- Case Report
- Open Access
Benign pulmonary epithelial inclusions within the pleura: a case report
© Kenney et al; licensee BioMed Central Ltd. 2007
- Received: 11 June 2007
- Accepted: 29 June 2007
- Published: 29 June 2007
The normal visceral and parietal pleura are composed of a mesothelium-lined layer of fibrous connective tissue, consisting predominantly of collagen and elastin fibers, with interspersed nerves, lymphatics, and blood vessels. There is no normal epithelial component to the pleura, and the histologic finding of epithelial cells within pleural tissue typically indicates the presence of a malignant process. The one documented exception to this rule is the occasional occurrence of endometriotic implants, which can result in cyclic thoracic symptomatology and occasionally even hemothorax.
We present a case of seemingly benign epithelial inclusions within the pleura of a sixty year-old male patient who underwent exploratory thoracotomy and subsequent resection of bullous emphysematous blebs. Examination of the surgical specimen revealed well-defined nests of benign-appearing epithelial cells in glandular configurations at multiple sites within the pleura. These cells were immunopositive for TTF-1 and CK7 and immunonegative for calretenin, CK20, and CEA, indicating pulmonary epithelial derivation. Six months after resection, the patient is in stable health, with no clinical or radiologic evidence of bronchogenic carcinoma.
To our knowledge, this is the first report of benign pulmonary epithelial inclusions within pleural tissue. It is important to be aware that benign pleural inclusions occur, so as to avoid confusion with more serious processes in a population of patients who may have oncologic risk factors.
- Chronic Obstructive Pulmonary Disease
- Bronchogenic Carcinoma
- Mild Chronic Obstructive Pulmonary Disease
- Adenomatoid Tumor
Normal lung pleura is composed of fibrous connective tissue lined by mesothelium. While lymphatics, blood vessels, and nerves course within the pleural tissue, there is no normal epithelial constituent. Epithelial inclusions are occasionally seen in the form of endometriotic implants [1, 2]. However, the presence of epithelial cells in the pleura is typically indicative of a malignant process, such as direct involvement by primary lung carcinoma, pleural metastasis, or lymphangitic spread of a carcinoma. We present a case of benign epithelial inclusions of pulmonary derivation within the pleura.
We present the case of a 60 year-old male smoker with a history of chronic obstructive pulmonary disease (COPD) who presented with a two-week history of increasing shortness of breath and occasional wheezing. Review of systems was otherwise negative. Past medical history was remarkable for mild COPD, but the patient had otherwise been free of health problems. Physical examination of the chest revealed clear lung sounds bilaterally, and no other abnormal physical findings were evident. Chest x-ray demonstrated a right pneumothorax, and a subsequent CT scan confirmed a right pneumothorax (less than 10% of lung volume), a small right pleural effusion, and two large blebs in the right lung. No mass lesions were apparent. A nuclear medicine lung perfusion and ventilation scan showed retention of radiotracer consistent with COPD and heterogeneous patchy areas of perfusion, most likely related to air-trapping. It was decided to procede with surgical exploration and possible excision of the patient's emphysematous blebs. A right mini-thoracotomy was performed, and a large bleb was readily identified within the anterior chest, which was resected. A separate aarea of possible abscess was noted in the right apex, which on dissection by the surgeon contained yellow viscous fluid. Otherwise, no mass lesions or findings suspicious for carcinoma were encountered.
Six months after resection, the patient is in stable health, with no clinical or radiologic evidence of bronchogenic carcinoma. His respiratory status remains compromised secondary to chronic lung disease. We feel that the identified epithelial inclusions represent a benign process, likely associated with the background of chronic obstructive lung disease.
The pleural surfaces are subject to several pathologic processes which can result in the appearance of gland-like structures on histologic examination. Among malignant neoplasms, mesothelioma, bronchogenic carcinoma, and metastatic non-pulmonary carcinoma top the list [3–7]. Benign tumors also affect the pleura, including adenomatoid tumor and benign cystic mesothelioma [8–13]. However, relatively few benign processes have been shown to result in gland formation within the pleural tissue. The best documented example of such an entity is pleural endometriosis, which can result in endometrial gland and/or stromal deposition along or within the mesothelium [1, 2].
