Diagnostic clues and pitfalls in salivary gland fine-needle aspiration cytology

Salivary gland tumors (SGT) display morphological diversity and pose diagnostic challenges. Preoperative fine needle aspiration cytology (FNAC) is a minimally invasive and efficient diagnostic test. However, due to the limited sample size, the final diagnosis may not be established based on FNAC alone. Although cytomorphology and architecture are usually preserved on FNAC, morphologic changes specific to FNAC can complicate the diagnosis. The Milan System for Reporting Salivary Gland Cytopathology categorizes complex FNAC interpretations. Because the cytological diagnosis is closely linked to the histological diagnosis, a multidimensional approach considering the possibility of several differential diagnoses is necessary. From the standpoint of treatment, distinguishing high-grade malignancy from low-grade malignancy is more important than distinguishing malignancy from benign tumors.

Deep learning based ultrasound analysis facilitates precise distinction between parotid pleomorphic adenoma and Warthin tumor

Background

Pleomorphic adenoma (PA), often with the benign-like imaging appearances similar to Warthin tumor (WT), however, is a potentially malignant tumor with a high recurrence rate. It is worse that pathological fine-needle aspiration cytology (FNAC) is difficult to distinguish PA and WT for inexperienced pathologists. This study employed deep learning (DL) technology, which effectively utilized ultrasound images, to provide a reliable approach for discriminating PA from WT.

Methods

488 surgically confirmed patients, including 266 with PA and 222 with WT, were enrolled in this study. Two experienced ultrasound physicians independently evaluated all images to differentiate between PA and WT. The diagnostic performance of preoperative FNAC was also evaluated. During the DL study, all ultrasound images were randomly divided into training (70%), validation (20%), and test (10%) sets. Furthermore, ultrasound images that could not be diagnosed by FNAC were also randomly allocated to training (60%), validation (20%), and test (20%) sets. Five DL models were developed to classify ultrasound images as PA or WT. The robustness of these models was assessed using five-fold cross-validation. The Gradient-weighted Class Activation Mapping (Grad-CAM) technique was employed to visualize the region of interest in the DL models.

Results

In Grad-CAM analysis, the DL models accurately identified the mass as the region of interest. The area under the receiver operating characteristic curve (AUROC) of the two ultrasound physicians were 0.351 and 0.598, and FNAC achieved an AUROC of only 0.721. Meanwhile, for DL models, the AUROC value for discriminating between PA and WT in the test set was from 0.828 to 0.908. ResNet50 demonstrated the optimal performance with an AUROC of 0.908, an accuracy of 0.833, a sensitivity of 0.736, and a specificity of 0.904. In the test set of cases that FNAC failed to provide a diagnosis, DenseNet121 demonstrated the optimal performance with an AUROC of 0.897, an accuracy of 0.806, a sensitivity of 0.789, and a specificity of 0.824.

Conclusion

For the discrimination of PA and WT, DL models are superior to ultrasound and FNAC, thereby facilitating surgeons in making informed decisions regarding the most appropriate surgical approach.

Clinical parameters predictors of malignant transformation of recurrent parotid pleomorphic adenoma

Malignant transformation (MT) in recurrent parotid pleomorphic adenomas (PAs) is rare; therefore its occurrence lacks reliable predictive factors. Our goal was to clarify the predictors for MT of recurrent parotid PAs based on preoperative clinical parameters. Patients with a clinical diagnosis of recurrent parotid PA were retrospectively enrolled. The association between clinicopathologic variables and MT of PA was assessed using univariate and multivariate analyses. MT occurred in 11.8% of the 467 patients. In univariate analysis, three or more previous recurrences, newly developed facial nerve paralysis, difficulty in mouth opening, tumors with the largest tumor diameter ≥ 2.4 cm, and abnormal neck lymph node enlargement were associated with MT occurrence. Further, multivariate analysis showed that three or more previous recurrences, newly developed facial nerve paralysis, difficulty in mouth opening, and abnormal neck lymph node enlargement were independently related to MT. MT of recurrent PA was not uncommon. Clinical signs of malignancy included newly developed facial nerve paralysis, difficulty in mouth opening, three or more previous recurrences, and abnormal neck lymph node enlargement.

