# Isolated skeletal Langerhans cell histiocytosis in adults: A case report

## TL;DR

This case report describes a rare instance of Langerhans cell histiocytosis in an adult, highlighting the challenges in diagnosis and treatment.

## Contribution

The paper presents a unique case of adult LCH with a satisfactory outcome despite deviating from standard diagnostic protocols.

## Key findings

- LCH in adults is rare and often misdiagnosed due to limited understanding.
- Invasive treatment before biopsy confirmation yielded satisfactory outcomes in this case.
- Excisional biopsy and curettage are effective for solitary LCH cases.

## Abstract

LCH in adults is rarely encountered, with the preference in children and axial skeleton as predilection site. Limited understanding of adult LCH causes frequent misdiagnosis, as our experience in an adult case of LCH threw off our differential diagnosis.

A 21-year-old male was referred to our hospital due to pain in his right shoulder. Plain radiograph and MRI showed a solitary well-marginated lytic lesion on the distal third of the clavicle. Together with a clear history and physical exam, the benign bone cyst was suspected and we performed an open biopsy simultaneously with curettage followed by internal fixation using a bone graft. Pathology and immunohistochemistry dismissed our suspicion and confirmed LCH as the main diagnosis. At six months post-surgery, no signs of recurrence were seen on the fixated site nor complained by the patient.

Diagnosing LCH involves considering imaging appearances and patient demographics as initial clues. However, confirming the diagnosis requires a biopsy with proven CD1 expression. Currently, the majority of studies recommend confirming the diagnosis before initiating therapy. This precaution is necessary due to the unclear pathophysiology of LCH, which complicates the implementation of specific therapies. Based on benign features of skeletal lesions found from imaging, invasive treatment before biopsy confirmation still gave a satisfactory outcome despite not being in line with the current recommendation.

Excisional biopsy and curettage in solitary LCH yield satisfactory outcomes. However, further studies are needed with larger sample sizes and interventional designs.

•LCH in adults is rarely encountered, with the preference in children and axial skeleton as predilection site.•Limited understanding of adult LCH causes frequent misdiagnosis.•Satisfactory outcomes were achieved by opting for invasive treatment before biopsy confirmation.

LCH in adults is rarely encountered, with the preference in children and axial skeleton as predilection site.

Limited understanding of adult LCH causes frequent misdiagnosis.

Satisfactory outcomes were achieved by opting for invasive treatment before biopsy confirmation.