Eur J Cardiothorac Surg 2005;28:775-777
© 2005 Elsevier Science NL
Myoepithelial carcinoma of the lung
Daiki Masuya
a
,
*
,
Reiji Haba
b
,
Cheng-long Huang
a
,
Hiroyasu Yokomise
a
a Department of Second Surgery, Faculty of Medicine, Kagawa University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-0793, Japan
b Department of Pathology, Faculty of Medicine, Kagawa University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-0793, Japan
Received 19 July 2005;
accepted 5 August 2005.
* Corresponding author. Tel.: +81 87 891 2191; fax: +81 87 891 2192. (Email: masuya{at}kms.ac.jp).
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Abstract
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Primary lung carcinomas showing features of salivary gland-type neoplasms are rare. Many are mucoepidermoid carcinomas and adenoid cystic carcinomas. Myoepithelial carcinoma of the lung is extremely rare, and in the WHO classification is classified as ‘Others’ among carcinomas of the salivary gland. The pertinent literature is restricted to a few pathological reports, and hardly any clinical examinations have been performed. Here we report a resected case of myoepithelial carcinoma of the lung, including details of clinical examination, with a review of previously documented cases.
Key Words: Myoepithelial carcinoma • Lung cancer • Salivary gland-type tumor
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1. Case report
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A 48-year-old man was admitted to our hospital because a routine chest X-ray examination had revealed a nodular shadow. Chest Computed Tomography (CT) demonstrated a 20x20-mm nodular shadow with an irregular border located in lateral basal segment of left lung. FDG-PET showed accumulation of FDG in an area corresponding to the shadow. TBLB via lateral basal segmental bronchus of left lung failed to give a definitive diagnosis, and therefore an open lung biopsy was performed because of suspected lung cancer. The tumor was elastic-hard measuring 15x15-mm and located in the peripheral lateral basal segment of left lung. Rapid intraoperative pathological examination diagnosed the tumor as malignant, possibly a sarcoma, sarcomatoid carcinoma, or carcinosarcoma. Left lower lobectomy (ND2a) was therefore performed concomitantly.
Pathological examination showed that the 15-mm tumor was continuous with the bronchial wall and projected into the bronchiole, resembling a polyp. The tumor cells mainly had oval nuclei and showed localized patches of proliferation (Fig. 1
a). Within the tumor, the cells showed marked nuclear swelling or irregularity, and five mitoses were evident per 10HPFs. Moreover, macronuclei and multinucleated cells were seen in some areas. The stroma was partially myxoid.
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Fig. 1. (a) The tumor cells mainly had oval nuclei and showed localized patches of proliferation (Hematoxylin and eosin stain; original magnification x100). (b) In ultrastructural findings, actin filaments with focal density were observed near the edge of the cytoplasm in parts of the cell.
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Immunohistochemical staining showed positivity for epithelial markers such as EMA, desmin, and cytokeratin 18. Vimentin, 
-smooth muscle actin (-SMA), and S-100, which are markers of smooth muscle, were also positive. 1-ACT, factor VIII, CD34, CD68, CD117, NSE and CEA were negative.
Ultrastructural examination revealed that the tumor cell nuclei were circular with abundant euchromatin and a conspicuous nucleolus. Actin filaments with focal density were observed near the edge of the cytoplasm in parts of the cell, indicating the presence of myoepithelial components (Fig. 1b). Scattered intercellular tight junctions and connecting structures were evident on the basilar membranes. On the basis of the above features, the tumor was diagnosed as a myoepithelial carcinoma.
The patient is currently doing well without recurrence at 15 months after surgery.
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2. Discussion
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Myoepithelial carcinoma generally arises from the salivary gland, the parotid, or the mammary gland, and is extremely rare in the lung [1]. Morphologically, it is easily confused with other entities. Myoepithelial carcinoma shows no duct formation, and often shows only myoepithelial differentiation. The present case was typical of this type. Furthermore, the tumor cells showed macronuclei, multiple nuclei, an increased frequency of mitosis, and a very high density of nuclear chromatin. Immunohistochemistry showed positive staining for cytokeratin, vimentin, S-100, -SMA, and GFAP, and ultrastructural examination demonstrated myoepithelial components such as actin filaments. Therefore, the tumor was diagnosed as a myoepithelial carcinoma. To our knowledge, only four cases of myoepithelial carcinoma of the lung have been reported in the English literature [2–4], although hardly any details of clinical examination were given. Therefore, we considered it important to document the clinical features of the present case in comparison with the previous ones.
The clinical characteristics of all five cases are presented together in Table 1
. With the exception of one case report that gave no details, the patients were men in the remaining four cases and aged between 46 and 58 years (mean 52.5 years). The tumor size ranged from 15 to 65 mm (mean 44.5 mm). Three of the tumors were located in the central bronchus, and one in the periphery. In the present case, FDG accumulation was observed in an area corresponding to the tumor, and dual time scanning confirmed an increased SUV in the delayed phase.
Although all cases were treated by at least lobectomy, postoperative metastasis to lymph nodes, the contralateral lung, the forearm, the lord part, and the liver was reported. Myoepithelial carcinoma of the salivary gland reportedly shows an aggressive clinical course in 50% of cases or more [5], and four of the five reported cases of lung myoepithelial carcinoma showed metastasis. The clinical course of those cases except ours was extremely poor. As clinical reports of lung myoepithelial carcinomas are extremely rare, further studies will be necessary in order to clarify their histological features, biological behavior, effects of chemotherapy or radiotherapy, and clinical outcome.
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References
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Abstract
1. Case report
