A case of Langerhans cell histiocytosis of the skull in which preoperative methionine positron emission tomography was useful in comprehending the spreading of the lesion
A 20-year-old female.\nNo major illnesses.\nThe patient consulted our institute after becoming self-aware of swelling and dull pain in the left side of her head from 3 months prior.\nShe was clearly conscious and no symptoms of neurologic deficit were observed. A soft flexible tumor was palpated in an approximately 3 × 3 cm region on the left side of her head and tenderness at that site was observed.\nThere were no inflammatory findings and the tumor marker was within the normal range.\nAn oval radiolucent line was observed in the left cranium upon simple head X-ray []. A slightly heterogeneously enhanced tumor in left parietal bone was observed inside the bone defect in a gadolinium-enhanced T1-weighted image upon head magnetic resonance imaging (MRI); wherein, the dura mater and subcutaneous tissue contacting the tumor widely exhibited an enhancing effect and was found to have thickened [Figure and ]. Nuclide accumulation was observed in the tumor inside the bone defect upon FDG-PET; however, the brain cortex accumulation was also high in the area adjacent to the brain surface, so the border was unclear, making evaluation difficult []. No significant abnormal accumulations in other areas of the body were observed. Meanwhile, such accumulation was observed to be poor in the center of the tumor upon Met-PET, while accumulation with a well-defined border was observed in the border as well as the dura mater and subcutaneous tissue adjacent thereto [].\nAccordingly, it was believed to be an extramedullary tumor such as LCH of the skull, meningioma, malignant lymphoma, etc. The tumor was symptomatic and enlarged within a relatively short period of time; therefore, surgery was carried out including pathological diagnosis.\nA U-shaped skin incision was made on the left side of the head. When the skin flap was reversed, the subcutaneous tissue was strongly adhered to the defective part of the bone. A craniotomy was carried out leaving a distance of approximately 3 cm from the defective part of the bone such that the range observed with accumulation upon Met-PET was sufficiently included [Figure -]. When the bone flap was reversed, the tumor was observed to be yellow in color. The tumor was adhered to the dura mater and the dura mater of the attachment site was yellow in color and particularly thick. The dura mater was excised, while leaving a border of approximately 1 cm from the thickened part of the dura mater [Figure -]. Tumor cells were not observed in the stump of the excised dura mater upon immediate pathological examination. The subcutaneous tissue adhered to the defective part of the bone was also resected and the excised stump was negative. The defective part of the bone was excised upon providing a border of approximately 1 cm [], and this was supplemented using artificial bone Biopex®. The defective part of the dura mater was sutured using artificial dura mater (GoreTex®).\nThe accumulation of tumor cells having a nuclear groove and constricted nucleus in the border part observed with accumulation upon Met-PET was observed inside the extracted skull [Figure -]. The tumor cells were immunohistochemically positive for CD1a, DEC205, and Langerin. The center part with poor accumulation lacked tumor cells, with fibrous tissue accounting for most parts []. Accordingly, it was diagnosed as LCH. The dura mater was observed to have undergone invasion of histiocyte-like tumor cells and eosinophil similar to the tumor itself in the region corresponding to the accumulation region upon Met-PET [Figure -]. Tumor cells and inflammatory cells were not observed in the dura mater stump.\nThe course was good and the patient was discharged without any deficiency symptoms. Relapse has not been observed as of 7 months following surgery.