# Cancer of Unknown Primary With Squamous Cell Carcinoma Phenotype Presenting as Isolated Axillary Mass

## TL;DR

A 71-year-old woman with a family history of breast cancer was diagnosed with a rare cancer type after presenting with an isolated axillary mass.

## Contribution

This case highlights the diagnostic challenges of cancer of unknown primary with a squamous cell carcinoma phenotype.

## Key findings

- The patient had a strong family history of breast cancer but was diagnosed with a rare metastatic squamous cell carcinoma.
- The axillary mass biopsy revealed poorly differentiated squamous cell carcinoma with no identifiable primary tumor.
- The case emphasizes the importance of considering rare cancers in differential diagnoses despite confounding clinical history.

## Abstract

Cancer of unknown primary (CUP) is a rare metastatic malignancy where no primary tumor can be found. We report the case of a 71-year-old female with a strong family history of breast cancer presenting with isolated axillary lymphadenopathy after a tick bite. A biopsy of the axillary mass revealed poorly differentiated squamous cell carcinoma and after extensive evaluation, she was diagnosed with metastatic squamous cell carcinoma with unknown primary tumor. We present this case because of the role of confounding history complicating her initial diagnosis and bringing awareness to a rare disease.