# Idiopathic Pulmonary Fibrosis Comorbid With Mediastinal Small Cell Carcinoma: A Clinical Dilemma

## TL;DR

A rare case of mediastinal small cell carcinoma combined with idiopathic pulmonary fibrosis presents complex diagnostic and treatment challenges.

## Contribution

This case highlights the lack of existing data on managing comorbid idiopathic pulmonary fibrosis and mediastinal small cell carcinoma.

## Key findings

- The patient's mediastinal mass decreased with chemotherapy and radiation, but IPF continued to progress.
- Prednisone and mycophenolate mofetil showed modest responses, but anti-fibrotic therapy was ineffective.
- No prior cases address the management of both conditions together in this rare patient cohort.

## Abstract

We present an interesting case of mediastinal small cell carcinoma (MSCC), an exceedingly rare entity, comorbid with idiopathic pulmonary fibrosis (IPF). A 66-year-old female was first seen in the pulmonology office for abnormal chest computed tomography (CT) findings of right apical bronchiectasis and subpleural fibrotic changes with focal pleural thickening along the fissures, along with a right lower lobe nodule. Pulmonary function testing (PFT) showed an obstructive pattern with modest bronchodilator response, although subsequent PFT showed a worsening restrictive pattern with a worsening DLCO. On a follow-up CT one year later, a soft tissue density with peripheral calcification was found in the anterior mediastinum, later found to be hypermetabolic on a PET scan. Radiographically, fibrosis worsened with the appearance of worsening diffuse bilateral coarse reticular interstitial changes with lower lobe predominance, honeycombing, and areas of ground-glass opacity. A biopsy of the mediastinal lesion showed a high-grade neuroendocrine tumor. Cam5.2, insulinoma-associated protein-1, synaptophysin, and thyroid transcription factor-1 immunostains were positive. She underwent four cycles of chemotherapy with cisplatin and etoposide with a total of 60 Gy of radiation. Mediastinal mass started to decrease in size. Her respiratory status, imaging, and PFTs continued to show evidence of IPF progression. Prednisone resulted in modest clinical and radiographic response. Steroid-sparing therapy with mycophenolate mofetil, although effective, had to be discontinued due to GI bleeding. Anti-fibrotic therapy was deferred due to evidence showing a lack of clinical improvement. We discuss the existing evidence available on IPF management and proceed to highlight the deficiencies in existing data available on the management of IPF and MSCC in these patients. Most of the cases of MSCC reported in the past have managed MSCC using guidance from treatment practices for small cell lung cancer. No reported cases discuss or describe the management of IPF and MSCC in the very rare cohort of patients our case represents.