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Myoepithelial carcinoma (MECA) is a rare salivary gland (SG) neoplasm (0.1–0.45% of all SG tumors) that often presents with bland cytomorphology and can be misclassified as cellular pleomorphic adenoma (PA) or myoepithelioma. This is particularly challenging in MECA ex-PA cases, especially if tumor shows minimal to no capsular invasion. We report a rare case of a 76-year-old female; history of left superficial parotidectomy with diagnosis (outside hospital) of cellular PA, who re-presented 9 months post surgery with enlarging left parotid mass, neck lymphadenopathy and facial nerve deficits. FNAB of parotid and neck lymph node revealed cellular aspirates with loosely cohesive clusters of myoepithelial cells with occasional chondromyxoid stroma. Prior resection slides were reviewed, and diagnosis of MECA ex-PA was made. Patient underwent left radical parotidectomy, selective neck dissection, with facial nerve sacrifice (due to extensive encasing by tumor). Histology showed a multinodular tumor with pushing borders, zonal arrangement comprising of a hypocellular, necrotic/myxoid center, and a peripheral rim of myoepithelial cells, confirmed by positive S100, and p63. Tumor extensively infiltrated peri parotid soft tissues with multiple foci of lymphovascular and perineural invasion; and metastatic neck lymph nodes. Next generation sequencing revealed a novel TERT promoter mutation (c.-124C > T), not usually described in SG neoplasms. Further, PD-L1 immunohistochemistry showed positive expression, making patient eligible for anti-PDL-1 immunotherapy. This case highlights importance of recognizing the subtle malignant features of MECA in distinguishing it from benign mimics like PA. In addition, presence of TERT mutation opens a new arena for future research to explore potential treatment targets.

PLAG1 rearrangements have been described as a molecular hallmark of salivary gland pleomorphic adenoma (PA), carcinoma ex pleomorphic adenoma (CEPA), and myoepithelial carcinoma (MECA). Several fusion partners have been described, however, commonly no further assignment to the afore mentioned entities or a morphological prediction can be made based on the knowledge of the fusion partner alone. In contrast, TGFBR3-PLAG1 fusion has been specifically described and characterized as an oncogenic driver in MECA, and less common in MECA ex PA. Here, we describe the clinicopathological features of three TGFBR3-PLAG1 fusion positive salivary gland neoplasms, all of which arose in the deep lobe of the parotid gland. Histopathology showed high morphological similarities, encompassing encapsulation, a polylobular growth pattern, bland basaloid and oncocytoid cells with myoepithelial differentiation, and a distinct sclerotic background. All cases showed at least limited, unusual foci of minimal invasion into adjacent salivary gland tissue, including one case with ERBB2 (Her2/neu) amplified, TP53 mutated high-grade transformation and lymph node metastases. Of note, all cases illustrated focal ductal differentiation. Classification remains difficult, as morphological overlaps between myoepithelial-rich cellular pleomorphic adenoma, myoepithelioma and myoepithelial carcinoma were observed. However, evidence of minimal invasion advocates classification as low-grade myoepithelial carcinoma. This case series further characterizes the spectrum of uncommon cellular myoepithelial neoplasms harboring TGFBR3-PLAG1 fusion, which show recurrent minimal invasion of the adjacent salivary gland tissue, a predilection to the deep lobe of the parotid gland and potential high-grade transformation. This article is protected by copyright. All rights reserved. Keywords: (MeSH): Salivary gland neoplasms; adenoma; parotid gland; pleomorphic; transforming growth factor beta.

Basaloid tumors are a common diagnostic problem in salivary gland pathology. However, delineating each of these tumor types is facilitated by an algorithmic approach incorporated by tumor border and cell types. This approach greatly diminishes the challenge of separating polymorphous low-grade adenocarcinoma (PLGA) from adenoid cystic carcinoma (ACC). Despite the overlap in growth pattern, ACC is biphasic while PLGA is not. More relevant challenges, namely differentiation of the biphasic basaloid neoplasms including: epithelial-myoepithelial carcinoma (EMCA), cellular pleomorphic adenoma (PA), basal cell adenoma (BCA), and basal cell adenocarcinoma (BCAC), are resolved by a combination of morphologic, immunophenotypic, and to a limited extent, molecular features. Among the most challenging scenarios is high-grade transformation of any of the aforementioned entities. Here, the diagnosis requires recognition of a conventional component and exclusion of metastatic (or in some cases primary) SCC and even select neuroendocrine carcinomas and sarcomas in some cases.

