Dermoid cyst of the left upper limb: A common case in a rare site

An 83-year-old male patient had undergone surgical removal of a mass in his left upper arm 5 years ago, but its specific diagnosis was unknown. Two years ago, the mass recurred. The mass was associated with pain, redness, swelling, and elevated skin temperature for a month. Palpation revealed a soft mass and plain magnetic resonance imaging (MRI) showed an oval-shaped mass with an abnormal signal behind the triceps at the proximal end of the left upper arm, with a size of 6.5 × 7.4 × 12.5 cm, and equal or slightly low signal on T1-weighted images and mixed high signal on T2-weighted and short tau inversion recovery images. There were multiple hairline, flocculent, low-intensity lesions on short tau inversion recovery images, with low-intensity surrounding the lesion on each sequence and adjacent muscles appearing pushed and deformed. Multiple lymph nodes in the left axilla were enlarged, and no abnormal signals were found in relation to the left humerus (Fig. 1A–D). A dermoid cyst was diagnosed based on pathological examination (Fig. 2). Fig. 2 View Large Image Figure Viewer Download Hi-res image