Case 51

This is a 8 yr old male, no significant PMH, presenting with enlarging mass on the left forehead. The patient was lifting up a chair two weeks ago when the chair happened to fall on top of his forehead, he did not lose conciousness and has not been complaining of a headache, however he began to have swelling at the site. A few days later he was playing with his cousin and was struck in the same area, again did not have LOC. However the swelling then began to worsen over the last 2 weeks. He states the swelling is not painful. Denies any fevers, headaches, nausea, vomiting, or neck pain. UTD on vaccines. Mother states he has otherwise been himself. Tolerating PO.

VS: T96.5 O, Pulse 102, BP 110/67, RR 20, SpO2 100%
Gen: Well-appearing, nontoxic, playful child.
Skin: Dry and warm, no appearance of rash. 2 cm x 2 cm x 1.5 cm left frontal scalp swelling noted, nontender to palpation, no fluctuance, no overlying erythema
Cardiac: S1, S2 present, RRR, no murmurs
Lungs: CTAB, no retractions
Abd: Soft, nontender, nondistended, normal bowel sounds

As you the provider begin to examine the patient, you take the ultrasound and use the linear probe to examine the swelling on the left forehead and this is what you see:

QUESTIONS

  1. What is your differential as you examine this mass?
  2. What the is normal architecture you should be seeing as you begin to scan in this location?
  3. When you see this finding, what other structure should you scan next with the ultrasound?
  4. What further imaging what you order to better delineate this finding?

ANSWERS

  1. In this short video, you see what appears to be a superficial cystic complex structure with multiple sepations within the swelling. The differential for this includes complex cyst, complex hematoma, or complex abscess. More commonly these could be pilar cysts which frequently occur on the scalp. In the setting of recent trauma this could also be a pyogenic granuloma, though that is uncommon on the face and usually presents with bleeding due to the formation of very friable tissue.
  2. Normally as you scan the scalp, you should see the superficial dermis and subcutaneous tissue, overlying a linear hyperechoic line representing the scalp and frontal bone. Here, this linear hyperechoic line is disrupted, indicating a likely depressed skull fracture in the setting of trauma.
  3. Since the swelling is on the left forehead, you should immediately scan the right forehead, to make sure that this abnormality you see is not a normal anatomical variant.
  4. A non-contrast CT Head should be ordered.

Upon using the ultrasound on this swelling, you immediately order a CT Head w/o contrast and obtain these images.

Diagnosis: Langerhans Cell Histiocytosis (LCH)

This rare disorder is caused by rapid proliferation of histiocytes, including lymphocytes, macrophages, and eosinophils, and is characterized by osteolytic lesions. In severe cases, these rapidly growing cells can infiltrate every organ in the body with exception of the heart and kidneys. Most typically, only one organ system is involved, with 77% of cases involving the bone, and most commonly the skull (40%). In 40% of cases, this may present with skin lesions, most frequently as brown/purple plaques or eczematous rash.

LCH can occur at any age but it is considered a pediatric disease, most commonly occurring between ages 1-3. Diagnosis and staging is made with tissue biopsies. Treatment for single system LCH of the frontal skull will include simple curettage of the bone lesions and topical skin therapy. Prognosis is very good, with extremely low rates of reoccurrence. Bone lesions of "CNS-risk" bones (sphenoid, orbital, ethmoid, or temporal bones) will include chemotherapy.