Benign "ectopic" glandular inclusions have been reported most frequently in the lymph nodes, and these structures can be either epithelial or non-epithelial. As in the pleura, nodal endosalpingiosis/endometriosis is the most common example and has been identified in up to 41% of pelvic and para-aortic lymph node excision specimens in females [14–18]. Other reported inclusions within the retroperitoneal and intraperitoneal lymph nodes have included those of colonic and pancreatic origin [19, 20]. Epithelial inclusions above the diaphragm are generally less common, but benign epithelial structures consisting of glandular breast tissue and squamous-lined cystic structures have been described in the axillary nodes [21, 22]. A somewhat more controversial topic is the existence of benign thyroid inclusions in cervical nodes, although several compelling examples have been presented [23, 24]. Non-epithelial inclusions are dominated by those composed of ectopic mesothelial cells which have been documented in the mediastinal and abdominal lymph nodes [14, 15, 25, 26]. Finally, examples of benign nevo-melanocytic lymph node inclusions and decidual implants have been reported [27, 28]. Examples of inclusions in non-nodal tissues are limited in number, but include peritoneal endosalpingiosis/endometriosis and surface epithelial inclusions of the ovary . Some argue that peritoneal benign cystic mesothelioma is also an example of a benign inclusion process .
The histogenesis of epithelial inclusions is not well-understood. Within the lymph nodes, two theories are proposed. The first invokes entrapment of epithelial cells during embryologic development, i.e. embryologic maldevelopment . The second is based on the concept of embolization, in which epithelial cells are exposed to and transported to lymph nodes via the lymphatics as a result of injury or inflammation . Once in the lymph node, the cells are able to survive in the local milieu. Nodal endometriosis is the prototype of this model, as the inflammatory process of menstruation may allow epithelial cells access to the lymphatics. In mesothelium-lines tissues, dysembryogenesis is still a possible explanation. However, two additional processes are also considered. The first involves direct spread of epithelial cells to the mesothelium in the setting of effusion and inflammation. Similar to the case in lymph nodes, the non-native epithelial cells would then survive in their new environment. The other explanation invokes metaplastic proliferation of epithelial cells from the mesothelial surface derived from embryonal coelomic epithelium or from subcoelomic mesenchyme [15–17]. The potential stimulus for this metaplastic change is not known, but as in other circumstances, chronic inflammation may play a role. Regardless of the histogenic nature of inclusions, their clinical significance comes at the time of microscopic examination, wherein they may be mistaken for primary or metastatic epithelial malignancies [15, 17, 23, 26].
The presented case represents the first report of benign pulmonary epithelial inclusions within the pleura. As in the examples above, the histogenesis of this process is not known. However, it may be surmised that chronic inflammation and/or fibrotic change in the setting of chronic lung disease may have contributed in some form, considering the patient's history of emphysema and subpleural fibrosis. The inflammatory millieu accompanying chronic lung disease and the process of repair, including secretion of growth factors such as PDGF, CTGF and TGF-Beta, may create a dysregulated environment suitable for abnormal stromal and epithelial proliferation. Alternatively, the glands may represent an unexplained metaplastic change or an example of embryologic dysregulation, leading to ectopic placement of epithelium. Simple entrapment of existing pulmonary tissue, however, seems unlikely, as the structures constitute well-formed glands rather than alveolar forms or other resident structures normally populating the most peripheral lung fields. Additionally, none of the several consulting pathologists who viewed this case were unable to convincingly explain their histologic appearance by simple entrapment. In fact, despite their relatively bland appearance, the presence of CK7 and TTF-1 positive glandular structures within the pleura raised concern for an occult lung carcinoma. However, there has been no clinical or radiologic evidence of malignancy in the patient thus far. Six months post-surgery he is in stable health and has exhibited no change in pulmonary symptomatology.
In summary, previous reports have described pleural epithelial inclusions consisting of endometriotic tissue, but there is no existing literature describing inclusions consisting of other benign epithelial tissues. In this case, benign pulmonary epithelial inclusions were incidentally identified histologically and confirmed by immunohistochemisical stains within the pleura of a sixty year-old male patient who underwent resection for bullous emphysema. The pathologist should be aware of the existence of such intrapleural structures, which may otherwise raise concern for a malignant process in patients with co-existing risk factors for bronchogenic carcinoma.
