High‐grade transformation/dedifferentiation of an adenoid cystic carcinoma of the minor salivary gland to myoepithelial carcinoma

Abstract

High-grade transformation (HGT)/dedifferentiation is an unusual phenomenon in salivary gland carcinomas. Here we report a case of adenoid cystic carcinoma (ACC) with HGT/dedifferentiation to myoepithelial carcinoma, occurring in the epipharynx of a 42-year-old woman. The surgically resected tumor was a pedunculated mass, 31 × 25 mm in size, which had two histologically distinct carcinomatous areas, including a high-grade sarcomatoid area composed of pleomorphic spindle cells and an area consisting of low-grade typical ACC. These two components gradually changed from the low-grade to the high-grade component. MIB-1 index in the low-grade and high-grade component was 15% and 50%, respectively. An immunohistochemical profile of the high-grade component showed immunoreactivity for α-SMA, p63, calponin and focal S100, as well as for several cytokeratin markers, which were compatible with the features of myoepithelial carcinoma. In contrast, the immunohistochemical profile of the low-grade component coincided with that of typical ACC. This HGT/dedifferentiation to myoepithelial carcinoma is extremely rare. The pathogenesis of HGT/dedifferentiation in salivary gland carcinomas still remains largely unknown, regardless of the presence or absence of myoepithelial differentiation. Further studies are required due to the more aggressive biological behavior and poorer prognosis associated with ACC with HGT/dedifferentiation, compared with conventional ACC.

Adenoid Cystic Carcinoma with Transformation to High Grade Carcinomatous and Sarcomatoid Components: A Rare Case Report with Review of Literature

“…Since the first documentation of "dedifferentiated" AdCC by Cheuk et al [3], a total of 48 AdCC cases with dedifferentiation/HGT have been described in the literature till date (Table 1). Only three cases of low grade AdCC transforming to sarcomatoid component have been reported in the literature (Table 2) [3,5,6]. Herein, we report the first case of AdCC arising in submandibular gland showing synchronous transformation to high grade carcinomatous and also to a sarcomatoid component.…”

“…Table 3 and Figs. 4,5,6,7 show the comparative immunohistochemical features of all three components.…”

Dedifferentiated secretory breast carcinoma with fibrosarcomatous features harboring an ETV6‐NTRK3 fusion in both components

“…Dedifferentiation, also known as high‐grade transformation, is a well‐documented means of tumor progression occurring in translocation‐driven salivary gland type carcinomas, 1 being reported in virtually every subtype, including adenoid cystic carcinoma, 2,3 mucoepidermoid carcinoma, 4,5 clear cell carcinoma not otherwise specified (formerly hyalinizing clear cell carcinoma) 6,7 and secretory carcinoma 8 . Dedifferentiation in these tumors most frequently takes the form of a high‐grade carcinoma 1,3,6‐14 .…”

“…Dedifferentiation in these tumors most frequently takes the form of a high‐grade carcinoma 1,3,6‐14 . Conversely, sarcomatous dedifferentiation is rare 2,4,5 . Among the molecularly confirmed cases of secretory carcinoma with dedifferentiation, 8‐14 none have shown sarcomatous dedifferentiation.…”

A series Cases study of Carcinomas derived from myoepithelial cells in head and neck regions

“…Carcinomas derived from myoepithelial cells in head and neck regions (CMCHN) can be mainly divided into three types: 1) myoepithelial carcinoma (MEC), which is purely composed of myoepithelial cells and accounted for < 2% of all salivary gland carcinomas [6]; 2) the epithelial myoepithelial carcinoma (EMC, also called adenomyoepithelioma), represents approximately 1% of salivary gland tumors [7], and is histologically consist of a biphasic arrangement of inner luminal ductal cells and outer myoepithelial cells; 3) adenoid cystic carcinoma (AdCC), a biphasic tumor comprised of ductal and myoepithelial cells which tends to be arranged in a more cribriform pattern. [8] The main therapy for CMCHN is surgical resection with clear margins, with or without pre-/post-operative radiation [9]. However, due to the rarity of this carcinoma, its clinical characteristics, proper treatment modalities, and their correlation with prognosis remain unclear [9][10][11].…”