Low Grade Carcinoma Ex-Pleomorphic Adenoma: Diagnosis and Diagnostic Challenges Caused by Fine Needle Aspiration: Report of Three Cases and Review of Literature

Abstract

Low grade carcinoma ex pleomorphic adenoma (LG CXPA) is a rare low grade malignant neoplasm arising from preexisting pleomorphic adenoma (PA). LG CXPA demonstrates no overt cytological atypia, and can be difficult to distinguish from cellular PA. Invasive growth is one of the hallmarks of LG CXPA, e.g., tumor extends beyond the capsule and into adjacent non-neoplastic tissue. However, it is known that capsular and vascular invasion, as well as the presence of stroma-rich PA in soft tissue without a capsule (pseudopodia) can be seen in PA. These histological findings have no prognostic significance and are not diagnostic of malignancy. In addition, recurrent PA typically presents as numerous nodules extending into soft tissue and skeletal muscle, which again are not considered malignant features. Thus, "infiltrative growth" of LG CXPA is difficult to define and diagnosis is challenging to many practicing pathologists. In this study, we report three cases of LG CXPA. We review the diagnostic criteria for LG CXPA, and discuss the diagnostic challenges caused by fine needle aspiration (FNA) changes. FNA is widely used as a cost-effective, quick and accurate method for diagnosing salivary gland lesions. Histological changes post-FNA are usually focal and mild, and are not causes of diagnostic difficulties. According to our knowledge, this is the first report of LG CXPA complicated with FNA changes.

The accurate cytological diagnosis of salivary carcinoma ex pleomorphic adenoma may be hampered by myoepithelial differentiation

“…Until 1999, the FNA findings in only 41 cases of carcinoma ex pleomorphic adenoma had been reported 3 . Since then, 33 additional cases with modern classification criteria have been retrieved from the literature 2‐4,9,16,17 . Of these, 19 showed non‐MED and 14 (including our case) showed MED (Table 1).…”

“…Klijanienko et al, 3,12 reported 26 cases: 19 showing non‐MED and seven with MED (three epithelial‐myoepithelial carcinomas, one basal cell adenocarcinoma, one polymorphous low‐grade carcinoma, and two adenoid cystic carcinomas). Covinsky et al 17 described three cases of low‐grade pleomorphic adenocarcinoma arising in pleomorphic adenoma, all with MED. All three cases were false‐negative on cytological FNA.…”

Myoepithelial Carcinoma Ex Pleomorphic Adenoma of the Submandibular Gland: A Case Report

“…When malignancy is suspected, the diagnostic modality of choice is the FNA. Although it is a fast, safe, and cost-effective choice, it has limitations that are mainly attributed to sampling errors [ 13 ]. Core-needle biopsy under ultrasound guidance has been described as an accurate and safe method of diagnosing salivary gland tumors, with some studies providing significant superiority compared to FNA [ 14 ].…”

A case of carcinoma ex pleomorphic adenoma arising from multinodular pleomorphic adenoma of the buccal region

“…Compared to excisional biopsy, FNAB is quick, simple, and minimally invasive. Moreover, FNA studies significantly reduce complications, including facial nerve damage, tumor implantation, fistula formation, and tissue reactions, which make subsequent surgery difficult . Meanwhile, a serious matter remains in FNA studies.…”

“…Moreover, FNA studies significantly reduce complications, including facial nerve damage, tumor implantation, fistula formation, and tissue reactions, which make subsequent surgery difficult. 13 Meanwhile, a serious matter remains in FNA studies. Several studies have demonstrated that the sensitivity of FNAC when diagnosing Ca-ex-PA is 29%-50% and that the reliability has never been shown to be high.…”