P2.223: An Unusual Case of a Lump on the Head

Introduction: Cranial fasciitis (CF) is a rare disease found in the pediatric population characterized by benign fibroblastic hyperplasia involving the scalp and skull. First described in 1980, less than 100 cases have been reported to date. The etiology of CF is unknown, but it can be seen at birth or arise secondary to trauma or radiation exposure. Clinically, patients usually present with a single firm, non-tender, subcutaneous scalp mass characterized by rapid growth followed by a period of stabilization.

Case Description: A 5-year-old female presents to her pediatrician with a solitary bump on her scalp for 3 weeks first noticed while combing her hair. Review of systems is notable for intermittent constipation, but negative for scalp trauma, pain or interval growth of the lesion. On examination, she is well-appearing and tracking along previous weight and height trajectories. There is a 2 x 2-cm bony, non-tender lesion palpable over the left occipital prominence without overlying skin changes. A non-contrast computed tomography (CT) scan of her head reveals a 1.5 cm focal lytic lesion of the parasagittal left occipital bone concerning for osseous Langerhans cell histiocytosis (LCH) (see Figure 1 and 2). Labs to evaluate for multisystemic disease reveal normal complete blood count, normal electrolytes, and an elevated creatinine of 0.81 mg/dL. The elevated creatinine raises concern for LCH involving the kidneys; additional urine tests and renal ultrasound all return normal. A positron emission tomography (PET/CT) scan shows no hypermetabolic activity associated with the known lesion. Neurosurgery resects the bony mass; the pathology report shows dense fibroconnective tissue containing spindle-shaped fibroblasts within a collagenous matrix that is consistent with a diagnosis of CF. After the surgery, she makes a full recovery with no evidence of recurrence.

Discussion: CF and LCH are difficult to distinguish on CT because both typically present as an isolated osteolytic bone lesion. Further imaging with magnetic resonance imaging (MRI) could help distinguish LCH from CF and may reduce the need for excess whole-body radiation exposure from PET/CT scans. However, relying on imaging alone for a diagnosis can result in missing other rare malignancies (e.g., Ewing sarcoma, chondrosarcoma, etc). Complete surgical excision of the mass allows for confirmatory histopathological diagnosis and remains the first-line treatment for CF.

Conclusion: CF typically presents as a painless soft tissue mass that grows rapidly on the order of weeks to months. Tissue sampling is recommended to confirm the diagnosis. Overall, CF is benign and can be cured by surgical excision with a low risk of recurrence. Although there are isolated case reports describing spontaneous resolution of CF or resolution after treatment with intralesional steroids, further studies are needed to determine if more conservative management is equally as effective as surgical excision.