Rare Salivary Gland Tumors: When Cytology Uncovers the Unexpected
"Exploring the Unusual: How Cytological Analysis Aids in Diagnosing Acinic Cell Carcinoma"
Acinic Cell Carcinoma (AcCC) is a slow-growing malignant tumor primarily found in the parotid gland, a major salivary gland. It is rare to find it in the submandibular gland, minor salivary glands, or in heterotopic salivary gland tissue (HSGT) – salivary gland tissue in an abnormal location. The challenge? These unusual locations and presentations can easily lead to delayed or incorrect diagnoses.
Fine Needle Aspiration Cytology (FNAC) is a vital tool for diagnosing AcCC before surgery. However, diagnosing AcCC through cytology can be tricky, and misdiagnosis can impact long-term prognosis. This article explores two unusual cases of AcCC, highlighting the importance of cytological features in preoperative diagnosis.
We will delve into a case of AcCC developing in HSGT and another presenting as a synchronous bilateral tumor, emphasizing how clinical suspicion combined with cytological analysis are key to accurate diagnosis. Discover how a skilled cytopathologist plays a crucial role in preliminary diagnosis, ensuring timely and appropriate treatment.
How Common Is Acinic Cell Carcinoma?
Acinic cell carcinoma (AciCC) accounts for about 6–7% of salivary gland neoplasms and is the second most common salivary gland malignancy in children, according to a 2023 review. A population-based study analyzed 2,226 AciCC cases, examining demographic trends, clinical characteristics, treatment strategies, and outcomes. The CDC says cancer data are used to understand rates and trends, support research, measure progress in prevention and control, address disparities, and improve outcomes.
Cytologic Recognition and Diagnostic Challenges
Pathology Outlines characterizes salivary-gland acinic cell carcinoma as a malignant epithelial neoplasm showing serous acinar differentiation, including cytoplasmic zymogen granules in at least some tumor cells. A cited cytology review describes dedifferentiated AciCC as an uncommon variant in which usual low-grade AciCC coexists with a dedifferentiated component. The supplied sources also report that selected patients with early-stage parotid AciCC and no adverse pathological features had low recurrence in a series, with one recurrence among 18 patients after a median 64 months of follow-up.
From Nasse’s Description to Cancer Research Milestones
A Springer Nature chapter reports that Nasse first described acinic cell carcinoma in 1892. The tumor was initially considered benign, although its malignant behavior was later recognized. More broadly, the NCI’s cancer-research timeline identifies 1775 as a milestone: Percivall Pott linked chimney-soot exposure with squamous cell carcinoma of the scrotum among chimney sweeps.
Unveiling Acinic Cell Carcinoma: Diagnostic Clues and Cytological Insights
ACCC is an uncommon salivary gland tumor, generally encapsulated and less than 3 cm in size. It is more common among males in their third decade of life and has a rare familial prevalence. Alterations in chromosomes, such as 6q rearrangement, loss of the Y chromosome, and gain of chromosomes 7 and 8, are related to the occurrence of familial AcCC. Another factor is radiation exposure.
- Microacinar Groupings: Presence of cells in microacinar groupings within the smear.
- Cellular Features: Cells display abundant, finely vacuolated cytoplasm.
- Nuclear Characteristics: Minimal anisokaryosis and bland nuclear chromatin observed.
- Background Elements: Presence of many stripped nuclei.
Cytology Can Miss AciCC
A report on cytological assessment of head and neck swellings describes two cases of acinic cell carcinoma incorrectly identified as Warthin’s tumor on cytology, resulting in false-negative findings. The report attributes these examples to cases published by Das et al. (2016), Salehi and Maleki (2018), and Köybaşıoğlu et al. (2020). These cases illustrate that cytologic assessment may not always identify AciCC correctly.
Diagnostic Value and Variable Outcomes
A report of two unusual AciCC cases highlights the cytopathologist’s role in preliminary diagnosis. At the same time, the supplied review describes AciCC as generally associated with a good prognosis while noting that some patients develop local or distant recurrence. A separate 2022 report says conventional AciCC had good long-term outcomes in a large two-center study with comparable treatment strategies, and that nodal disease and perineural invasion were uncommon.
Distinguishing AciCC from Secretory Carcinoma
A 2021 review frames salivary secretory carcinoma (SC) and acinic cell carcinoma (AciCC) as two rare tumors arising in the salivary glands of the head and neck. It focuses on their differential diagnosis and treatment, noting that the distinction became relevant after the World Health Organization classified SC as a separate entity. Another supplied source notes that AciCC’s histologic types and cell morphology are complex and diverse and can resemble pleomorphic adenoma.
The Critical Role of Early Detection
ACCC, while rare and slow-growing, demands careful attention due to its potential for misdiagnosis. It can develop in unusual locations such as the submandibular or minor salivary glands or, extremely rarely, in HSGT.
Emerging Evidence and Prognostic Questions
A 2026 American Society of Clinical Oncology abstract is titled “Real-world treatment patterns and survival outcomes in acinic cell carcinoma of the breast: A National Cancer Database study.” Its title indicates a focus on treatment patterns and survival outcomes, but the supplied snippet does not provide results. A 2023 review notes that although AciCC is traditionally considered low grade, a subset shows high-grade features and higher mortality, underscoring the importance of understanding which cases behave more aggressively.
Rarity and Treatment Context
Salivary Gland Cancer UK describes acinic cell carcinoma as a rare malignant salivary-gland neoplasm, constituting 1–6% of all salivary gland tumors, primarily found in the parotid gland and typically presenting as a lump. The supplied review of targeted and systemic therapy discusses more aggressive non-ACC histologies, including salivary duct carcinoma and adenocarcinoma, for which early systemic therapy may be indicated. It says molecular and immunohistochemical testing for HER2 overexpression, androgen receptor positivity, and NTRK fusions can guide treatment selection in those cases.
FNAC plays a vital role in diagnosing ACCC, and cytopathologists are critical to its preliminary diagnosis. It's easily missed clinically, radiologically, and cytologically.
Through increased awareness and vigilance, healthcare professionals can improve early detection rates, ultimately leading to more effective treatment and better outcomes for individuals affected by this rare salivary gland tumor.