# Histiocytic Sarcoma Diagnosed on Repeat Biopsy of Multifocal Extranodal Tumors

## TL;DR

A rare case of histiocytic sarcoma was diagnosed after multiple biopsies of tumors in different parts of the body.

## Contribution

This case highlights the diagnostic challenges and importance of considering histiocytic sarcoma in multifocal extranodal tumors.

## Key findings

- HS was diagnosed after multiple biopsies showed non-specific findings initially.
- Multifocal extranodal tumors should include HS in differential diagnosis.
- Early diagnosis and intervention may improve prognosis in HS.

## Abstract

Histiocytic sarcoma (HS) is a rare malignant disease with a poor prognosis and unknown pathogenesis. In addition, this disease is difficult to diagnose due to the wide variety of diseases to be differentiated from it.

A 37-year-old woman with right-sided chest pain was referred to our hospital. Computed tomography (CT) revealed a 30-mm mass with osteolytic changes in the right eighth rib. Further examination revealed a rib mass, right renal mass, anterior mediastinal nodule, bilateral pulmonary nodules, and suprasellar nodule. A needle biopsy of the rib mass revealed granuloma with histiocytes. A subsequent needle biopsy of the right renal mass revealed similar findings without evidence of malignancy. The imaging findings suggested malignant disease; therefore, wedge resection of the upper lobe of the right lung and biopsy of the mediastinal mass were performed under general anesthesia. HS was diagnosed based on the immunostaining results.

For the treatment of HS, early intervention is said to contribute to a prolonged prognosis. In order to provide appropriate therapy, HS should be included in the differential diagnosis for multifocal extranodal tumors.