Differential Diagnosis for a Small Soft Tissue Mass on the Head of a 4-Month-Old Along the Parietal Scalp

• Single Most Likely Diagnosis
  • Caput succedaneum or cephalohematoma: These are common conditions in newborns, resulting from birth trauma. However, they can still be present or become noticeable a few months after birth, especially if they are small and not immediately diagnosed. Justification: The location on the parietal scalp and the age of the child make these conditions plausible, as they are directly related to the birthing process and can evolve over time.
• Other Likely Diagnoses
  • Dermoid cyst: A congenital anomaly that can present as a soft tissue mass. Justification: Dermoid cysts can occur anywhere on the body, including the scalp, and are known to be present at birth, though they may not be immediately noticeable.
  • Hemangioma: A benign vascular tumor that can appear as a soft mass. Justification: Hemangiomas are common in infants and can appear on the scalp, often growing rapidly before eventually involuting.
  • Lipoma: A benign tumor composed of fat tissue. Justification: Though less common in infants, lipomas can occur at any age and may present as a soft, movable mass.
• Do Not Miss Diagnoses
  • Neuroblastoma metastasis: Although rare, neuroblastoma can metastasize to the scalp, presenting as a mass. Justification: This diagnosis is critical to rule out due to its potential for severe outcomes if not promptly treated.
  • Langerhans cell histiocytosis (LCH): A rare disorder that can cause soft tissue masses. Justification: LCH can present with skin lesions or masses, among other symptoms, and requires early diagnosis for effective management.
  • Rhabdoid tumor: A rare, aggressive tumor that can occur in the scalp. Justification: Given its aggressive nature and poor prognosis, it's crucial to consider this diagnosis to ensure timely intervention.
• Rare Diagnoses
  • Encephalocele: A rare congenital defect where brain tissue and meninges protrude through a skull defect. Justification: While rare, an encephalocele could potentially present as a soft tissue mass, especially if it is small and covered by skin.
  • Teratoma: A type of tumor that can contain several different types of tissues. Justification: Teratomas are rare in the scalp and more commonly found in other areas of the body, but they could potentially present as a soft tissue mass.
  • Fibromatosis colli: A rare condition characterized by a mass in the neck, but very rarely could present in other areas. Justification: This condition is typically associated with the neck, but considering its nature as a fibrous mass, it's conceivable, though highly unlikely, to find it in other locations.