Globally, lung cancer is a main cause of cancer-related mortality and morbidity related to cancer. Unfortunately, most cases are not detected and treated until the late stages of disease progression, and 50% of the patients present with established distant metastases. Common locations of distant metastases include the brain, bones, adrenal glands, and liver. However, metastasis to soft tissue, including skeletal muscles, is rare. In this case, we reported a rare presentation of gluteal muscle metastasis as the first complaint of primary adenocarcinoma of the lung in a 79-year-old man. Ultrasound revealed a right gluteal mass that raised the suspi-cion of an underlying occult malignancy. A histopathological evaluation also showed poorly differentiated adenocarcinoma (Immunophenotype: CK7+/TTF-1+/CK20-), favoring primary lung origin. Although soft tissue metastasis is a relatively rare site of distant spread, our case report underscores the need for a higher clinical sense and a lower threshold for biopsy, as these lesions might indicate an underlying hidden malignancy.

Globally, lung cancer is a main cause of cancer-related mortality and morbidity related to cancer. Unfortunately, most cases are not detected and treated until the late stages of disease progression, and 50% of the patients present with established distant metastases. Common locations of distant metastases include the brain, bones, adrenal glands, and liver. However, metastasis to soft tissue, including skeletal muscles, is rare. In this case, we reported a rare presentation of gluteal muscle metastasis as the first complaint of primary adenocarcinoma of the lung in a 79-year-old man. Ultrasound revealed a right gluteal mass that raised the suspi-cion of an underlying occult malignancy. A histopathological evaluation also showed poorly differentiated adenocarcinoma (Immunophenotype: CK7+/TTF-1+/CK20-), favoring primary lung origin. Although soft tissue metastasis is a relatively rare site of distant spread, our case report underscores the need for a higher clinical sense and a lower threshold for biopsy, as these lesions might indicate an underlying hidden malignancy.