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

Parotid Gland Tumors: Molecular Diagnostic Approaches

Parotid gland pathology represents a web of differential diagnoses. There are many complex cases that require extensive diagnostic tests for a complete and correct final pathology diagnosis. Currently the official classification of parotid gland tumors extends over more than 40 subtypes. We performed a query of the PubMed database regarding the use of molecular biology tests in performing a better characterization of the tumors in specific cases. By using fluorescence in situ hybridization (FISH), reverse transcription polymerase chain reaction (RT-PCR) or next-generation sequencing, the team managing complex cases can offer a personalized therapeutic solution. We review the molecular differential diagnosis according to published articles in the last 5 years for many types of parotid gland tumors ranging from benign to borderline malign tumors to malign aggressive tumors. Mucoepidermoid carcinoma is a distinct subtype of parotid malignancy that was the subject of a consistent number of articles. However, the molecular biology diagnosis techniques helped more in excluding the diagnosis of mucoepidermoid carcinoma, and probably retrospectively limiting the number of cases with this final diagnosis. In Romania, the molecular biology diagnosis is available only in limited research facilities and should receive more consistent funding that will make it available on a larger scale. The novelty of this scoping review is that we propose an algorithm for molecular differential diagnosis of the tumors that could be encountered in the parotid gland.

Molecular testing in salivary gland cytopathology: A practical overview in conjunction with the Milan system

Recently, significant advances in the molecular characterization of salivary gland neoplasms have facilitated the classification and diagnosis of specific diagnostic entities. In the highly challenging diagnostic scenario of salivary malignancies, molecular testing is increasingly being adopted in routine practice to refine the cytological diagnosis of salivary lesions. Here, we reviewed the most recent evidence in the field of salivary glands molecular cytopathology.

Salivary duct carcinoma in the submandibular gland: A rare case report with differential diagnosis

Salivary duct carcinoma (SDC) is a rare and highly aggressive malignant salivary gland neoplasm, accounting for only 0.2% of salivary gland tumours. It predominantly affects the parotid gland and represents a significant concern with limited prevalence (1-1.2 individuals per million). We present a case of a 65-year-old female patient with a clinical history of swelling and pain in the right lower jaw region for six months. Diagnostic investigations revealed a well-defined submandibular gland lesion. Subsequent histopathological and immunohistochemical findings confirmed the lesion to be SDC. This case report emphasises the challenges in diagnosing this aggressive malignancy, which stems from its rarity and resemblance to other neoplasms. It is worth noting that the involvement of the submandibular gland is observed in a mere 12% of SDC cases, while females account for only 25% of the reported instances.

Pitfalls in Salivary Gland Cytology

BACKGROUND

Salivary gland lesions possess diagnostic challenges on fine-needle aspiration (FNA) material. They are relatively uncommon, yet present with a wide spectrum of cytomorphology. Herein, we review common salivary gland neoplasms, their cytomorphologic features, their diagnostic pitfalls, and ancillary studies helpful in achieving an accurate diagnosis.

SUMMARY

There are many cytomorphologic overlaps between benign and malignant salivary gland entities. Moreover, metaplasia, cystic changes, and degenerative changes are common findings adding to diagnostic dilemmas. These complicating factors contribute to a minute risk of malignancy in salivary gland lesions that are interpreted as benign on FNA. In rare cases, even malignant salivary gland neoplasms are misinterpreted as benign on aspirated material due to the many cytomorphologic overlaps. For example, benign and malignant neoplasms containing stroma such as myoepithelioma and adenoid cystic carcinoma may be misinterpreted as pleomorphic adenoma. Moreover, diagnosis of salivary gland neoplasms with basal cell features can be confusing on FNA materials; for example, basal cell adenoma can be misinterpreted as adenoid cystic carcinoma. Mucoepidermoid carcinomas have many different appearances on aspirated material due to variable amounts of mucin, degree of nuclear atypia, cellular content, and squamous metaplasia. Acinic cell carcinoma exhibits large cells with abundant cytoplasm on FNA, which can be mistaken for oncocytic cells in oncocytoma or Warthin tumor. Salivary duct carcinoma shows distinct features of malignancy and thus can be mistaken for secondary tumors involving the salivary glands or other malignant salivary gland tumors. The presence of tumor-associated lymphocytes is another underlying cause of misdiagnosis, especially when considering the differential diagnosis of an intraparotid lymph node. Ancillary studies such as immunohistochemistry and molecular studies are gaining more attention to be utilized on FNA cases. PLAG1 immunostaining, CD117, DOG1, mammaglobin, and androgen receptor (AR) are examples of commonly used immunostains in diagnosis of salivary gland lesions. MYB gene fusion, rearrangements of the MAML2 gene, and ERBB2/HER2 are examples of molecular alterations useful in diagnosis of salivary gland neoplasms. In conclusion, the aim of salivary gland cytology is to differentiate benign entities from the malignant ones and to prevent unnecessary aggressive treatments.

