LAUSR

cT4NxM1b1). The patient received local palliative radiation therapy and chemotherapy with platinum/pemetrexed (Fig. 1B1 and B2). The third case was a 73-year-old man receiving active treatment guided by sensitivity testing results for documented Mycobacterium xenopi infection. Positron emission tomography showed a lesion measuring 40 × 25 mm with central cavitation in the left upper lobe (SUVmax 28.38) (Fig. 1C) and a hypermetabolic focus located in the left iliopsoas muscle with SUVmax 13.43, suggestive of MSM. In all 3 cases, histological specimens were obtained for characterization, and the results were consistent with high grade undifferentiated tumor, striated muscle infiltrated with adenocarcinoma, and squamous carcinoma, respectively, all originating in the lung. The clinical progress of the patients differed: death 2 weeks after diagnosis, pain control, and reduced tumor size (Fig. 1B2) after targeted oncological treatment; clinical stabilization was achieved in the last 2 cases described. Given the low prevalence of MSM, a detailed differential diagnosis that includes the more common malignant and benign entities (sarcomas, primary muscle lymphomas, and myxomas/hemangiomas) must be made. Although no clinical guidelines are available for the specific management of MSM, treatment is based on general oncological principles guided by clinical picture, site, and life expectancy, and approaches include observation, surgical excision (persistent solitary lesions after a period of remission), chemotherapy and radiation therapy (useful for pain control and for the reduction of tumor size).2–4 The correct identification of MSM in LC patients is essential for clinical management and prognosis. For this reason, the possible neoplastic etiology of any muscle lesion, whether symptomatic or not, detected in LC patients must be evaluated with combined radiological procedures and histological confirmation of the lesion. References