Presternal dermoid cyst mimicking lymphatic malformation: a case report and review of the literature

Midsternal bump: an infrequent localization of dermoid cysts

A 5-month-old boy was evaluated for an unusually large presternal bump present since birth. The ultrasound examination revealed a well-defined soft tissue mass with an oval shape. The lesion demonstrated a regular and well-demarcated outline, with an upper margin that was thinned and inserted into the upper skin plane; the content was anechoic with a small echogenic formation, mobile with changes in the patient's decubitus. The histologic diagnosis was dermoid cyst. Although dermoid cysts are commonly seen in the midline, the midsternal location, found in our patient, is rare. Dermoid cysts can have ultrasonographic features similar to those of other subcutaneous cystic masses. However, if an anechoic cyst with an internal well-circumscribed echogenic ball-like formation is seen within the presternal subcutaneous fat layer, as in our patient, dermoid cyst should be considered in the differential diagnosis of subcutaneous cystic masses.

Dermoid cyst in the subcutaneous tissues of the back: A rare case with multimodal imaging and pathologic correlation

Dermoid cysts are lined by keratinizing squamous epithelium and consist of skin appendages such as hair follicles, apocrine glands, and sebaceous glands. They are usually diagnosed during infancy or early childhood, commonly reported in the head and neck region. A dermoid cyst on the back is extremely rare, with only three cases in the pediatric and adult populations. We report a rare case of a dermoid cyst in the subcutaneous layer of the back in an adult. A 75-year-old man presented with a soft, painless mass on his left upper back. Computed tomography revealed a low-density mass nearly identical to the subcutaneous fat in the subcutaneous layer with nodular soft-tissue density components. It was a heterogeneously hyperechoic mass without internal vascularity on ultrasonography. On magnetic resonance imaging, the lesion showed nearly identical signal intensity (SI) to subcutaneous fat on T1 and T2-weighted images. The soft tissue component was intermediately hyperintense on T1- and T2- weighted images with enhancement. This lesion was pre-operatively suspected as a lipoma variant or a well-differentiated liposarcoma/atypical lipomatous tumor because of the fat density or SI and enhancing portion. We demonstrated and reviewed the multimodality imaging features of dermoid cysts at an unusual location and suggested imaging features that could help readers differentiate dermoid cysts from lipomatous tumors. When a mass shows fat density or SI with or without enhancing soft tissue components at the trunk or extremity, dermoid cysts as well as lipomatous tumors could be considered in the differential diagnosis.