KEY MESSAGES

The diagnostic pitfalls are enormous in salivary gland cytology. Familiarity with cytomorphology of different entities and their cytomorphologic overlaps, and application of ancillary studies improves the diagnostic yield, patient management and prevents unnecessary aggressive procedures.

Salivary Duct Carcinoma Arising in the Submandibular Gland in a Patient with Neurofibromatosis Type 1

A 71-year-old man with neurofibromatosis type 1 (NF1) presented to our department with a 1-week history of a painful mass in the left submandibular area. Computed tomography (CT) and magnetic resonance imaging revealed an irregular-shaped tumor with a diameter of 2.0 cm in the left submandibular gland and a metastatic lymph node with a diameter of 1.0 cm adjacent to the tumor. Fluorodeoxyglucose-positron emission tomography/CT revealed increased uptake in the tumor. Fine-needle aspiration cytology revealed atypical cells, suggesting salivary duct carcinoma (SDC). Left neck dissection with resection of the tumor and submandibular gland was performed under general anesthesia. Histologic examination revealed ductal formation with a solid, cystic, cribriform, and papillary structure with intraductal comedonecrosis, diagnosing as SDC originating in the submandibular gland (pT3N1M0 pStage III). Mutational analysis of 160 cancer-related genes by next-generation sequencing (NGS) revealed a germline and frameshift mutation in the NF1 gene (p.R2408Kfs*14) and a somatic and frameshift mutation in the TP53 gene (p.C176Wfs*22). The patient received postoperative radiotherapy to the left neck area at 66 Gy. No evidence of recurrence or metastasis has been observed as of 10 months postoperatively. This is the first reported case of SDC in the submandibular gland in a patient with NF1. The mutational data by NGS may contribute to a better understanding of the oncogenesis of SDC in patients with NF1.

Algorithm for the reconstruction of the parotid region: a single institution experience

OBJECTIVE

This study aims to discuss the characteristics and treatment methods of malignant tumors in the parotid region, as well as the therapeutic effects of immediate free flap reconstruction of soft tissue for postoperative defects.

MATERIALS AND METHODS

A retrospective review was conducted on 11 cases of soft tissue flap reconstruction for postoperative defects following the resection of malignant tumors in the parotid region. Statistical analysis was performed based on clinical data.

RESULTS

Among the 11 cases of malignant tumors in the parotid region, there were 2 cases of secretory carcinoma (SC) of the salivary gland, 2 cases of squamous cell carcinoma (SCC), 2 cases of carcinosarcoma, 1 case of mucoepidermoid carcinoma (MEC), 1 case of epithelial-myoepithelial carcinoma (EMC), 1 case of salivary duct carcinoma (SDC), 1 case of basal cell carcinoma (BCC), and 1 case of osteosarcoma. Among these cases, 4 were initial diagnoses and 7 were recurrent tumors. The defect repairs involved: 8 cases with anterolateral thigh free flap (ALTF), 2 cases with pectoralis major muscle flaps, and 1 case with forearm flap. The size of the flaps ranged from approximately 1 cm × 3 cm to 7 cm × 15 cm. The recipient vessels included: 4 cases with the facial artery, 4 cases with the superior thyroid artery, and 1 case with the external carotid artery. The ratio of recipient vein anastomosis was: 57% for branches of the internal jugular vein, 29% for the facial vein, and 14% for the external jugular vein. Among the 8 cases that underwent neck lymph node dissection, one case showed lymph node metastasis on pathological examination. In the initial diagnosis cases, 2 cases received postoperative radiotherapy, and 1 case received 125I seed implantation therapeutic treatment after experiencing two recurrences. Postoperative follow-up revealed that 2 cases underwent reoperation due to local tumor recurrence, and there were 2 cases lost to follow-up. The survival outcomes after treatment included: one case of distant metastasis and one case of death from non-cancerous diseases.

CONCLUSION

Immediate soft tissue flap reconstruction is an important and valuable option to address postoperative defects in patients afflicted with malignant tumors in the parotid region.