- Dhanaworavibul K, Hanprasertpong J, Cheewadhanaraks S, Buhachat R: Bilateral pleural endometriosis. J Obstet Gynaecol Res. 2006, 32 (1): 86-9. 10.1111/j.1447-0756.2006.00356.x.View ArticlePubMedGoogle Scholar
- Moffatt S, Mitchell J: Massive pleural endometriosis. Eur J Cardiothorac Surg. 2002, 22 (2): 321-3. 10.1016/S1010-7940(02)00277-4.View ArticlePubMedGoogle Scholar
- Allen T: Recognition of histopathologic patterns of diffuse malignant mesothelioma in differential diagnosis of pleural biopsies. Arch Pathol Lab Med. 2005, 129 (11): 1415-20.PubMedGoogle Scholar
- Allen T, Cagle P, Churg A, Colby T, Gibbs A, Hammar S, Corson J, Grimes M, Ordonez N, Roggli V, Travis W, Wick MR: Localized malignant mesothelioma. Am J Surg Pathol. 2005, 29 (7): 866-73. 10.1097/01.pas.0000165529.78945.dc.View ArticlePubMedGoogle Scholar
- Ohta Y, Shimizu Y, Matsumoto I, Tamura M, Oda M, Watanabe G: Retrospective review of lung cancer patients with pleural dissemination after limited operations combined with parietal pleurectomy. J Surg Oncol. 91 (4): 237-42. 10.1002/jso.20333. 2005, Sep 15Google Scholar
- Lee AH, Soomro IN: Collision tumour of the pleura composed of small cell carcinoma and malignant mesothelioma. Histopathology. 2003, 43 (4): 387-92. 10.1046/j.1365-2559.2003.01685.x.View ArticleGoogle Scholar
- Umezu H, Kuwata K, Ebe Y, Yamamoto T, Naito M, Yamato Y, Ishiyama T, Tsuchida M, Okuizumi M, Ishikawa H, Koizumi N: Microcystic variant of localized malignant mesothelioma accompanying an adenomatoid tumor-like lesion. Pathol Int. 2002, 52 (5–6): 416-22. 10.1046/j.1440-1827.2002.01357.x.View ArticlePubMedGoogle Scholar
- Kaplan M, Tazelaar H, Hayashi T, Schroer K, Travis W: Adenomatoid tumors of the pleura. Am J Surg Pathol. 1996, 20 (10): 1219-23. 10.1097/00000478-199610000-00007.View ArticlePubMedGoogle Scholar
- Ikuta N, Tano M, Iwata M, Ishiguro H, Nishiura T, Inagaki T, Suzuki S, Naitou Y, Takeuchi Y, Nakayama A: A case of adenomatoid mesothelioma of the pleura. Nihon Kyobu Shikkan Gakkai Zasshi. 1989, 27 (12): 1540-4.PubMedGoogle Scholar
- Haraguchi S, Koizumi K, Kawamoto M, Tanaka S: Video-assisted thoracoscopic excision of a benign cystic mesothelioma of pleura. Jpn J Thorac Cardiovasc Surg. 1998, 46 (8): 664-6.View ArticlePubMedGoogle Scholar
- Urbanczyk K, Skotniczny K, Kucinski J, Friediger J: Mesothelial inclusion cysts (so-called benign cystic mesothelioma) – a clinicopathological analysis of six cases. Pol J Pathol. 2005, 56 (2): 81-7.PubMedGoogle Scholar
- Sawh R, Malpica A, Deavers M, Liu J, Silva E: Benign cystic mesothelioma of the peritoneum: a clinicopathologic study of 17 cases and immunohistochemical analysis of estrogen and progesterone receptor status. Hum Pathol. 2003, 34 (4): 369-74. 10.1053/hupa.2003.31.View ArticlePubMedGoogle Scholar
- Sethna K, Mohamed F, Marchettini P, Elias D, Sugarbaker PH: Peritoneal cystic mesothelioma: a case series. Tumori. 2003, 89 (1): 31-5. ReviewPubMedGoogle Scholar
- Parkash V, Vidwans M, Carter D: Benign mesothelial cells in mediastinal lymph nodes. Am J Surg Pathol. 1999, 23 (10): 1264-9. 10.1097/00000478-199910000-00012.View ArticlePubMedGoogle Scholar