Carcinoma Ex Pleomorphic Adenomas: An Institutional Experience and Literature Review

OBJECTIVES

To provide an institutional experience with cases diagnosed as carcinoma ex pleomorphic adenoma (CXPA), including the cytologic and histologic findings and clinical follow-up, followed by a comparison to the experience documented in the literature.

METHODS

We identified cases of CXPA diagnosed at our institution from 2011 to 2021 and reviewed the cytologic and histologic diagnoses, as well as the treatment and clinical outcomes. Additionally, a literature review of the English literature was performed on CXPAs from 2011 to 2021.

RESULTS

Forty-one cases of CXPA were identified, with the majority subclassified as adenocarcinoma, not otherwise specified. Five tumors underwent cytogenetic studies and five underwent molecular studies. To date, 36 patients are alive, 8 of whom experienced locoregional recurrence or distant metastasis.

CONCLUSIONS

Our institutional experience was comparable to that reported in the literature. Further studies are required to inquire about the role of molecular profiles of CXPAs in clinical risk assessment.

Carcinoma ex-pleomorphic adenoma of mandible: A case report and review of literature

Introduction and importance

The most common benign neoplasm of major and minor salivary glands is pleomorphic adenoma (PA). Around 80 % of all parotid neoplasms are pleomorphic adenomas, while 44–68 % and 38–43 % tumors were pleomorphic adenomas of submandibular and minor salivary gland tumors. PA has been reported in a variety of anatomic locations including true intraosseous mandibular tumor, external ear canal, TMJ region, lacrimal gland, epiglottis, larynx and nasopharynx, breast, lung, esophagus, sinonasal and skull base and trachea.

Pleomorphic adenoma has a tendency to transform into a number of malignancies; carcinoma ex-pleomorphic adenoma, carcinosarcoma or metastasizing pleomorphic adenoma. Pleomorphic adenomas most commonly transform into carcinoma ex-pleomorphic adenoma (CEPA).

Case presentation

A 30-year-old male presented with the primary complaint of a long-standing swelling at his right mandibular region for past 18 months. On intra oral examination, there was a non-healing alveolar socket of right lower 3rd molar tooth while rest of the dentition and mucosal surfaces were normal. On extra oral examination, mouth opening was adequate with intact lower border of the mandible and no palpable lymph nodes in the neck. Initial biopsy of lesion showed pleomorphic adenoma, but later the lesion came out to be carcinoma ex-pleomorphic adenoma, for which he underwent segmental mandibulectomy and free fibular flap.

Clinical discussion

The prevalence of CEPA transformation from pleomorphic adenoma is 1.5 % within the first 5 years of diagnosis, going up to 10 % after 15 years. The true rate of malignant transformation in recurrent pleomorphic adenoma is reported to be 3.3 %. We report a case of an intra-osseous carcinoma ex pleomorphic adenoma (CEPA) of the mandible. It is thought that ectopic entrapment of salivary tissue or developmentally included embryonic remnants of submandibular glands within recesses or lacunae of the mandibular bone could explain the intraosseous origin of a salivary gland tumor in the mandible. Since carcinoma ex pleomorphic adenoma (CEPA) arises from primary or recurrent pleomorphic adenoma, therefore it poses a diagnostic challenge for histopathologists. The radiographic picture of primary tumor/recurrence can mimic odontogenic cyst/tumor; therefore, a sinister disease process should always be kept in mind. In the post operative period, regular follow up is required to treat any recurrence. The recurrence rate for such disease has not been documented.

Conclusion

Intra osseous CEPA is a very rare tumor. Intra bony tumors which rapidly increase in size have signs and symptoms of nerve involvement and cause bony destruction should have a high suspicion of index of malignancy. Therefore, biopsy must be correlated with clinical and radiological features. Regular follow up is necessary to detect any recurrence promptly.

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Carcinoma expleomorphic adenoma is a salivary gland tumor that can rarely occur in unique sites like mandible.

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Pleomorphic adenoma can co-exist with carcinoma expleomorphic adenoma which may give different biopsy results.

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Clinical and radiological correlation with tissue diagnosis is important.

