Polymorphous adenocarcinoma of the salivary glands: reappraisal and update

Abstract

Although relatively rare, polymorphous adenocarcinoma (PAC) is likely the second most common malignancy of the minor salivary glands (MiSG). The diagnosis is mainly based on an incisional biopsy. The optimal treatment comprises wide surgical excision, often with adjuvant radiotherapy. In general, PAC has a good prognosis. Previously, PAC was referred to as polymorphous low-grade adenocarcinoma (PLGA), but the new WHO classification of salivary gland tumours has also included under the PAC subheading, the so-called cribriform adenocarcinoma of minor salivary glands (CAMSG). This approach raised controversy, predominantly because of possible differences in clinical behaviour. For example, PLGA (PAC, classical variant) only rarely metastasizes, whereas CAMSG often shows metastases to the neck lymph nodes. Given the controversy, this review reappraises the definition, epidemiology, clinical presentation, diagnostic work-up, genetics, treatment modalities, and prognosis of PAC of the salivary glands with a particular focus on contrasting differences with CAMSG.

Fine needle aspiration cytology of cribriform adenocarcinoma of minor salivary gland, a recently defined entity

“…The critical differential diagnosis on aspirates from metastatic sites is PTC . Presence of metachromatic matrix and flocculent mucoid material, with lack of colloid has been found to be useful in distinguishing CAMSG from PTC on FNA . We identified glomeruloid structures with a narrow stalk, recapitulating the histological features of CAMSG, which are only rarely described in PTC.…”

“…Gailey et al reported the cytology of CAMSG in benchtop aspirates of a biopsy‐confirmed tongue CAMSG with nodal metastasis. They identified tumour cells in sheets, papillary fronds and tips, and occasional cribriform structures, accompanied by nuclear features of PTC and moderate amount of fluffy cytoplasm . Appukutty et al observed basaloid tumour cells in sheets, papillae and trabecular pattern in an upper cervical lymph node FNA.…”

“…Initially described as cribriform adenocarcinoma of tongue , it has since been reported at other minor salivary gland locations, leading to a modification in nomenclature to CAMSG . Previously, these cases were diagnosed as polymorphous low‐grade adenocarcinoma, currently known as polymorphous adenocarcinoma (PAC) . However, its characteristic histological features, genetics and, most importantly, clinical behaviour with greater propensity for lymph node metastases warrant its separation from the latter.…”

“…1,2 Previously, these cases were diagnosed as polymorphous low-grade adenocarcinoma, currently known as polymorphous adenocarcinoma (PAC). [3][4][5] However, its characteristic histological features, genetics and, most importantly, clinical behaviour with greater propensity for lymph node metastases warrant its separation from the latter. The latest World Health Organisation classification includes CAMSG under PAC, but considers it an emerging entity, awaiting further evidence to justify it being separated.…”

Analysis of the Clinical Relevance of Histological Classification of Benign Epithelial Salivary Gland Tumours

“…Papillary configuration is frequently seen in many salivary neoplasms, e.g., WT, oncocytoma, polymorphous low-grade adenocarcinoma (nowadays, polymorphous adenocarcinoma, PAC; [49]), papillary cystadenoma, etc. Ductal papillomas comprise a special group of adenomas with unique papillary features.…”