Predictors of Outcome in the Phenotypic Spectrum of Polymorphous Low-grade Adenocarcinoma (PLGA) and Cribriform Adenocarcinoma of Salivary Gland (CASG)

Abstract

Polymorphous low-grade adenocarcinoma (PLGA) shows histologic diversity with fascicular and targetoid features while cribriform adenocarcinoma of salivary gland (CASG) demonstrates predominant cribriform and solid patterns with glomeruloid appearance and optical clear nuclei. The current study is designed to identify pathologic features that may predict clinical outcome in 69 PLGA/CASG. Seven patients had recurrences or distant metastasis, including 3 local recurrences, 2 nodal metastases, and 2 distant metastases. The following histologic factors predicted disease-free survival on univariate analysis: tumor size, bone invasion, lymphovascular invasion, tumor necrosis, ≥10% papillary pattern, and ≥30% cribriform pattern. On multivariate analysis, 10% of papillary pattern and 30% cribriform pattern were independent prognostic factors of disease-free survival. Histologic classification of the 69 tumors (based on the prior reported definition of CASG) showed 21 CASGs (30%), 23 PLGAs (33%), and 22 (32%) with indeterminate features of PLGA and CASG. In addition, 3 (4%) tumors demonstrated a predominant papillary pattern (≥50%). Interestingly, not all CASGs were located in the minor salivary gland and 2 tumors were identified in the parotid. One patient died from her disease and she harbored a CASG with >30% cribriform pattern. In conclusion, tumor size, bone invasion, and lymphovascular invasion are significant parameters that can predict adverse clinical behaviors in PLGA/CASG on univariate analysis. Using the prior reported definition, an overlapping histology between PLGA and CASG was noted in over a third of the cases. Regardless of tumor subclassification, the percentage of cribriform and papillary patterns seems to be prognostically relevant and should be documented.