Salivary duct carcinoma: A report of 70 FNA cases and review of the literature

BACKGROUND

Although usually recognized as malignant, fine-needle aspiration (FNA) biopsy of salivary duct carcinoma (SDC) has been confused with other primary salivary gland (SG) neoplasms. This article undertook an analysis of a large collection of SDC FNA cases to assess diagnostic accuracy, specificity, and cytopathology.

METHODS

Cytopathology files were searched for SDC with histopathologic validation. FNA biopsy smears were performed using standard techniques.

RESULTS

Seventy cases from 56 patients (M:F, 1.9:1; age range, 26-92 years; mean age, 65 years) met inclusion criteria. All had tissue confirmation of SDC. FNA sites included: parotid gland (42, 60% cases), neck (10), submandibular gland (7), pre-/post-auricular area (5), face/cheek (3), mediastinal lymph nodes (2), and clavicle (1). Aspirates were from primary (52, 74%), metastatic (12, 17%), and locally recurrent (6, 9%) neoplasms. FNA diagnoses included: SDC (19, 27%), favor/suspicious for SDC (7, 10%), high-grade carcinoma (11), adenocarcinoma (9), carcinoma (6), malignant (6), SG neoplasm (5), atypia (3), SDC versus another malignancy (2), and pleomorphic adenoma (2). Large polygonal cells in groups and single forms showed cribriforming, variable necrosis, pseudopapillae, and oncocytic change. Androgen receptor staining was positive in all cases.

CONCLUSIONS

FNA biopsy is accurate and reliable in classifying SDC as a malignant neoplasm, but much less so for identification as a specific tumor type. Using the Milan system, 86% of aspirates were classified as either malignant or suspicious for malignancy. A recurring pitfall includes sampling error in cases of SDC ex pleomorphic adenoma.

Glial Fibrillary Acidic Protein Expression Helps Distinguish Pleomorphic Adenoma from Histologic Mimics

Pleomorphic adenoma (PA) is the most common biphasic type of salivary gland tumour to arise in adults. It is a biphasic tumour composed of both luminal (ductal) cells and abluminal (basal and myoepithelial) cells. Other biphasic salivary gland type tumours, both benign and malignant, can mimic PA, especially on small biopsies. Previous studies have shown that glial fibrillary acidic protein (GFAP) is preferentially expressed in PA and can be useful in the distinction from other salivary gland tumours. However, most of these studies were performed on a small subset of tumour types at a time when the classification of salivary gland type tumours was less refined. The purpose of this study was to assess the expression of glial fibrillary acidic protein (GFAP) in a broad group of both benign and malignant salivary gland tumours. The expression of GFAP was assessed in 99 tumours including 54 PAs, 5 basal cell adenomas, 1 myoepitheliomas, 5 adenoid cystic carcinomas, 6 epithelial-myoepithelial carcinomas (EMCA), 6 mucoepidermoid carcinomas, 7 salivary duct carcinomas, 1 adenocarcinomas NOS, 2 myoepithelial carcinomas, 4 basal cell adenocarcinomas, 5 acinic cell carcinomas and 3 polymorphous adenocarcinomas. Of the malignant cases, 8 were classified as carcinomas ex PA. GFAP was also assessed in 19 concurrent biopsy specimens. GFAP was expressed in the resections of 51 PAs examined (94%). Expression was predominantly strong and diffusely seen in myoepithelial cells. Strong and diffuse GFAP expression was also seen in two EMCAs (33%) and one myoepithelial carcinoma (50%). On biopsy specimens, 100% of PAs and basal cell adenomas expressed GFAP. GFAP was also seen in 1 out of 3 carcinomas ex PAs on biopsies. Almost all PAs show strong and diffuse expression of GFAP. In contrast, most malignant neoplasms that can mimic PA on biopsies show only rare, focal expression. Other benign tumours composed of abluminal/myoepithelial cells also show focal expression of GFAP, highlighting the spectrum these tumours share with PA. Overall, the presence of strong and diffuse GFAP expression can favour a benign neoplasm, specifically a PA, on limited biopsy specimens.

