The Differential Diagnosis of Squamous Cells in Pancreatic Aspirates: From Contamination to Adenosquamous Carcinoma

Abstract

Background: This study was conducted to describe the frequency and significance of squamous cells in fine needle aspiration (FNA) specimens of the pancreas in benign and malignant processes. Methods: A retrospective review was performed of 102 patients with squamous cells in their pancreatic FNA specimens from 1986 to 2012. The malignant cases were classified as adenosquamous carcinoma (ASqC) or metastatic squamous cell carcinoma, and a double institutional review of the ASqC cases was undertaken to characterize the clinical and pathological features and survival statistics of patients who present with unresectable or metastatic ASqC and have no follow-up surgery. Survival analyses were performed. Results: Of the 4,094 pancreas FNA procedures performed in the study, squamous features were found in 102 (2.5%) of all cases, and 48% of these cases represented ASqC. The other cases were contamination (52%) or atypical (<1%). ASqC constituted 4.5% (46/1,025) of all primary pancreatic exocrine malignancies. When compared with conventional adenocarcinoma, ASqC demonstrated a significantly poorer overall median survival (11.0 vs. 6.51 months; p = 0.023), and this difference was also seen in patients presenting with metastatic disease (median survival of 9.1 vs. 4.2 months; p = 0.025). Conclusions: Squamous cells in FNA specimens from the pancreas have a broad differential diagnosis that ranges from contamination to ASqC.

Adenosquamous carcinoma of the pancreas: Molecular characterization of 23 patients along with a literature review

“…The pathology of ASCP includes the typical squamous carcinoma pattern that is characterized by epithelium with whorls, keratohyalin, or pearls [14,16] , as seen in Figure 1. Compared to nuclei of benign squamous cells, the nuclei of malignant squamous cells are hyperchromic and pleomorphic [15,22] . The squamous carcinoma component of ASCP appears to be more focal in the tumor.…”

“…Normal pancreas tissue has no benign squamous epithelial components [9,15,22] . Various hypotheses have been proposed regarding the histogenesis of ASCP.…”

“…There is a transitional zone where the glandular structure blends into the squamous component [22] . There is an entity descriptive of pure squamous cell carcinoma of the pancreas, but this classification has been debated and is considered to be more secondary to metastasis to the pancreas from a non-pancreas primary carcinoma [15,25,26] . Tumor cell necrosis is frequently seen in patients with ASCP, along with high tumor grade [25,27] .…”

“…The mean tumor diameter in one series of resected ASCP patients was 46.3 mm vs 33.5 mm of adenocarcinoma pancreas patients (P value 0.0001) [11] . Comparisons between patients at single institutions and matching for stage have yielded an overall median survival of 6.51 mo vs 11.0 mo for ASCP vs adenocarcinoma [15] . In another large single institution analysis of patients with ASCP, the median survival of patients with resection was 10.9 mo, which was worse than those with pancreatic adenocarcinoma who underwent resection, which was 17.9 mo [16] .…”

“…Adenosquamous histology is seen in cancers of other organ systems such as lung, esophagus, colon, stomach, salivary glands, and the female reproductive system [20] . Compared to pancreatic adenocarcinoma, which has a poor 5-year overall survival, survival is worse in patients with ASCP [12][13][14][15] . The etiology of ASCP is unknown.…”