Australian Society of CytologyCase of the Month
April 2003 - Answer and Discussion
Salivary gland neoplasm - cannot exclude Adenoid Cystic Carcinoma of the Parotid Gland
Discussion
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The salivary gland was removed, and contained an Adenoid Cystic Carcinoma.
The characteristic findings on fine needle aspiration of Adenoid Cystic Carcinomas of the salivary glands are well described. On Giemsa stained smears, magenta hyaline spherical globules are a classic finding. Of note is that the same globules are pale, semitranslucent and can be easily overlooked on a Pap stained smear. Also of note is that there is variation in the size of the fragments, most being medium to large in size. The stromal fragments may be isolated, in groups or associated with cells. While much of the stroma may be hyaline and homogenous in quality, variation in stromal texture is also a feature, with granular, fibrillary and radially arranged stroma being visible. The cells from an adenoid cystic carcinoma are small, with round to oval hyperchromatic nuclei and scant cytoplasm. Tight aggregates of cells with smooth margins are formed, which may contain rounded spaces. Single cells with or without stroma may be present as are bare nuclei.
The differential diagnosis includes pleomorphic adenoma. A clue to the diagnosis of pleomorphic adenoma is the presence of isolated cells with a plasmacytoid appearance. Also present may be groups of cells arranged in large loose clusters with fuzzy edges and a spindle cell core- described as a "sunburst pattern". Fibrillary chondromyxoid stroma is a well described feature, as is myxoid stroma with associated spindle cells. Hyaline globules are not specific to the diagnosis of adenoid cystic carcinoma, also being seen in pleomorphic adenoma, polymorphous low grade adenocarcinoma, and epithelial-myoepithelial carcinoma. Basal cell adenoma is another differential diagnosis, and differentiation between the two entities may not be possible.
All adenoid cystic carcinomas are biologically aggressive, and we must look hard for clues to this possible diagnosis in aspirates from salivary gland neoplasms, even if the lesion appears well circumscribed on imaging . Definite diagnosis may not be possible, but the possiblity should be raised if atypical stromal or epithelial arrangements are present.
Further Reading:
- Lee S, Cho K, Jang J, Ham E. Differential Diagnosis of Adenoid Cystic Carcinoma from Pleomorphic Adenoma of the Salivary Gland on Fine Needle Aspiration Cytology. Acta Cytologica. 1996;40:1246-1252
- Stanley M, Horwitz C, Henry M, Burton L, Lowhagen T. Basal-Cell Adenoma of the Salivary Gland: A Benign Adenoma that cytologically mimics adenoid cystic carcinoma. Diagnostic Cytopathology 1988; 4:342-346
- Nagel H, Hermann J, Laskawi R, Chilla R. Droese M. Cytologic Diagnosis of Adenoid Cystic Carcinoma of Salivary Glands. Diagnostic Cytopathology 1999; 20:358-366.
- Kawahara A, Harada H, Kage M, Yokoyama T, Kojiro M. Characherization of the epithelial components in Pleomorphic Adenoma of the Salivary Gland. Acta Cytol 2002; 46:1095-1100
