A rare tumor of salivary gland: Diagnostic Dilemma on fine needle aspiration cytology

Oncocytic features in salivary duct carcinoma, a potential pitfall for misdiagnosis as Warthin tumor in fine needle aspiration specimens: A cytomorphologic analysis of 14 cases

BACKGROUND

Salivary duct carcinoma (SDC) is an uncommon and highly aggressive primary salivary gland neoplasm. Cytomorphologic features of SDC include cellular smears, nuclear atypia, prominent nucleoli, cribriform and papillary architecture, and background necrosis. The presence of oncocytic features has been described but not adequately characterized in the current literature.

METHOD

This study cohort consisted of 14 cases of histologically proven SDC with previous salivary gland fine needle aspiration (FNA). The cytologic material of each case was semi-quantitatively analyzed and evaluated for various cytomorphologic, architectural, and background features.

RESULTS

Twelve SDCs were located in the parotid gland and two in the submandibular gland. In two cases the initial cytologic diagnoses was Warthin tumor or favor Warthin tumor. Moderate to marked degree of oncocytic changes were noted in all cases except one case. Nuclear atypia was variable with most cases exhibiting moderate to high-grade nuclear features, while four cases demonstrated low-grade nuclear cytomorphology. Cytoplasmic vacuolation was seen in nine cases and variable amount of background necrosis was observed in eight cases. Cribriform and papillary architecture was recognized in only six cases. Background lymphocytes were absent in all but one case.

CONCLUSIONS

Precise diagnosis of SDC based on cytomorphologic features alone can be challenging. Oncocytic change is one of the most consistent features observed in this case series and when associated with less pronounced cytologic atypia, can potentially lead to misdiagnosis as Warthin tumor. SDC should be considered in the differential diagnosis of oncocytic salivary gland neoplasms where precise diagnosis is not possible.

Salivary duct carcinoma

PURPOSE OF REVIEW

The review puts new information on geno- and phenotype of salivary duct carcinoma (SDC) in the perspective of the updated 2017 WHO classification.

RECENT FINDINGS

The proportion of SDC is increasing. This may be because of a true rise in incidence, but certainly to better diagnostic tests and changed WHO definitions. In this light, a substantial proportion of carcinoma expleomorphic adenoma is now attributed to the category of SDC. 'Low-grade SDC' and 'SDC in-situ' of the former WHO classification, are now named low-grade and high-grade intraductal carcinoma (IDC), respectively. Recent series quantify biologic aggressiveness: perineural growth, vascular invasion, and extracapsular extension in lymph node metastasis are each observed in two out of three patients with SDC. Most patients die within 3 years, but once 5-year disease-free survival is reached, further disease activity is exceptional. The typical molecular biological profile with high human epidermal growth factor receptor 2 and androgen receptor expression is increasingly successfully exploited in clinical trials for advanced SDC.

SUMMARY

The aggressive SDC is increasingly diagnosed. Despite intensive combined surgery and radiation therapy, many patients recur, for whom new bullets, targeting the molecular biological mechanisms, are the subject of ongoing clinical trials.

HER2/HER3-positive metastatic salivary duct carcinoma in the pleural effusion: A case report

Salivary duct carcinoma (SDC) is an aggressive form of salivary gland tumor, and SDC patients tend to be older men, more commonly in advanced stage with a poorer prognosis. Although the cytological characteristics of SDC on fine-needle aspiration cytology have been well-described at the primary site, they have not been explored in metastasis. Here we reported a case of HER2/HER3-positive metastatic SDC in the lung and pleural effusion. The patient was a man in his 50s who had undergone extended total parotidectomy in 2008. He was originally diagnosed as having HER2-positive left parotid SDC. Six years later a mass was discovered in the left lung by chest computed tomography (CT) and was diagnosed as metastatic SDC by both bronchial biopsy and cytology. Subsequently he had a recurrent SDC in the left pleural effusion and died of respiratory failure. Cytological findings from bronchial brushing smear showed small sheet clusters in a slightly necrotic background. In the pleural effusion cytology, tumor cells appeared as ball-like clusters of epithelioid cells with apocrine-like findings. In immunocytochemistry, HER3 of SDC cells in pleural effusion was significantly overexpressed relative to the matched primary tumor, even though HER2 amplification did not change. Cytological findings and HER family receptors differed between the primary and metastatic SDC. Therefore, molecular tests, such as protein expression and gene amplification using cytological specimens, may become important in future when determining therapy strategies in patients with distant metastasis.