The key radiologic and cytomorphologic features of oncocytic and oncocytoid lesions of the salivary gland

Abstract

Oncocytic and oncocytoid lesions represent a distinct subset of salivary gland lesions. True oncocytic lesions of the salivary gland are entirely composed of oncocytes. These are characterized by the presence of abundant eosinophilic granules due to the presence of abundant cytoplasmic mitochondria. Oncocytic lesions of the salivary gland include oncocytosis, oncocytoma, and oncocytic carcinoma. In addition to the true oncocytic lesion, there exists another group of salivary gland lesions, which demonstrate cells with abundant and occasionally granular cytoplasm. These are often termed as “oncocytoid” lesions. The recently proposed Milan System for reporting salivary gland cytology clearly states that fine‐needle aspiration specimens representing oncocytic/oncocytoid lesions of salivary gland cannot effectively distinguish between a nonneoplastic lesion, benign and malignant neoplasms. Therefore, most lesions lacking classic cytomorphologic features will be classified under the umbrella diagnostic term of “Salivary Gland Neoplasm of Uncertain Malignant Potential” (SUMP). In this review, we discuss and illustrate key clinicopathologic and radiologic features that can help the practicing cytopathologist narrow down the differential and provide the best management based diagnosis.

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.…”

“…First, "clear cell" is generally used to describe the artifactual clearance of a cell's cytoplasm resulting from formalin fixation in histology and the corresponding cellular morphology in cytologic preparation is mostly oncocytoid cells with granular, foamy, or vacuolated cytoplasm, overlapping with the oncocytic/oncocytoid subcategory. 4,10,11 Second, no SUMP cases were classified as cellular neoplasm with clear cell features in the previous series. [4][5][6][7][8][9][10] In addition, we created a new "not otherwise specified (NOS)" subcategory to accommodate SUMP cases that are neither basaloid nor oncocytic/oncocytoid.…”

“…We dropped cellular neoplasm with clear cell features subcategory and merged it with the oncocytic/oncocytoid subcategory for 2 reasons. First, “clear cell” is generally used to describe the artifactual clearance of a cell’s cytoplasm resulting from formalin fixation in histology and the corresponding cellular morphology in cytologic preparation is mostly oncocytoid cells with granular, foamy, or vacuolated cytoplasm, overlapping with the oncocytic/oncocytoid subcategory 4,10,11 . Second, no SUMP cases were classified as cellular neoplasm with clear cell features in the previous series 4‐10 .…”

Cytomorphological findings in diagnosis of Warthin tumor

“…Degenerative oncocytes are common in the epithelial layer and spill into the fluid of the lumen. This condition commonly occurs in WT and indicates the apoptosis of oncocytes in the luminal fluid [7,11], and these degenerated oncocytes may resemble squamous cells [16]. The percentages of degenerated oncocytic cells were 65% and 66% in the studies of Flezar et al and Viguer et al [4,11].…”

“…Oncocytes are typical cell components of WT but excessive presence of oncocytic cells in the field may lead to a diagnostic mistake such as oncocytoma [15][16][17]. Werma et al reported that oncocytic epithelial cells are more often seen as papillary fragments, sheets, acini, and isolated appearances in cases of oncocytoma.…”