Pulmonary tumor diagnosed as an undifferentiated sarcoma with epithelioid features: a case report

Background Pulmonary sarcomas are uncommon accounting for 0.5 % of all primary lung cancers. Undifferentiated sarcomas account for up to 20 % of soft tissue sarcomas. A lung tumor revealed to be an undifferentiated sarcoma with epithelioid features has never been reported in the literature. Case presentation A 61-year-old white Moroccan man presented with 2 months’ history of hemoptysis and dyspnea. Chest computed tomography showed a cystic mass involving the lower field of his right lung evoking first a hydatid cyst. Abdominal computed tomography revealed bilateral adrenal nodules. Surgical resection of the lung mass was performed. On pathological examination, the tumor was cystic containing necrotic material. A histological diagnosis of undifferentiated sarcoma with epithelioid features was made. A positron emission tomography scan showed involvement of his pleura, left colon, adrenal glands, left thigh muscle, and leptomeninges. Conclusions Undifferentiated sarcoma with epithelioid features is a rare malignant mesenchymal tumor. Clinical and radiological features are not specific. A differential diagnosis includes sarcomatoid carcinoma, malignant mesothelioma, melanoma, and other epithelioid sarcomas.


Background
Pulmonary sarcomas are uncommon accounting for 0.5 % of all primary lung cancers. Undifferentiated sarcomas (US) are a heterogeneous group of malignant mesenchymal tumors that do not meet criteria for a welldefined histopathologic entity [1,2]. They account for up to 20 % of soft tissue sarcomas and occur at all ages and anatomic sites with no difference between the sexes [1]. Clinical and radiological features are not specific. On morphologic examination, US is divided into pleomorphic, spindle cell, round cell, and epithelioid subsets [1]. Cases of US with epithelioid features (USEF) are rarely reported in the literature [3]. We describe the first case of a lung tumor revealed to be a USEF.

Clinical history
A 61-year-old white Moroccan man with no significant past medical history presented to Mohamed V Military Hospital with hemoptysis and dyspnea which developed 2 months before admission.
A positron emission tomography (PET) scan, performed subsequently on the 28th day after surgery, visualized foci of increased 18 F-fluorodeoxyglucose ( 18 F-FDG) uptake in his lung tumor (Fig. 4), left colon, adrenal glands, left thigh muscle (Fig. 5), and leptomeninges. A colonoscopy was normal. He is undergoing anti-mitotic chemotherapy.

Discussion
US are a heterogeneous group of malignant mesenchymal tumors that do not meet criteria for a well-defined histopathologic entity [1,2]. It is a diagnosis of exclusion that accounts for 20 % of sarcomas [1]. US occur at all ages and anatomic sites with no difference between the sexes [1,3]. Most reported cases are pleomorphic. The epithelioid variant has been rarely reported. Sarcomas of the lung are mainly metastatic [4]; primitive pulmonary   [5].
Clinical and radiological features of sarcoma are not specific and sometimes asymptomatic [1,6]. The macroscopic findings are not distinctive but tumoral necrosis is frequent [1]. On morphologic examination, USEF is composed of nests of cells with amphophilic cytoplasm and large vesicular nuclei [1]. USEF lacks specific immunohistochemical abnormalities; tests for vimentin are positive and tests for smooth muscle actin are sometimes positive [7]. Tests for CKs, desmin, EMA, CD99, and CD34 are generally negative [1]. The differential diagnosis includes sarcomatoid carcinoma, malignant mesothelioma, melanoma, and other sarcomas such us epithelioid sarcoma, leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, epithelioid hemangioendothelioma, dedifferentiated liposarcoma, synovial sarcoma, and metastatic epithelioid gastrointestinal stromal tumor [1,4,6].
The treatment of USEF is similar to epithelioid sarcoma [3]. In localized form, the treatment is based on surgical excision followed by adjuvant doxorubicinbased chemotherapy and sometimes radiotherapy [3]. The treatment of metastasizing tumors is based mainly on chemotherapy. The prognosis of USEF is poor and the 5-year survival is 52 % [3]. Recurrences and metastases occur in 25 % and 35 % of cases respectively [3].

Conclusions
In summary, USEFs are extremely rare malignant sarcomas. They can occur at all ages and anatomic sites. The epithelioid variant has been rarely reported. The diagnosis is based on morphological and immunohistochemical analyses that allow exclusion of differential diagnoses. In our case, the location posed additional diagnostic difficulties.