Intratumoral Heterogeneity of Subcutaneous Nodules in a Never-Smoker Woman of Lung Squamous Cell Carcinoma Detected on 18F-Fluorodeoxyglucose Positron Emission Tomography and Computed Tomography: A Case Report.

Subcutaneous tissue is a rare site of metastasis, accounting for only 1-2% of all lung neoplasms. Positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose (FDG) has been reported to increase the diagnostic accuracy of subcutaneous metastasis. A 58-year-old woman presented with complaints of dry coughing, in which three positive subcutaneous nodules were found on ¹⁸F-FDG positron emission tomography and computed tomography (PET/CT). Pathologic examination confirmed that each of the nodules contained 1) necrotic fat, 2) small amounts of blood cells and glandular epithelium, and 3) subcutaneous metastasis of moderately differentiated lung squamous cell carcinoma, respectively. Although PET/CT is useful for the detection of subcutaneous metastasis of primary lung cancer, we noted heterogeneous accumulation of ¹⁸F-FDG in subcutaneous tumors. This case highlights the importance of obtaining histological confirmation of malignant diseases whenever possible.