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

Abstract

High‐grade transformation (HGT) or “dedifferentiation” is an uncommon phenomenon among salivary gland carcinomas including adenoid cystic carcinoma (ACC), which is important to recognize because it is associated with increased tumor aggressiveness, with a high propensity for lymph node and distant metastases. ACC with HGT is histologically characterized by a distinct population of poorly differentiated cells with loss of the typical biphasic ductal and myoepithelial differentiation seen in conventional ACC, associated with pleomorphism, necrosis and increased mitotic activity. We report the cytologic features of a case of metastatic ACC‐HGT in cervical lymph node and effusion, which, to the best of our knowledge, have not been described previously. When ACC presents both in atypical locations and with HGT, the danger of misdiagnosis is increased if the clinical history is lacking, incomplete or inaccurate. Since ACC‐HGT are rare (and possibly underdiagnosed) and do not have a specific set of cytological and/or immunohistochemical features, it is important for practicing cytopathologists to be aware of the possibility of encountering them, especially in specimens from patients with a history of ACC, in order to render the correct diagnosis.

Primary cutaneous adenoid cystic carcinoma: a clinicopathologic, immunohistochemical, and fluorescence in‐situ hybridisation study of 13 cases

“…15 Approximately 56 cases of ACC with HGT have been recognised in the English literature to date. 15,18,21,[34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] The most commonly involved sites by HGT were the submandibular gland and paranasal sinus, followed by the parotid gland and palate. 'HGT' is characterised by a distinct population of anaplastic cells with loss of the biphasic ductal-myoepithelial differentiation, clearly separated from conventional ACC.…”

“…in 1999 15 . Approximately 56 cases of ACC with HGT have been recognised in the English literature to date 15,18,21,34–49 . The most commonly involved sites by HGT were the submandibular gland and paranasal sinus, followed by the parotid gland and palate.…”

Fine needle aspiration of salivary gland carcinomas with high‐grade transformation: A multi‐institutional study of 22 cases and review of the literature

“…The cytomorphologic findings of HGT from previous reports are summarized in Table 3. [10][11][12][13][14][15][16][17] Among 8 single case reports, all FNA specimens, except for 1 report of metastatic SGC with HGT in pleural effusion cytology, 17 were from primary salivary gland tumors. [10][11][12][13][14][15][16] All reported FNA specimens were diagnosed as malignant.…”

“…4,[6][7][8] Preoperative recognition of a high-grade component by fine needle aspiration (FNA) would therefore be useful for patient prognostication as well as for influencing patient management, including presurgical planning. 9 Despite wide recognition of this disease concept, only a few case reports describing the cytological features of SGC with HGT have been published, [10][11][12][13][14][15][16][17] and comprehensive FNA case series are lacking. Using a multi-institutional approach, we describe the clinical and cytomorphologic features of the largest FNA series of SGC with HGT and provide a comprehensive review of the literature.…”

Bioinformatics identification of the candidate microRNAs and construction of a competing endogenous RNA regulatory network in lacrimal gland adenoid cystic carcinoma high‑grade transformation

“…A study shows the lymph node metastasis rate of LACC-HGT is higher compared with LACC (43-57% vs. 5-25%) (11). According to a previous report, LACC-HGT accelerates the process of tumor local recurrence and distant metastasis, resulting in increased mortality, shortened postoperative survival and poor outcomes of conventional treatment (12). Non-coding RNAs (ncRNAs) are generally defined as a wide class of RNAs without protein-coding function, but these have regulatory functions in the various biological processes, such as post-transcriptional regulators, regulation of mitochondrial biology and metabolic control.…”