Rhabdomyomatous mesenchymal hamartoma presenting as a skin tag in the sternoclavicular area

Area of Science:

• Dermatology
• Pediatric Pathology
• Congenital Lesions

Background:

• Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare congenital skin lesion.
• Predominantly observed in newborns, with limited cases documented in English literature.
• Typically presents as a skin tag or mass on the face or sternal notch.

Observation:

• A 28-day-old infant presented with a soft skin tag in the right sternoclavicular area.
• The lesion measured 1.4 x 0.8 cm.
• No other congenital anomalies were noted on physical examination.

Findings:

• Shaved biopsy revealed a core of striated muscle fibers.
• The lesion also contained hair follicles, sebaceous glands, and eccrine glands.
• The exterior was lined by thin epidermis.

Implications:

• This case expands the known anatomical distribution of Rhabdomyomatous mesenchymal hamartoma.
• Highlights the importance of considering RMH in the differential diagnosis of congenital skin lesions.
• Contributes to the understanding of rare pediatric dermatological conditions.