- Cohn D, Folpe A, Gown A, Goff B: Mesothelial pelvic lymph node inclusions mimicking metastatic thyroid carcinoma. Gynecol Oncol. 1998, 68 (2): 210-3. 10.1006/gyno.1997.4917.View ArticlePubMedGoogle Scholar
- Sheikh H, Krishnamurti U, Bhat Y, Rajendiran S: A 42-year-old woman with a 7-month history of abdominal pain. A, endometriosis involving ileocecal junction and 2 pericolonic lymph nodes; B, intranodal benign glandular inclusions. Arch Pathol Lab Med. 2005, 129 (12): e218-21.PubMedGoogle Scholar
- Chen K: Benign glandular inclusions of the peritoneum and periaortic lymph nodes. Diagn Gynecol Obstet. 1981, Fall;3 (3): 265-8.Google Scholar
- Horn L, Bilek K: Frequency and histogenesis of pelvic retroperitoneal lymph node inclusions of the female genital tract. An immunohistochemical study of 34 cases. Pathol Res Pract. 1995, 191 (10): 991-6.View ArticlePubMedGoogle Scholar
- Pages A, Ramos J: Ectopic intra-lymph node pancreas. Ann Pathol. 1982, 2 (3): 243-5.PubMedGoogle Scholar
- Perrone T: Embolization of benign colonic glands to mesenteric lymph nodes. Am J Surg Pathol. 1985, 9 (7): 538-41.View ArticlePubMedGoogle Scholar
- Fisher C, Hill S, Millis R: Benign lymph node inclusions mimicking metastatic carcinoma. J Clin Pathol. 1994, 47 (3): 245-7. 10.1136/jcp.47.3.245.PubMed CentralView ArticlePubMedGoogle Scholar
- Resetkova E, Hoda S, Clarke J, Rosen P: Benign heterotopic epithelial inclusions in axillary lymph nodes. Histological and immunohistochemical patterns. Arch Pathol Lab Med. 2003, 127 (1): e25-7.PubMedGoogle Scholar
- Leon X, Sancho F, Garcia J, Sanudo J, Orus C, Quer M: Incidence and significance of clinically unsuspected thyroid tissue in lymph nodes found during neck dissection in head and neck carcinoma patients. Laryngoscope. 2005, 115 (3): 470-4. 10.1097/01.mlg.0000157841.63283.87.View ArticlePubMedGoogle Scholar
- Meyer J, Steinberg L: Microscopically benign thyroid follicles in cervical lymph nodes. Serial section study of lymph node inclusions and entire thyroid gland in 5 cases. Cancer. 1969, 24 (2): 302-11. 10.1002/1097-0142(196908)24:2<302::AID-CNCR2820240213>3.0.CO;2-V.View ArticlePubMedGoogle Scholar
- Paull G, Mosunjac M: Fine-needle aspiration biopsy and intraoperative cytologic smear findings in a case of benign mesothelial-cell inclusions involving a lymph node: case report and review of the literature. Diagn Cytopathol. 2003, 29 (3): 163-6. 10.1002/dc.10325. ReviewView ArticlePubMedGoogle Scholar
- Sion-Vardy N, Diomin V, Benharroch D: Hyperplastic mesothelial cells in subpleural lymph nodes mimicking metastatic carcinoma. Ann Diagn Pathol. 2004, 8 (6): 373-4. 10.1053/j.anndiagpath.2004.08.009.View ArticlePubMedGoogle Scholar
- Burnett RA, Millan D: Decidual change in pelvic lymph nodes: a source of possible diagnostic error. Histopathology. 1986, 10 (10): 1089-92. 10.1111/j.1365-2559.1986.tb02545.x.View ArticlePubMedGoogle Scholar
- Patterson JW: Nevus cell aggregates in lymph nodes. Am J Clin Pathol. 2004, 121 (1): 13-5. 10.1309/JXE9-EYQX-D691-LV2Y.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.