Cytopathology of acinic cell carcinoma: A study of 50 cases, including 9 with high‐grade transformation

Abstract

BACKGROUND:Although largely readily recognizable in tissue sections, acinic cell carcinoma (ACC) remains diagnostically problematic in fine-needle aspiration (FNA) cytopathology. The authors undertook an analysis of a large series of ACC aspirates, including acinic cell carcinoma with high-grade transformation (ACC-HGT). METHODS: The authors searched their cytopathology files for ACC cases with histopathologic confirmation. FNA biopsy was performed according to standard techniques. RESULTS: Fifty FNA biopsy cases of ACC (including 36 of parotid origin [72%]) from 41 patients (female to male ratio, 1.4:1; age range, 23-84 years; average, 54 years) met the study inclusion requirements. Primary neoplasm aspirates were most common (72%), and they were followed by recurrent tumors (16%) and metastases (12%). A precise cytologic diagnosis was made for 64%. Three of 9 ACC-HGT cases (33%) were correctly interpreted as such; 98% of conventional ACC cases were correctly graded as low-grade. With the Milan classification system, 74% fit into the malignant category.Ancillary testing was performed for only 36%. Conventional ACC had moderately to highly cellular smears; monotonous cells in aggregates and single forms; rounded nuclei; and microvacuolated, finely granular, oncocyte-like, or nonspecific cytoplasm. ACC-HGT smears contained larger nuclei, high nuclear to cytoplasmic ratios, coarse nuclear chromatin, and a loss of cytoplasmic granules/vacuoles. CONCLUSIONS: A correct diagnosis of ACC via FNA biopsy was made in almost two-thirds of the cases. With the Milan classification, 84% of the cases would have been classified as malignant or suspicious for malignancy. An absence of conventional serous acinar cell morphology in some cases as well as an absence of ancillary immunohistochemistry testing in almost two-thirds of the cases prevented even better diagnostic performance. Cancer

Multi‐institutional validation of a modified scheme for subcategorizing salivary gland neoplasm of uncertain malignant potential (SUMP)

“…On surgical follow‐up of oncocytic/oncocytoid SUMP, the most common benign neoplasm was Warthin tumor (22.8%), followed by oncocytoma (10.9%), and the most common malignant diagnosis was mucoepidermoid carcinoma (22.8%), followed by acinic cell carcinoma (14.9%). In typical cases, the FNA diagnosis of the previously mentioned tumors is usually straightforward 11,24‐27 . Occasional cases lacking classic cytomorphologic features, particularly those with superimposed reactive or metaplastic changes, would be placed in SUMP under this subcategory.…”

“…In typical cases, the FNA diagnosis of the previously mentioned tumors is usually straightforward. 11,[24][25][26][27] Occasional cases lacking classic cytomorphologic features, particularly those with superimposed reactive or metaplastic changes, would be placed in SUMP under this subcategory. Lubin et al demonstrated a high ROM in oncocytoid neoplasms with mucinous background (83.0%) and a low ROM in cases with cystic background (6.3%).…”

Utility of NR4A3 on FNA cytology smears and liquid‐based preparations of salivary gland

“…5,6 Some studies have shown that the diagnosis of AciCC was correctly made in only two-thirds of the cases, largely due to the absence of conventional serous acinar morphology and/or lack of ancillary studies. 18 Indeed, FNAC of AciCC is not infrequently categorized as oncocytic/oncocytoid SUMP (category IVB) in the Milan System. 7,8 Existing ancillary studies using IHC for SOX10 and DOG1 as markers of acinar and intercalated duct differentiation may assist in the cytologic diagnosis of AciCC.…”

“…Moreover,10%–29% of AciCCs are associated with TALP, which may lead to misdiagnoses of the tumors as reactive lymph nodes 5,6 . Some studies have shown that the diagnosis of AciCC was correctly made in only two‐thirds of the cases, largely due to the absence of conventional serous acinar morphology and/or lack of ancillary studies 18 . Indeed, FNAC of AciCC is not infrequently categorized as oncocytic/oncocytoid SUMP (category IVB) in the Milan System 7,8 …”

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

“…These cells are arranged in different cytoarchitectural patterns. 51 AciCC is one of the most challenging malignancies to diagnose on cytology, with a high rate of false negative diagnoses (ranging from 13.7% to 68%). [52][53][54][55] The reason is that AciCCs may be associated with a lymphoid infiltrate, such as secondary lymphoid follicle formation.…”