# Multifocal Extramedullary Plasmacytoma of the Thyroid With Cervical and Paratracheal Lymph Node Involvement and Progression to Multiple Myeloma

## TL;DR

A rare case of thyroid plasmacytoma progressing to multiple myeloma is reported, highlighting the need for careful monitoring and new treatment strategies.

## Contribution

This case report documents a rare progression from thyroid extramedullary plasmacytoma to multiple myeloma.

## Key findings

- Extramedullary plasmacytoma of the thyroid with cervical and paratracheal lymph node involvement was diagnosed.
- The disease progressed to multiple myeloma despite initial negative systemic workup.
- Treatment with chemotherapy and stem cell transplant showed favorable response.

## Abstract

Extramedullary plasmacytomas without evidence of systemic illness make up less than 5% of all plasma cell neoplasms. The incidence of extramedullary plasmacytoma of the thyroid region is exceedingly rare. This report discusses the case of a 72-year-old male with extramedullary plasmacytoma of the thyroid. The patient underwent a total thyroidectomy for an enlarging right-sided thyroid nodule, and intraoperatively, the plasmacytoma was found to have an extracapsular component with adherence to the regional soft tissue as well as involvement of the right laryngeal nerve and regional lymph nodes. Despite a comprehensive negative workup for multiple myeloma initially, including a bone marrow biopsy and hematologic workup, the disease progressed to multiple myeloma following definitive radiation therapy, as evidenced by the development of hypermetabolic lytic lesions and further pathological examination. The patient’s treatment course included systemic chemotherapy and an autologous stem cell transplant, resulting in a favorable treatment response. The progression to multiple myeloma despite established guidelines highlights the need for close observation and the potential for innovative therapeutic strategies to manage this rare entity.