Membranous basal cell adenoma (MBCA) is a rare benign salivary gland neoplasm. It is difficult to diagnose MBCA based on fine-needle aspiration (FNA) cytology due to rare reporting of its FNA cytology and overlapping of its FNA cytologic features with some benign and malignant entities. We present a case of MBCA in a 67-year-old female that was originally misinterpreted as adenoid cystic carcinoma (ACC) on FNA cytology. The FNA smears showed numerous uniform small basaloid epithelial cells with round or oval nuclei and inconspicuous nucleoli, and scant cytoplasm. The basaloid cells surround acellular, dense, homogenous material or are surrounded by acellular or paucicellular dense homogeneous material possibly containing bland spindle cells. The basaloid cells are present in variably sized three-dimensional clusters, acini, or sheets with variable cohesion. The dense homogenous material surrounded by basaloid cells may be interconnected. High power magnification reveals the homogeneous material to have a fibrillar texture. The edges of dense homogenous materials were well-demarcated. We describe the diagnostic pitfalls of FNA for MBCA, particularly versus ACC, basal cell adenoma, cellular pleomorphic adenoma, myoepithelioma, basal cell adenocarcinoma, and basaloid squamous cell carcinoma in hope of improving clinical management and patient treatment.

Basal cell adenoma (BCA) is a rare neoplasm which is one of the basaloid tumors of salivary gland. Basaloid tumors are the most difficult problem in salivary gland fine needle aspiration cytology (FNAC). There are various benign and malignant tumors such as; cellular pleomorphic adenoma, basal cell adenocarcinoma, adenoid cystic carcinoma, metastatic basal cell carcinoma, metastatic basaloid squamous carcinoma and small cell carcinoma in differential diagnosis. We present a case of BCA, membranous type in a 39-year-old female with right submandibular swelling misinterpreted as adenoid cystic carcinoma (ACC) on FNAC.

Basal cell adenoma (BCA) is a rare benign basaloid neoplasm of the salivary gland. There are four histopathological types of BCA: solid, tubular, trabecular, and membranous. It is known that focal squamous metaplasia may be seen in some BCAs, but it is rare to see extensive squamous metaplasia, especially with cellular atypia. Here, a 25-year-old male with right parotid swelling is presented. Ultrasonography revealed a 2-cm well defined mass in his parotid gland. Fine-needle aspiration (FNA), performed prior to surgical excision, showed a highly cellular tumor composed of basaloid cells, forming small duct-like or tubular structures containing basement membrane-like material, as well as squamous cells with hyperchromatic, enlarged, pleomorphic, and bizzare nuclei. We made a cytopathological diagnosis of "basaloid neoplasm" and also reported that the differential diagnosis included BCA, cellular pleomorphic adenoma, basal cell adenocarcinoma, and carcinoma ex pleomorphic adenoma. The patient underwent total parotidectomy. Both frozen and permanent sections showed a BCA with membranous, tubulotrabecular pattern, and extensive squamous metaplasia. Some of the squamous cells showed significant nuclear hyperchromasia, enlargement, and pleomorphism. As far as we know, this is the first case of BCA with extensive squamous metaplasia and prominent cellular atypia. This case has been presented to show that squamous metaplastic cells with hyperchromatic, enlarged, bizarre, and pleomorphic nuclei can be seen on FNA smears of a benign tumor like BCA. Also, the differential diagnosis of BCA of the salivary gland is discussed here.

Papillary microcarcinoma may present with clinical symptoms, most commonly jugulodigastric and pretracheal lymphadenopathy with or without palpable thyroid nodules. Isolated submandibular metastases are rare. We are presenting here a case report of 40-year old lady with an isolated submandibular gland metastasis arising from a papillary thyroid carcinoma. Submandibular gland excision of right side was done based on the fine needle aspiration cytology (FNAC) which suggested features of Basal cell adenoma vs cellular pleomorphic adenoma. USG neck s/o 3×3.5×2.8 cm sized hypoechoic lesion right submandibular. Histopathologic examination of the specimen suggested a metastatic papillary carcinoma. Total thyroidectomy was done, no other site of metastasis was found on radio-iodine scanning.

