# Metastatic squamous cell carcinoma of unknown primary: a case report and brief literature review

## TL;DR

This case report describes a rare cancer case where the primary tumor could not be identified despite extensive testing, highlighting the challenges in diagnosing and treating such cancers.

## Contribution

The report contributes a detailed case of squamous cell carcinoma of unknown primary and emphasizes the need for better diagnostic tools and collaborative research.

## Key findings

- Despite advanced imaging and genetic testing, the primary tumor site could not be identified.
- The patient achieved 14 months of disease-free survival after surgery and chemotherapy.
- The case highlights the limitations of current diagnostic methods and the need for comprehensive genomic profiling.

## Abstract

Carcinoma of unknown primary (CUP) is a rare malignancy characterized by metastatic disease without an identifiable primary tumor, even after extensive diagnostic evaluation. This case report described a 70-year-old female patient with squamous cell CUP (SCCUP) who initially presented with elevated carbohydrate antigen 19–9 and a diaphragmatic mass. Despite comprehensive workup, including 18F-fluorodeoxyglucose positron emission tomography–computed tomography and a 90-gene expression assay, the primary site remained unclear. The patient underwent surgical resection followed by two cycles of systematic therapy and achieved a disease-free survival of 14 months. This case underscores the limitations of the current diagnostic tools and the potential role of multimodal therapy in the management of CUP. The discordance between molecular testing and the clinical findings further emphasizes the perplexing nature of CUP. This report also reviews the literature on diagnosis and therapeutic options. Due to the absence of standardized regimens, future international collaboration and comprehensive genomic profiling are warranted to advance the understanding of this heterogeneous disease.