Abstract
Sir, Primary sarcomas of the lung account for less than one percent of all malignant pulmonary tumors.[1] Radical surgical resection is the treatment of choice.[2] These tumors may metastasis to lymph nodes and other viscera via the lymphatic or hematogenous route. The skeletal metastasis in these tumors is extremely rare.[3] We present a rare case of primary undifferentiated spindle cell sarcoma of the lung that later developed metastasis to bone, without lymph node metastasis. A fifty three year old gentleman presented with a two-month history of dull aching, progressive pain on the left side of the chest, cough and a single episode of hemoptysis. A chest radiograph showed a radio-opaque lesion in the left upper lobe of lung. Contrast enhanced computed tomography (CECT) of the chest revealed a large well defined mass in the upper lobe of left lung [Figure 1a]. Fibreoptic bronchoscopy revealed a growth in the left upper lobe bronchus. The bronchoscopic biopsy revealed highly atypical mainly spindle shaped tumor cells, with areas of necrosis. Immunohistochemically, the tumor cells were diffusely positive for vimentin and were negative for a wide panel of epithelial markers and other markers such as p63, TTF1, smooth muscle actin (SMA), desmin and S100-P. Diagnosis of a sarcomatoid carcinoma was preferred over a sarcoma. The tumor was staged with whole body PET-CT scan and magnetic resonance imaging (MRI) brain [Figure 1b]. There was no evidence of metastasis elsewhere in the body. We approached the tumor through a left postero-lateral thoracotomy and complete resection of the tumor with systematic mediastinal lymph node dissection was done. Gross examination showed a 6.8 × 5.8 × 5.5 cm tumor with grey-white cut surface with areas of necrosis. Microscopic examination showed a sarcomatoid tumor, mostly composed of spindly cells with areas of coagulative tumor necrosis. Diagnosis of spindle cell sarcoma was offered with closet differential of synovial sarcoma. Translocation studies were negative (SYT-SSX, SYT-SSX1), thus diagnosis of a primary undifferentiated spindle cell sarcoma of lung was offered.Figure 1: Pre operative imaging. (a) CECT of thorax showing large well defined mass in the upper lobe of left lung. (b) Whole body PET scan showing an isolated large FDG avid mass in upper lobe of the left lung without evidence of any distant metastasisPostoperatively, the patient was treated with five cycles of adriamycin and ifosfomide based chemotherapy. He was asymptomatic till one year post-surgery, when he developed pain in his left hip joint. An MRI scan of the pelvis showed an increased signal to the left iliac bone extending to the acetabulum with a large, cystic lesion in the left iliopsoas muscle [Figure 2a]. PET-CT imaging revealed destruction of the left iliac bone with multiple FDG avid lung nodules [Figure 2b] suggestive of lung and skeletal metastases. The iliac bone biopsy showed high-grade spindly sarcomatous cells, consistent with metastases from spindle cell sarcoma. The patient was treated with best supportive care and died fifteen months after the index surgery.Figure 2: Imaging showing distant metastasis. (a) CT of thorax showing bilateral pulmonary metastasis. (b) MRI of the pelvis, coronal section, showing skeletal metastasis in left Ilium with lager intra and extra pelvic soft tissue component (black arrow)Primary undifferentiated sarcomas are rare mesenchymal tumors that more commonly affect the musculoskeletal system. Primary visceral involvement, especially of the lung by undifferentiated sarcomas is very rare. Our patient had a primary spindle cell sarcoma of the lung and later developed metastasis in the left iliac bone which was diagnosed on PET CT and confirmed with biopsy. This is extremely unusual and an exhaustive literature search revealed no cases of primary undifferentiated spindle cell sarcoma of lung with skeletal metastases without lymph node involvement. High grade or poorly differentiated spindle cell sarcomas that do not display any specific lineage are currently termed as spindle cell undifferentiated/unclassified sarcomas. In present case, synovial sarcoma was considered as the closest possibility, despite negative epithelial markers. Synovial cell sarcoma is characterized by a specific chromosomal translocation t (X; 18) (p11; q11).[4] Our case RTPCR analysis was done but it did not reveal the specific transcript. Thus, a final diagnosis of an undifferentiated spindle cell sarcoma was concluded. PET CT scan is a useful investigation that rule out extra pulmonary malignancy in patients with a pulmonary sarcoma. Lucas reported a sensitivity and specificity of FDG PET of 73.7% and 94.3%, respectively for detection of local disease.[5] They suggested that FDG PET could identify both local and distant recurrence of tumor as a one-step procedure and detect other sites of metastases. Treatment consists of surgical excision, but prognosis remains poor due to a high incidence of local and distant metastases. The present case displayed pulmonary metastasis, followed by bony metastasis that is further a rare clinical presentation in this uncommon tumor, leading to a fatal disease course.