OBJECTIVE: To retrospectively assess the diagnostic accuracy, cytologic features and pitfalls of Thin Prep® (TP) (Cytyc Corporation, Marlborough, Massachusetts, U.S.A.) versus conventional (smear) preparation (CP) in salivary gland fine needle aspiration biopsies (FNABs) and second, to evaluate the reproducibility of the cytomorphologic criteria used in the evaluation of FNABs prepared by CP versus TP. STUDY DESIGN: All salivary gland fine needle aspiration biopsies (SGFNABs) between January 1996 and June 1999 were retrieved from the cytology files of the University of Michigan Hospital. Histologic correlation was identified when available. Two cytopathologists reevaluated the slides for artifacts, cellular preservation, background material, cellularity, and cytoplasmic and nuclear details. RESULTS: Seventy-four of the 134 (55%) cases identified had histologic follow-up. Fifty (68%) cases were processed by TP and 24 (32%) by CP. FNAB processed by TP and CP correctly identified malignancy in 14 and 9 cases, respectively. There were three (4%) false negative cases. These included two acinic cell carcinomas and one mucoepidermoid carcinoma. There were 37 true negative cases (24 TP and 13 CP) and one false positive case of cellular pleomorphic adenoma (cytologic interpretation, mucoepidermoid carcinoma). All discrepant cases were processed using the TP method. The overall specificity and sensitivity were 98% and 88%, respectively. However, specificity and sensitivity for TP-processed SGFNABs were 96% and 82% as compared to a 100% specificity and sensitivity for CP. Additionally, there were 10 (14%) nondiagnostic cases, 8 of which were processed by TP. Cytologic artifacts associated with TP included diminished/distorted extracellular and stromal elements, cellular shrinkage and tissue fragmentation CONCLUSION: The diagnostic accuracy of TP-processed SGFNABs approaches that of the CP. However, there are several artifacts that may lead to erroneous diagnoses. Additional studies, that depend on real-life clinical samples processed by TP are suggested to modify current diagnostic criteria.

Herein we present a group of rare tumors of the sella region that have not been previously recognized. Although clinically and radiographically the tumors resemble nonfunctioning pituitary adenomas, their histologic, immunohistochemical, and ultrastructural features differ and indicate a salivary gland origin. The lesions cover a morphologic spectrum that includes cellular pleomorphic adenoma, monomorphic adenoma, oncocytoma, and low-grade adenocarcinoma of the salivary gland. All tumors except the oncocytoma were immunoreactive for cytokeratin and were negative for pituitary hormones and synaptophysin. Ultrastructural characteristics in the cases examined include hypodense stromal material, basal lamina, and tonofilament bundles. The single oncocytoma was packed with mitochondria and lacked membrane-bound secretory granules. DNA ploidy based on image analysis and MIB-1 labeling indices showed diversity within this group of tumors, with labeling indices ranging from 0.06% to 15%. The presumed origin of these rare neoplasms is from salivary gland rests related to the normal pituitary gland. Despite their varied morphology, such tumors are easily confused with pituitary adenoma. Although rare, tumors of salivary gland origin should be considered in the differential diagnosis of unusual adenohypophyseal tumors.

Encapsulated Minimally Invasive Epimyoepithelial Carcinoma of Submandibular Gland - A New Entity?? With Review of Literature Epimyoepithelial carcinoma (EMC) is a rare low-grade salivary gland malignancy comprising of 1% of all the salivary glands tumors. EMC is a rare tumor when involving submandibular gland (8.6%) as compared to parotid gland (62.1%). A thorough pubmed literature search retrieved only 17 cases of EMC involving submandibular gland since 1972. EMC can present in classical pattern characterised by biphasic cell population with inner layer of cuboidal to columnar cells and outer layer of myoepithelial cells. Encapsulated minimally invasive epimyoepithelial carcinoma is a recently coined terminology by Seethala et al. To the best of our knowledge, this is the first case of encapsulated minimally invasive EMC of submandibular salivary gland discussed in the literature. The present paper highlights the review of literature of EMC involving submandibular salivary gland, histomorphological spectrum and diagnostic differentiation from other salivary gland tumors.

