Pulmonary carcinosarcoma is a rare tumor within the sarcomatoid carcinoma group and consists of a mixture of malignant epithelial and sarcomatous mesenchymal elements such as cartilage, bone or skeletal muscle^1,2. It is found in the central or peripheral lung area¹. In general, the patients are in their 6th or 7th decade at the time of diagnosis and it is seen 4 times more commonly in males^1,3. Its development is closely related to smoking. Cases that are a result of asbestos exposure have also been reported^4-6. The most common epithelial component is reported to be squamous cell carcinoma (%45-70) and the mesenchymal component fibrosarcoma^1,7.

We report a male case who was found to have a mass in the lower part of the left lung and received a diagnosis of carcinosarcoma in this report and discuss the clinical and pathological features and the main points of differential diagnosis for this rare tumor.

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Figure 1: The chest X-ray of the case where the left hilar mass was detected.

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Figure 2: Left lower lobe heterogenous-density mass lesion with posterior location, compressing the thoracic anterior lobe on thoracic CT.

Macroscopically the material was 7.5x6.5x3 cm in size with a smooth surface and nodular character and was partially covered with visceral pleura. The sections showed that almost all the tissue was yellow-white with a solid character and fleshy consistency and consisted of tumoral lesions which were necrotic in some areas along with pulmonary tissue in a very small area at the periphery. Microscopic investigation showed that the tumor was well demarcated from the focal lung tissue in the periphery and that it consisted of necrotic areas and atypical pleomorphic cells with large nuclei where the nucleoli could be seen in many areas. Spindle tumor cell areas and focal chondroid differentiation areas were also observed. These cells also contained epithelioid cell groups containing keratinized cells in some areas and tumoral cell groups creating glandlike structures (Figure 3A,B,C). Immunohistochemical investigation showed that the epithelioid areas were strongly positive for PanCK (Figure 4A) and epithelial membrane antigen (EMA), focally positive for CK20 and P63 and negative for CK7. The epithelial markers were negative in the other defined tumoral areas whereas vimentin was diffusely positive (Figure 4B) and S-100 was positive in chondroid areas. Smooth muscle actin (SMA) and TTF-1 results were negative. These histopathological and immunohistochemical features led to a diagnosis of carcinosarcoma. There was no lymph node metastasis and the surgical stage was T3N0M0. The patient refused further treatment and is currently well on the 9th postoperative month with no progression on CT follow-ups.

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Figure 3: A) Tumor with dominant chondroid areas on the right and below, and epithelioid areas above (H&E; x100). B) Tumor cells with marked pleomorphism and atypia (H&E; x100). C) Areas of focal necrosis and neighboring epithelioid tumor cell groups (H&E; x200).

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Figure 4: A) Positivity of epithelioid cell groups with pan-keratin, B) Negative epithelial cells and widespread positivity in the sarcomatous cells with vimentin (DAB; x100).

Pulmonary carcinosarcomas are a quite rare sarcomatoid carcinoma type and are composed of malignant epithelial and mesenchymal components⁸. They have first been described by Kika⁶. The histogenesis is not clear and there are various theories. The commonly accepted view is that the epithelial and mesenchymal components are derived from the same histological origin and that the tumor is a biphasic monoclonal tumor⁹. Its development is closely associated with smoking but some cases following asbestos exposure have also been reported^4-6. It is mostly seen in male smokers older than 50¹⁰. Takeda et al.¹¹ have reported a male to female ratio of 4:1 while this ratio was 5.25:1 in the Cohen-Salmon et al.¹² study. Our case was a 74-year-old male smoker.

The clinical signs are related to tumor localization¹. Cabarcos et al.¹³ have reported the most common clinical sign as a cough and chest pain in their series of 48 pulmonary adenocarcinoma patients while other findings were “wheezing” due to bronchial obstruction, dyspnea, obstructive pneumonia or atelectasis. The radiological findings are nonspecific and similar to other pulmonary carcinomas⁷. Bull et al.¹⁴ have reported the endoscopic appearance in cases with a tumor extending endobronchially as a finger-like intraluminal extension. Our case had clinical symptoms of shortness of breath and a dry cough and the respiratory sounds were decreased on physical examination. The mass had obstructed the left lower lobe bronchus on bronchoscopy.

The value of preoperative diagnostic tests in defining the tumor is limited. Only one component of the tumor is seen during biopsy for centrally-located tumors while it may not be possible to reach peripherally-located tumors on bronchoscopy. Sputum cytology, bronchoscopic and transthoracic fine needle biopsy (TBFNA B) can sometimes aid the diagnosis. The chance of making a preoperative diagnosis with bronchoscopic biopsy or TBFNA B depends on endobronchial localization of the tumor. It is reported that TBFNA B can provide a diagnosis in large lesions that are located peripherally¹³. The bronchoscopic biopsy performed first in our case contained necrosis in most areas. The focal area neighboring the necrosis showed atypical pleomorphic cell groups that did not form definite patterns and these cells were positive with vimentin and negative with keratin. Following surgical resection, we saw that these cell groups belonged to one component of the tumor. The information above demonstrates the need to be careful when material with such features is encountered in biopsy material and to keep in mind the possibility of a biphasic tumor.

It is difficult to differentiate pulmonary carcinosarcoma from spindle cell carcinoma or blastoma and sarcoma metastatic to the lung with microscopy. Immunohistochemical investigations and/or electron microscopic findings play an important role in the differential diagnosis¹⁵. The definite diagnosis depends on histopathological and immunohistochemical findings¹⁶. It is reported that diagnosis can only be possible with multiple biopsies for cases with an endobronchial localization¹⁴. The macroscopic appearance of the tumor has been found to change depending on necrosis and hemorrhage⁷. Peripheral tumors are usually larger than 5 cm, have welldefined borders and a grey, yellow or cream-colored section surface and a mucoid or hemorrhagic consistency with prominent necrosis¹. Cases with a dominant sarcoma component have a solid consistency and grey color while those with a dominant carcinoma component are soft and friable⁷. The most common epithelial component is the squamous cell carcinoma (45-70%) followed by adenocarcinoma (31%) and adenosquamous carcinoma (19%)^1,8. The sarcomatous component usually consists of rhabdomyosarcoma, chondrosarcoma, osteosarcoma or a combination of these elements¹⁵. The section surface of the tumor in our case was yellow-white and contained occasional necrotic areas. Histologically, most of the tumor consisted of a sarcomatous component. The sarcomatous areas consisted of tumoral cells with occasional spindle character and focal chondroid differentiation areas and the carcinomatous areas had a morphological appearance consistent with squamous cell carcinoma and focal adenocarcinoma.

The most important prognostic parameter in sarcomatoid carcinomas is the tumor stage. They have a worse prognosis than classical non-small cell carcinomas even when grouped according to stage. It has been reported that adjuvant chemotherapy and radiotherapy are not helpful¹. The tumor has a marked tendency for distant metastasis and has a high rate of local recurrence. Postoperative survival is 9 months on average¹⁵. However, tumors with an endobronchial localization have been reported to have a better prognosis than peripherally located cases as they cause earlier symptoms¹⁷. There was no metastasis in the case we presented who is in his postoperative 9th month. He is still in good general condition and is being followed up.

In conclusion, pulmonary carcinosarcoma is a quite rare lung tumor. Finding tumor cell groups and performing advanced investigations are relatively easier on resection material than biopsy. However, it is a tumoral lesion where one must take into account the possibility of encountering small biopsy material that may contain only one component, which is usually the mesenchymal component.

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