are rare, accounting for 6% of all osteosarcomas. This study aims to determine the value of SATB2 and MDM2 immunohistochemistry (IHC) in differentiating OSJ from other jawbone mimickers, such as benign fibro-osseous lesions (BFOLs) of the jaw or Ewing sarcoma of the jaw. Certain subsets of osteosarcoma harbor a supernumerary ring and/or giant marker chromosomes with amplification of the 12q13–15 region, including the murine double-minute type 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) genes. Special AT-rich sequence-binding protein 2 (SATB2) is an immunophenotypic marker for osteoblastic differentiation. Cases of OSJ, BFOLs (ossifying fibroma and fibrous dysplasia) of the jaw, and Ewing sarcoma of the jaw were retrieved from the Departments of Oral Pathology and Oral Medicine, Faculty of Dentistry, Obafemi Awolowo University and Lagos State University College of Medicine, Nigeria. All OSJ retrieved showed histologic features of high-grade osteosarcoma. IHC for SATB2 (clone EP281) and MDM2 (clone IF2), as well as fluorescence in situ hybridization (FISH) for MDM2 amplification, were performed on all cases. SATB2 was expressed in a strong intensity and diffuse staining pattern in all cases (11 OSJ, including a small-cell variant, 7 ossifying fibromas, and 5 fibrous dysplasias) except in Ewing sarcoma, where it was negative in neoplastic cells. MDM2 was expressed in a weak to moderate intensity and scattered focal to limited diffuse staining pattern in 27% (3/11) of cases of OSJ and negative in all BFOLs and the Ewing sarcoma. MDM2 amplification was negative by FISH in interpretable cases. In conclusion, the three cases of high-grade OSJs that expressed MDM2 may have undergone transformation from a low-grade osteosarcoma (LGOS). SATB2 is not a dependable diagnostic marker to differentiate OSJ from BFOLs of the jaw; however, it could serve as a valuable diagnostic marker in differentiating the small-cell variant of OSJ from Ewing sarcoma of the jaw, while MDM2 may be a useful diagnostic marker in differentiating OSJ from BFOLs of the jaw, especially in the case of an LGOS or high-grade transformed osteosarcoma.