# An Unusual Case of Lynch Syndrome

## TL;DR

A 69-year-old woman with no family history presented with unusual symptoms leading to the discovery of a colorectal tumor and possible Lynch syndrome.

## Contribution

Highlights an atypical clinical presentation of Lynch syndrome with delayed diagnosis and non-gastrointestinal initial symptoms.

## Key findings

- Lynch syndrome was suspected based on immunohistochemistry despite non-classical symptoms.
- The patient presented with a large abscess and necrotizing fasciitis linked to an undiagnosed colorectal tumor.
- Histological analysis confirmed invasive adenocarcinoma with high-grade dysplasia.

## Abstract

Lynch syndrome is the most common cause of hereditary colorectal cancer. It usually develops asymptomatically until symptoms related to colorectal carcinoma appear, such as gastrointestinal bleeding, abdominal pain, and changes in bowel habits and/or stool characteristics. Oftentime, when these clinical signs and symptoms are not present, the diagnosis becomes challenging. We present the clinical case of a 69-year-old woman, adopted, with no known previous history, who presented to the emergency department with low back pain, without irradiation, that had been going on for three days, associated with inflammatory signs in the right hip region. There were no urinary or sensory alterations and no recent trauma. She was initially discharged with antibiotherapy with the diagnosis of hip cellulitis. As the symptoms continued and the inflammation spread to the right lower limb, she returned to the emergency department. A CT scan revealed an abscess (17 cm) in the right buttock, complicated by necrotizing fasciitis due to fistulization from a tumor in the right colon. She underwent an exploratory laparotomy, which identified a neoplasm of the ascending colon, adherent to the abdominal wall, in the right lumbar region. Right hemicolectomy and drainage of the right buttock/thigh abscess were performed. The histology was compatible with invasive adenocarcinoma, with high-grade dysplasia but well differentiated, pT3G1N0. The immunohistochemistry was suggestive of Lynch syndrome.