Salivary duct carcinoma: Updates in histology, cytology, molecular biology, and treatment

Salivary duct carcinoma (SDC) is an aggressive subtype of primary salivary gland carcinoma, often with an advanced stage at presentation and high rates of metastasis and recurrence. It most commonly arises in the parotid gland of older men and microscopically resembles high-grade breast ductal carcinoma. While 50 years have lapsed since the first report of this entity, recent intensive studies have shed light on its biologic, genetic, and clinical characteristics. The diagnosis of SDC is aided by the immunohistochemical expression of androgen receptor (AR) coupled with its characteristic histomorphology. Fine-needle aspiration typically reveals cytologic features of high-grade carcinoma, and ancillary studies using cell block material can facilitate the specific diagnosis of SDC. In surgical specimens, certain histologic features are important prognostic factors, including nuclear pleomorphism, mitotic counts, vascular invasion, and the morphology at the invasion front. Several clinical studies have shown promising results using targeted therapy for AR and human epidermal growth factor receptor 2 (HER2), and the latest version of the National Comprehensive Cancer Network guidelines recommends the evaluation of AR and HER2 status before treatment. Recent molecular analyses have revealed multiple heterogeneous alterations in well-known oncogenes and tumor suppressor genes, including TP53, HRAS, PIK3CA, PTEN, and BRAF. Clinical trials of drugs targeting these genes may broaden the treatment options for SDC in the near future.

Spontaneous infarction of pleomorphic adenoma of the parotid gland: A case report

Infarction after the fine-needle aspiration (FNA) procedure is a well-recognized phenomenon of salivary gland lesions. Though extremely rare, spontaneous infarction without previous FNA can occur in pleomorphic adenoma (PA). The present report describes a fourth cytological case of spontaneous infarction of PA of the parotid gland using immunocytochemical analysis, to the best of our knowledge, for the first time. A 57-year-old Japanese female presented with persistent swelling of the right neck region. Physical examination revealed a tumour in the right parotid gland, and FNA examination of the tumour was performed following surgical resection. The Papanicolaou smear demonstrated the presence of fully necrotic cell clusters of varying sizes in a necrotic background. Only a few viable cell clusters were observed. These cells were polygonal to spindle-shaped, and exhibited large round to oval nuclei with a conspicuous nucleoli. Although nuclear pleomorphism was noted, the nuclear chromatin was fine. No neoplastic myoepithelial cells were observed. Therefore, it was suspected that these cells were malignant. Immunocytochemical analysis indicated that these atypical cells were positive for p40. Histopathological examination of the resected parotid gland tumour revealed infarcted PA. Our study revealed that the presence of atypical squamous metaplastic cells in a necrotic background was a characteristic cytological feature of infarcted PA, and that these atypical squamous cells can have large nuclei with conspicuous nucleoli and exhibit pleomorphism. Although cytological diagnosis of infarcted PA is difficult, pathologists and cytopathologists must consider the presence of atypical metaplastic squamous cells in benign salivary gland tumours, including infarcted PA.

Prominent oncocytic metaplasia in pleomorphic adenoma: A potential diagnostic pitfall

Pleomorphic adenoma (PA) is the most common salivary gland tumor. The cytological features of PA are well recognized, and its diagnosis is straightforward in most cases. Some metaplastic changes in PA are well known; however, occurrence of oncocytic metaplasia in PA is very rare. In this report, we describe the first cytological case of prominent oncocytic metaplasia in PA identified based on immunocytochemical analysis. We report the case of a 62-year-old Japanese female who presented with swelling of the left neck region. A fine-needle aspiration cytologic examination was performed followed by surgical resection. The Papanicolaou smear revealed the presence of discohesive neoplastic cells in a myxoid background. These neoplastic cells had a relatively rich, granular cytoplasm, and round nuclei with moderate pleomorphism. Initial cytodiagnosis revealed carcinoma ex PA (CXPA). Immunocytochemical analysis showed that abundant mitochondria were present in the cytoplasm of these neoplastic cells. Histopathological examination of the resected tumor demonstrated proliferation of oncocytic neoplastic cells within a myxoid material and the presence of conventional PA components. A final diagnosis of prominent oncocytic metaplasia in PA was made. Oncocytic metaplasia showed nuclear atypia and pleomorphism; therefore, CXPA, which presents with severe nuclear atypia and necrotic background, must be differentiated from oncocytic metaplastic PA. Recognition of oncocytic metaplasia in PA is important for correct diagnosis.