Benign Umbilical Tumors Resembling Sister Mary Joseph Nodule.

Background: When physicians see an umbilical nodule, most of them instinctively recall the Sister Mary Joseph nodule. Therefore, dermatologists need to recognize umbilical dermatoses that can be mistaken for the Sister Mary Joseph nodules. This study aimed to describe the different kinds of benign umbilical tumors as well as elucidate the factors that can be used to distinguish the Sister Mary Joseph nodule from these tumors.

Methods: The "benign umbilical tumor" group included 19 patients, whereas the "Sister Mary Joseph nodule" group comprised 30 patients (2 from our department, 28 from PubMed search). We compared the clinical and dermoscopic findings between 2 groups.

Results: In the "benign umbilical tumor" group, the most common diagnosis was dermatofibroma (5/19), followed by keloid (3/19), and soft fibroma (3/19). These tumors had various colors (red, brown to black, and flesh colored) and exhibit characteristic surface changes (eg, verrucous changes in epidermal nevi and verrucae). Conversely, most Sister Mary Joseph nodules have an erythematous color, oozing or ulceration on the surface, and nearby satellite lesions. Furthermore, the dermoscopic findings of Sister Mary Joseph nodules showed a polymorphous vascular pattern and a white or milky-red, amorphous area. Benign lesions showed different dermoscopic patterns: pigment networks with white areas (dermatofibromas), thrombosed capillaries (verrucae), and the "pore sign" (epidermal cysts).

Conclusions: Various cutaneous tumors can be mistaken for the Sister Mary Joseph nodule when they develop on the umbilicus; the clinical and dermoscopic differences found in this study may be useful for establishing a differential diagnosis.