Pleomorphic adenoma, the most common salivary gland tumor, accounts for 54 to 65% of all salivary gland neoplasm and 80% of the benign salivary gland tumors. Most frequently it affects the parotid gland, followed by the submandibular and the minor salivary glands. Microscopically, mucous, sebaceous, oncocytic and squamous metaplasia sometimes with the formation of keratin cyst, may be present. Extensive squamous metaplasia can be mistaken for malignancy, including mucoepidermoid carcinoma and squamous cell carcinoma. Here, we present an unusual case of pleomorphic adenoma with presence of extensive squamous metaplasia, keratin cyst formations and dense cluster of basaloid cells with spherical hyaline globules giving rise to suspicion of mucoepidermoid and adenoid cystic carcinoma.

The cytologic features of five cases of epithelial-myoepithelial carcinoma arising in major salivary glands (four parotid and one submandibular gland) are presented. All cases were initially diagnosed as low-grade malignancies. The smears were generally cellular, with no specific architectural pattern. Single cells and naked nuclei were prominent in all cases. A biphasic epithelial (small-cell) and myoepithelial (large/clear-cell) pattern was identified readily in two cases and with difficulty in one case. The biphasic pattern may be subtle or absent since the clear cells have a fragile cytoplasm and often appear as naked nuclei. The differential diagnosis includes adenoid cystic carcinoma, polymorphous low-grade adenocarcinoma, and cellular pleomorphic adenoma.

Basaloid tumors of the salivary glands are a heterogeneous group of benign and malignant lesions characterized by small tumor cells with round or ovoid nuclei surrounded by a thin rim of cytoplasm. Primary salivary gland tumors with this predominant morphology include basal cell adenoma, basal cell adenocarcinoma, cellular pleomorphic adenoma, adenoid cystic carcinoma, and small cell undifferentiated carcinoma. Certain metastatic lesions and nonepithelial neoplasms can also demonstrate a basaloid appearance. Histologic diagnosis based on resected tumors is usually straightforward when the architecture can be adequately assessed. However, in limited biopsies and particularly in cytologic samples, the evaluation can be quite challenging. A systematic approach aided by immunohistochemistry is essential to arrive at an accurate diagnosis.

Objective To study the spectrum of cytologic changes seen in cellular pleomorphic adenoma (CPA) and to determine features that would allow a more specific diagnosis. Study design We reviewed 11 fine needle aspirates of surgically confirmed salivary gland CPA in addition to three discrepant cases in which CPA was strongly considered in the cytologic diagnosis. Results Pleomorphic adenoma was considered in the differential diagnosis, but a difinitive cytologic diagnosis was not made in the 11 cases. Acinic cell carcinoma, basal cell adenoma, adenoid cystic carcinoma; myoepithelioma and spindle cell neoplasm accounted for most of the other diagnostic considerations. The three discrepant cases included a malignant myoepithelioma, acinic cell carcinoma and mucoepidermoid carcinoma. Conclusion Familiarity with the variable aspirate appearance of CPA in addition to well-defined cytologic and architectural criteria can help establish the proper diagnosis in the majority of cases. There remain, however, few cases in which a definitive diagnosis is not possible.

A case of cellular pleomorphic adenoma of the parotid gland was studied by electron microscopy. The tumor contained stromal masses of 8-nm filaments that were identified as amyloid. None of the surrounding cells contained amyloid fibers

The light microscopic, immunohistochemical, and ultrastructural features of a unique variant of tubular-trabecular basal cell adenoma are described. The unusual feature of the six examples reported is the richly cellular "stroma" composed of spindle cells coursing between the anastomosing cords of epithelial tumor cells. Immunohistochemistry of all six cases and electron microscopy of two examples illustrated the biphasic differentiation of the epithelial portion of this form of basal cell adenoma, with a central core of duct luminal cells bordered on either side by one or more layers of modified myoepithelial cells. By light microscopy, the features and arrangement of cells in "stromal" regions of this tumor convey a fibroblastic derivation. However, this population of cells stains strongly for S-100 protein, ultrastructurally displays excessive external lamina production, intercellular junctions, and a growth pattern unlike fibroblasts, and is involved in the formation of extracellular mucinous materials. Such aspects indicate a second population of neoplastic myoepithelial cells in this tumor. Thus, this form of tubular-trabecular basal cell adenoma displays tricellular differentiation and, perhaps, may be considered either a hybrid basal cell adenoma and myoepithelioma or a cellular pleomorphic adenoma.