11/27/2007 Case 1: Langerhan cell histiocytosis

Clinical History:

An 18-month-old girl presented with a subcutaneous mass in the right occipital region. Her parents noticed that the mass had enlarged over the previous several weeks. They reported that the child was happy, playful, and eating well. She walked and babbled words, showing ageappropriate development. She had no history of fevers, weakness, or seizures. An ultrasound reportedly showed a subcutaneous lesion possibly eroding the underlying skull and a "dermoid or "epidermoid tumor" was suspected. Examination by a pediatric neurosurgeon was normal. On palpation the mass was movable, soft and compressible with a solid component and it was located inferior to the occipital protuberance. MRI showed a 2.2 x 2.8 x 3.1 cm lobulated midline-toright occipital mass involving soft tissue and skull with intracranial
extension. It was isodense on T1 weighted sequences, slightly heterogeneous on T2, and demonstrated heterogeneous enhancement with gadolinium. Additional masses were present in the right infratemporal fossa (2.7 cm) with extension along the right sphenoid wing and near the sphenoid ridge (1 cm). Significant clinical laboratory values:
Alk phos = 272, Ca2+ = 10.3, LD = 284, one month after presentation. Surgery performed a few weeks later disclosed a "pseudocapsule to tumor made of pericranium."

Diagnostic Notes:

Histologically, this was a classic case with large, pale tumor cells with large, folded or indented nuclei and inflammatory cells including many eosinophils. CDla immunostaining as well as Birbeck granules ultrastructurally were important for diagnosis of Langerhans cell histiocytosis (LCH) , that the new WHO classification refers to as the most common of the dendritic cell-related disorders. The new WHO brain tumor book also mentions that "LCH is currently classified on the basis of extent as unifocal, multifocal (usually polyostotic) and disseminated disease." Either CDla or Birbeck granules are required for diagnosis. The differential diagnosis of pediatric skull lesions was discussed and most are benign cysts.

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