High Grade Transformation in Adenoid Cystic Carcinoma of the Parotid: Report of a Case with Cytologic, Histologic and Immunohistochemical Study

Abstract

Adenoid cystic carcinoma (ACC) constitutes about 4% of salivary epithelial tumors and is the second common malignant epithelial salivary gland tumor involving both the major and minor salivary glands. High grade transformation in ACC is a recently recognized entity with only a few cases reported in literature. We report the first case of ACC with high grade transformation involving the parotid. A 54-year-old man with a history of right parotid painful swelling from 1.5 years presented with recent increase in size of the swelling and facial paresis of 2 months duration. The locally invasive salivary neoplasm was composed predominantly of an undifferentiated carcinoma with foci of conventional ACC occupying less than 10% of tumor area. Immunohistochemical study of the undifferentiated component as compared to conventional ACC showed greater over-expression of p53 and Ki-67. Her-2/Neu was negative in both components. Recognition of occasional clusters of basaloid cells and hyaline globules in association with larger poorly differentiated malignant cell population in aspiration smears can help in cytological diagnosis. The acquisition of high proliferation index and over-expression of p53 may be the probable factors involved in the pathogenesis of high grade transformation in a conventional ACC.

Metastatic adenoid cystic carcinoma with high‐grade transformation (“dedifferentiation”) in pleural effusion and neck lymph node: A diagnostic challenge on cytology?

“…Gathering complete and accurate clinical history and radiological data, obtaining adequate diagnostic material for ancillary studies (Cell block), and comparing the morphology of the tumor with that of the patient's known primary are essential for the diagnosis of metastatic ACC, with or without HGT, in effusion or in other unusual locations. Since ACC‐HGT has far more propensity than conventional ACC to metastasize to lymph node (43%‐57% vs 5%‐25%) and distant metastatic sites including effusion, 11,12 the non‐specific features of a high‐grade carcinoma would be more likely at metastatic sites than in the primary tumor, and the classification may be limited to “high‐grade carcinoma.” In contrast, an adequately sampled tumor from the primary site may show features of both the conventional and the higher grade component facilitating the diagnosis 14 . Especially, recognition of occasional clusters of basaloid cells and/or hyaline globules, when present, in association with larger poorly differentiated malignant cell population in aspiration smears can be a helpful clue in cytological diagnosis 14 …”

Genetic profile of adenoid cystic carcinomas (ACC) with high-grade transformation versus solid type

“…To date, genetic studies on ACC-HGT have almost exclusively been restricted to protein expression studies with immunohistochemistry [1,3,4,12,15,17,25,26]. Here, we applied a high-resolution microarray CGH analysis in an attempt to uncover genes involved in high-grade transformation of ACC, supplemented by immunohistochemical analysis of Ki-67 and p53 and clinico-pathological data.…”

“…This phenomenon has been referred to as dedifferentiation or high-grade transformation (ACC-HGT) and there have been only 33 reported cases so far [1,3,4,10,12,[15][16][17]25,26]. This process was first believed to occur in low-grade ACCs without morphological recognizable changes, as an abrupt transition, but recently cases have been described showing a gradual transformation of solid ACC into high-grade adenocarcinoma [25,26].…”

Anaplastic Myoepithelial Carcinoma of the Sinonasal Tract: an Underrecognized Salivary-Type Tumor Among the Sinonasal Small Round Blue Cell Malignancies? Report of One Case and a Review of the Literature

“…Furthermore, the high-grade (''dedifferentiated'') components in ADCC-Ds reported by by Malhotra et al, Chao et al and Moles et al also displayed an absence of myoepithelial differentiation [29][30][31].…”