Endobronchial ultrasound‐guided transbronchial needle aspiration diagnosis of mediastinal lymph node metastasis of mucinous adenocarcinoma: Arborizing stromal meshwork fragments as a diagnostic clue

Abstract

Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration (EBUS-TBNA) is a reliable and accurate method for the diagnosis of mediastinal metastases in patients with pulmonary and extrathoracic neoplasms. We report the cytopathologic findings of a case of metastatic signet-ring cell carcinoma with abundant extracellular mucin production in the mediastinal lymph nodes of a 41-year-old woman, who presented with nausea, abdominal pain, and weight loss. Imaging studies showed a renal mass, numerous lung nodules, and mediastinal and retroperitoneal lymphadenopathy. EBUS-TBNA of level 4R and 7 lymph nodes showed abundant, thick, "clean" mucus with entrapped ciliated bronchial cells, rare histiocytes, and fragments of cartilage. No neoplastic cells could be identified in Diff-Quik®-stained smears during the rapid on-site evaluation, but rare signet-ring cells were identified in the Papanicolaou-stained smears and cellblock sections. A distinctive feature of the aspirates was the presence of large branching (arborizing), "spidery" stromal fiber meshwork fragments. These stained metachromatically (magenta) with Romanowsky-type stains and cyanophilic to orangeophilic with Papanicolaou stains and showed occasional attached bland spindle cells, but had no capillary lumina or CD31-staining endothelial cells. The tumor cells were strongly and diffusely positive for CEA, CDX2, CK7, CK20, and MUC2, supporting the diagnosis of a metastatic signet-ring cell adenocarcinoma, most likely of gastrointestinal origin. We believe that the presence of the large spidery stromal fiber fragments is a useful clue to the presence of a mucinous neoplasm in EBUS-TBNA and allows the differentiation of the neoplastic mucus from contaminating endobronchial mucus.

Diagnostic utility of arborizing stromal meshwork fragments in mucinous tumors

“…Efforts to address this ongoing dilemma have been extensively explored in regards to the cytology of mucinous breast carcinoma and cystic pancreatic neoplasms . One study proposed that the presence of large embedded arborizing fragments of stroma (i.e., ASMFs) allowed distinction of neoplastic mucus from contaminating bronchial mucus in an EBUS‐TBNA of mucinous adenocarcinoma . We defined ASMFs as spidery extensions of metachromatic material on DQ‐stained smears with frayed edges and within a background of mucinous material.…”

“…[4][5][6][7][8][9][10] One study proposed that the presence of large embedded arborizing fragments of stroma (i.e., ASMFs) allowed distinction of neoplastic mucus from contaminating bronchial mucus in an EBUS-TBNA of mucinous adenocarcinoma. 12 We defined ASMFs as spidery extensions of metachromatic material on DQ-stained smears with frayed edges and within a background of mucinous material. In an archival analysis of 40 cases, including adenocarcinomas with mucinous features (29 cases), cystic mucinous neoplasms (4 cases) and 7 control cases, we sought to investigate the usefulness of ASMFs in cytology specimens.…”

“…In some body sites, such as pancreas, the distinction between well‐differentiated mucinous adenocarcinomas, cystic mucinous neoplasms with or without dysplasia, and gastrointestinal contamination can be difficult on EUS‐FNA, particularly with limited lesional cells, given the overlapping morphological features and low interobserver agreement . In the mediastinum and lung, differentiating mucin associated with a mucinous adenocarcinoma from contaminating bronchial mucus can also be a challenge . In one case report, the presence of arborizing stromal meshwork fragments (ASMFs) in EBUS‐TBNA was proposed as a useful clue to the presence of a mucinous adenocarcinoma .…”

“…[9][10][11] In the mediastinum and lung, differentiating mucin associated with a mucinous adenocarcinoma from contaminating bronchial mucus can also be a challenge. 3,12 In one case report, the presence of arborizing stromal meshwork fragments (ASMFs) in EBUS-TBNA was proposed as a useful clue to the presence of a mucinous adenocarcinoma. 12 The aim of this study was to review archival cytology cases with mucinous or mucoid material procured through different modalities to determine the diagnostic utility of ASMFs during rapid on-site evaluation (ROSE).…”

Cytologic features of pancreatic adenocarcinoma with “vacuolated cell pattern.” report of a case diagnosed by endoscopic ultrasound‐guided fine‐needle aspiration

“…In difficult cases, immunohistochemical stains may be useful to differentiate PDA with a vacuolated cell pattern from SRCC, which frequently show loss of membranous E‐cadherin and beta‐catenin expression . A panel of immunohistochemical stains including CK7, CK20, TTF1, CDX2, MUC1, MUC2, and estrogen receptor (ER) may be helpful in determining the primary site of metastatic SRCC …”