Langerhans cell histiocytosis (LCH) is a rare disease that represents a clonal proliferation of pathologic Langerhans cells [1]. Although its clinical manifestations range from isolated bone lesions to multisystem disease, the pathological finding is uniform irrespective of the disease manifestation. Besides their characteristic morphology, Langerhans cells are further identified histochemically by the presence of the CD1a and S-100 surface markers and electro-microscopically by the presence of Birbeck granules [2]. Pathological findings are obligatory for diagnosis. LCH usually occurs in young children with a peak from 1 to 4 years [3]. Soft tissue involvement is usually the secondary extension of an adjoining primary bone lesion, while the secondary involvement of an adjacent bone by a primary soft tissue LCH lesion is rare [4]. Here, we report the case of a 17-month-old Asian male child with a solitary primary soft tissue LCH lesion in the right forehead area with secondary bone destruction by indentation. This 17-month-old male child was referred to our institution for a forehead mass that rapidly enlarged in three weeks. This child initially presented at an outside clinic, and an ultrasonographic (US) evaluation was performed. The US revealed a soft tissue mass with a diameter of 22 mm and with bone erosion and destruction on the right forehead. LCH was suspected, and the patient was referred to our institution. Initial recognition of the mass was at three weeks before admission. Physical examination revealed a 3.0×3.0 cm tender and fixed mass over the right forehead. Computed tomography (CT), fluorodeoxyglucose positron emission tomography (18F-FDG-PET)/CT, and skull radiography imaging studies were performed before open surgery (Figs. 1, ,2).2). In December 2011, the mass was extirpated under general anesthesia. On the operative field, we observed an irregularly shaped firm mass measuring 2×3 cm, located in the subcutaneous layer with periosteal inflammation and thinning of the frontal bone without dural exposure. To reconstruct the thinning of the frontal bone, we performed an allograft with a demineralized bone matrix and an osteoconductive bone void filler. Pathologic findings showed that under high magnification (×400), the tumor cells were mostly large monocytes with abundant cytoplasm and occasionally central grooved nuclei, admixed with numerous eosinophils. The presence of Langerhans cells was confirmed by CD1a and S-100 immunohistochemistry (Figs. 3, ,4).4). To identify whether the tumor origin was the soft tissue and the bone, we conducted a pathologic study of the adjoining periosteum. The histologic study revealed mild chronic inflammation with fibrosis; this result confirms the diagnosis of primary soft tissue LCH. After surgery, this child was followed-up at Samsung Medical Center every 6 months with a bone scan (Fig. 5), and the 1-year follow-ups were conducted at our institution. During the follow-up period of 3 years, no evidence of recurrence was found. LCH, previously known as histiocytosis X, is a histiocytic disorder of unknown etiology that is characterized by the clonal proliferation of dendritic cells in various organs and tissues. LCH has a variable clinical presentation and course, ranging from a solitary, often spontaneously resolving, bone lesion to a fatal multicentric and multiorgan system disease. LCH lesions can involve any organ in the body; however, bones, skin, and lungs are the most common sites of involvement. Soft tissue involvement is usually due to the extension of an adjoining primary bone lesion [4]. In our case, LCH with a soft tissue origin affected the adjoining bone by indentation. Before surgical exploration, the origin of the mass was difficult to identify on the basis of radiologic findings. To identify whether the tumor origin was the soft tissue or the bone, we conducted a pathologic study of the adjoining periosteum. The histologic study revealed mild chronic inflammation with fibrosis; this result confirmed the diagnosis of primary soft tissue LCH. There are multiple treatment modalities for LCH: solitary, easily accessible lesions can be surgically extirpated, and intralesional corticosteroid application and radiotherapy are also possible options [5]. However, clinical guidelines for the treatment of LCH are still under development. In our patient, timely surgical extirpation of the mass was performed and no evidence of recurrence was found during the 3-year follow-up period. Here, we presented the case of a 17-month-old child with a solitary primary soft tissue LCH lesion, which influenced the adjacent bone by indentation. Due to the rarity of LCH that involves both the soft tissue and the bone, it is difficult to identify the tumor origin. In this case, LCH with an ambiguous origin was completely resolved by surgical extirpation, and the primary soft tissue origin of the tumor was confirmed by a histologic study.
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Open Access
Oct 17, 2017
Erin M Gibson + 2
