Benign Mesothelial Cells in Mediastinal Lymph Nodes

Abstract

Inclusions of benign tissues in lymph nodes are most often aberrant glandular tissue, including endosalpingiosis, the thyroid, parotid, breast, and pancreas. Nonglandular inclusions are rare and include nevus cells and decidua. Mesothelial cells in lymph nodes are exceedingly rare; only eight cases have been reported in mediastinal lymph nodes and three cases in abdominal lymph nodes. The incidence of benign mesothelial cells in mediastinal lymph nodes in patients with a history of pericarditis or pleuritis is reported in this study. A retrospective search showed eight cases with removal of mediastinal lymph nodes in the absence of neoplasm. Hematoxylin and eosin-stained sections were examined in all cases. Immunohistochemical stains for CAM 5.2 were performed in all cases, and stains for AE1/AE3, Ber-EP4, carcinoembryonic antigen, Leu-M1, B72.3, and S-100 were performed in one case. CAM 5.2-positive cells with features of mesothelial cells were present in five of eight cases. In all cases, the cells were present in nodal sinuses and appeared as single cells or small clusters. The cells were missed on routine hematoxylin and eosin sections in all cases but one, in which they were numerous and mimicked metastatic carcinoma. Malignancy was not found in any of the cases preoperatively, at the time of surgery, or during the follow-up period. Benign mesothelial cells may embolize to regional lymph nodes in pleuritis or pericarditis. In most cases, these cells are few and undetectable on routine sections. Rarely, hyperplastic mesothelial cells may be present and must be distinguished from metastatic carcinoma, mesothelioma, and melanoma.

Benign mesothelial cells as confounders when cytokeratin immunohistochemistry is used in sentinel lymph nodes

“…Benign mesothelial cells in draining lymph nodes have been described in intrathoracic [2,3], mesocolic [4], and abdominal [5] locations. In the intrathoracic lymph nodes, benign mesothelial cell deposits are rare [2] and are almost always found in association with inflammation of the serosal surfaces, such as in our case.…”

Stellenwert von Cytokeratin- und CA19–9-Antigen im immunhistologischen Nachweis disseminierter Tumorzellen in Lymphknoten beim Pankreascarcinom

“…Unter der von Parkash et al beschriebenen Voraussetzung, dass der Cytokeratinnachweis sowohl sensitiv als auch spezifisch für disseminierte Tumorzellen ist [25], wurde anschlieûend ein Cytokeratin-Antikörper eingesetzt.…”

“…Im Gegensatz dazu zeigen unsere Resultate mit dem Antikörper gegen CA19±9, dass nicht jeder tumorassoziierte Antigennachweis in Lymphknoten tatsäch-lich mit einem Carcinomgeschehen in Verbindung stehen muss. Hingegen wurde die gewählte Methode des Cytokeratinnachweises bereits als sehr sicher beschrieben [25]. Interessanterweise sind in 13 Jahren nur 11 Fälle beschrieben worden, bei denen mesotheliale Zellen ohne Vorhandensein eines malignen Tumors in Lymphknoten gesichert wurden [25].…”

“…Hingegen wurde die gewählte Methode des Cytokeratinnachweises bereits als sehr sicher beschrieben [25]. Interessanterweise sind in 13 Jahren nur 11 Fälle beschrieben worden, bei denen mesotheliale Zellen ohne Vorhandensein eines malignen Tumors in Lymphknoten gesichert wurden [25]. Allerdings ist eine ektope Produktion von Cytokeratinproteinen sowie die ektope oder illegitime mRNA-Expression von Cytokeratin in mesenchymalen Zellen nicht vollständig auszuschlieûen [32,39].…”

Benign Müllerian inclusions coexisting with breast metastatic carcinoma in an axillary lymph node

“…Their importance relies on the differential diagnosis with metastatic carcinoma. Many types of inclusions have been reported, including salivary gland and breast tissue, squamous epithelium, thyroid follicles, mesothelial and melanocytic cells [5,8], and Müllerian-type epithelium [8]. So called Müllerian inclusions are found almost exclusively in women and mainly in pelvic lymph nodes; their appearance is very similar to peritoneal endosalpingiosis and, like endosalpingiosis, they can mimic metastasis from ovarian carcinoma.…”