# Primary pleural small cell carcinoma with massive pleural effusion: A rare case report

## TL;DR

A rare case of primary pleural small cell carcinoma is reported, highlighting its aggressive nature and the importance of accurate diagnosis and timely treatment.

## Contribution

This case report presents a rare instance of primary pleural small cell carcinoma diagnosed via pleural effusion analysis.

## Key findings

- The tumor was confirmed via immunohistochemical markers and showed a Ki-67 index of >90%.
- Chemotherapy led to a partial response, indicating potential for disease control with prompt intervention.
- Effusion cytology with cellblock proved effective for accurate diagnosis of this rare tumor.

## Abstract

Lung cancer is the leading cause of cancer-related mortality worldwide, with small cell lung carcinoma (SCLC) accounting for significant morbidity and mortality. While SCLC typically arises from neuroendocrine cells in the central lung, primary pleural small cell carcinoma is exceedingly rare. Its atypical presentation poses diagnostic challenges, emphasizing the need for early recognition and accurate diagnosis to optimize outcomes.

A 70-year-old male presented with progressive shortness of breath and significant weight loss. Imaging revealed massive pleural effusion. Pleural fluid analysis via pleurocentesis, including cytological evaluation and cell block analysis, revealed features consistent with small cell neuroendocrine carcinoma. Immunohistochemical studies confirmed the diagnosis, with tumor cells positive for pancytokeratin, TTF1, synaptophysin, and INSM1, and negative for Napsin-A, p40, WT1, calretinin, and chromogranin. A Ki-67 proliferation index of >90 % indicated a highly proliferative tumor. Chemotherapy with Carboplatin and Etoposide was initiated, leading to a partial response as evidenced by follow-up PET-CT imaging.

Primary pleural small cell carcinoma is an exceptionally rare and aggressive variant of SCLC. Accurate diagnosis relies on cytological and immunohistochemical analyses to differentiate it from other pleural malignancies, particularly mesothelioma. The high Ki-67 index indicates its aggressive nature. Management follows conventional SCLC protocols, with systemic chemotherapy as the primary treatment modality. The patient's partial response highlights the potential for disease control with prompt intervention.

This case highlights the rarity and aggressive nature of primary pleural small cell carcinoma. Advanced diagnostic techniques and timely treatment are critical.

•Unlike typical SCLC, which originates in the central lung, primary small cell carcinoma of the pleura arises in the pleura•Effusion cytology with cellblock is an effective tool to diagnose this aggressive tumor type accurately.•Early diagnosis is the key to management as it shows a very aggressive clinical course.

Unlike typical SCLC, which originates in the central lung, primary small cell carcinoma of the pleura arises in the pleura

Effusion cytology with cellblock is an effective tool to diagnose this aggressive tumor type accurately.

Early diagnosis is the key to management as it shows a very aggressive clinical course.