JuniperPublishers-Skeletal Muscle Metastasis from Non Small Cell Lung Cancer (NSCLC) a Rare Case Report

Journal of Surgery- JuniperPublishers

Introduction

Skeletal muscle metastasis is a rare condition resulting from non small cell lung cancer. We present a case of 50 yrs old male who presented with a mass in left thigh that was attached to sartorius muscle in left thigh. It was completely removed and the patient is doing well after four years of surgery.

Case Report

A 50 –year-old male, diagnosed case of adenocarcinoma of the lung (NSCLC) who completed the course of chemotherapy and radiations, presented with a swelling in left thigh. It was painless and increasing in size over the last one month. He didn’t show any abnormality on systematic review. Left thigh showed localized swelling over upper medial aspect oval, 5*6 cms, non tender, Non- fluctuant, hard without any change in overlying skin. Radiologic evaluation on MRI showed lobulated mass measuring 4.7*4.5 cms closely related to superficial femoral neurovascular bundle and involving sartorius muscle .The mass showed homogenous T-2 hyper intensity and moderately intense contrast enhancement with internal septae. Mass was inseparable from the superficial femoral artery and nerve (Figures 1 & 2).

U/S guided biopsy of the mass showed fragmented biopsy consisting of sheets of atypical cells with vesicular nuclei, prominent nucleoli and pale eosinophilic to clear cytoplasm occasional mitotic figures seen. Immunohistochemistry showed positive staining for BerEP4,CK7 ,CK19 and EMA .The appearances were consistent with moderate to poorly differentiated metastatic adenocarcinoma. Patient underwent surgical excision of the mass in April 2008.Tumor was extending into the quadriceps muscle and invading the fibers of femoral nerve which were removed. It was however dissected freely out of the femoral vessels. Frozen section confirmed carcinoma and posterior margin free of tumor. Patient made uneventful recovery without any neuro-vascular deficit.

Patient developed swelling again in the same region just one month after the surgery, the investigations of which showed soft mass. He underwent surgical excision of the recurrent mass that showed sac like structure filled with soft pasty material. Histopathology of this revealed an organized hematoma, without any evidence of malignancy. His whole body PET-CT done in Oct 2009 showed no recurrence of the disease in left thigh, although he develops recurrent seroma at this site which responded to multiple aspiration in the clinic. His latest follow up with us in Sep’2011 showed no recurrence at the site of surgery and patient was doing well.

Discussion

Skeletal muscle metastasis in a cancer patient is a rare phenomenon [1], and its reported incidence is 0.8-1 % [2-6]. Due to muscular contractility, high tissue pressure [7] local pH environment and accumulation of lactic acid and other metabolites skeletal muscle metastasis (SMM) is rarely found. In order of frequency lung carcinoma is the leading cause of SMM followed by tumors of kidney, pancreas, thyroid gland, breast, ovary, prostate and bladder cancers [1,8,9]. Analyzing cadaver muscles of patients died of cancers Pearson [4] found skeletal muscle metastasis in 16 % of the cases. SMM of primary lung tumor are rare and literature includes few reports [1,3,10]. Histologically SMM may present as nodules or infiltrates. Presence of neoplastic vascular emboli may suggest a hematogenous spread [4].

The most frequent presentation is muscular pain with or without swelling [9,10]. Our patient is exception as he presented with a painless swelling of left upper thigh. One case of Intra muscular metastasis from lung cancer presenting as intra muscular abscess has been reported [11]. Diagnosis of this condition can be difficult even with radiological investigations as these can be confused with an abscess or soft tissue tumor [12]. In CT hypodense lesion, sometimes calcified, is seen and normally fat and vascular architecture is blunted [13]. Whole body PET-CT detects unexpected extra thoracic metastasis in 10-20 % of patients with NSCLC and changes therapeutic management in approximately 20 % of the patients [14-16].

Treatment is palliative only as surgical excision, radiotherapy and chemotherapy all are employed [1,10,12]. Regardless of surgical or medical therapy presence of skeletal muscle metastasis is associated with poor survival of less than one year [1,5,10,12]. Our patient is still surviving without any complications after four years of surgical resection. The onset of muscle pain resistant to medical therapy, in patients of lung cancer should raise the suspicion of skeletal muscle metastasis and thorough diagnostic workup is necessary including MRI, PET-CT, U/S, FNA and surgical exeresis. Optimal strategy is unknown and presence of SMM does not modify the regimes of chemotherapy and radiations.

Conclusion

Skeletal muscle metastasis is a rare occurrence in non small cell lung cancer. Treatment is palliative only and options are surgical excision, radiotherapy and chemotherapy of metastatic deposit. Prognosis is poor despite all modalities of treatment.

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