Metastasis of Rectal Signet Ring Cell Carcinoma to Typical Lipoma - A Rare Presentation of the Tumor-to-Tumor Metastasis Phenomenon

Sep 21, 2026

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Rectal signet ring cell carcinoma is an uncommon colorectal adenocarcinoma subtype with aggressive biology and poor outcomes. Tumor-to-tumor metastasis has been described, yet remains very rare. This case reports a 42-year-old man with rectal signet ring cell carcinoma whose surgery revealed an abdominal wall lipoma containing metastatic signet ring cell disease. Histopathology confirmed mucinous adenocarcinoma infiltrating fibroadipose tissue. The patient died 12 months after adjuvant chemotherapy from peritoneal progression.

LanguageEnglish

CategoryHealthcare

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Reading Time10 min

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Abstract

Introduction

Case Report

Presentation and Diagnosis

Imaging and Histopathology

Metastasis of Rectal Signet Ring Cell Carcinoma to Typical Lipoma: A Rare Presentation of the Tumor-to-Tumor Metastasis Phenomenon Journal of Investigative Medicine High Impact Case Reports Volume 12: 1–4 © 2024 American Federation for Medical Research DOI: 10. 1177/23247096241261309 [journals.sagepub.com/home/hic](journals.sagepub.com/home/hic) Houyem Mansouri, MD 1, Ines Zemni, MD2, Nedia Boujelbene, MD3, Fatma Saadallah, MD2, Mohamed Ali Ayadi, MD2, and Leila Achouri, MD 1 Abstract Rectal signet ring cell carcinoma represents a rare subtype of colorectal adenocarcinoma known for its aggressive biological nature and poor prognosis. Although the co-occurrence of colorectal carcinoma with other tumors has been reported, the uncommon phenomenon of tumor-to-tumor metastasis, first described in 1930, remains rare. The most frequent donor neoplasms are lung or breast carcinomas, whereas cerebral meningiomas have been reported to be the most frequent recipient neoplasms. Here we report a case of a typical lipomatous tumor harboring metastatic signet ring cell rectal carcinoma. It is about a 42-year-old man diagnosed with rectal signet ring cell carcinoma and treated with concurrent radiotherapy and chemotherapy followed by an anterior resection and manual coloanal anastomosis with a temporary ileostomy. During the surgery, an abdominal wall lipoma was discovered and excised. A histopathological examination revealed infiltration of the fibro adipose tissue by a mucinous adenocarcinoma with a contingent of signet ring cells. The patient died 12 months after adjuvant chemotherapy due to peritoneal progression. To the best of our understanding, this represents the initial documented instance of tumor-to-tumor metastasis from rectal signet cell carcinoma to a conventional nonvascular lipoma. Consequently, even if one of these tumors appears clinically and radiologically benign, it is prudent to entertain the prospect of tumor-to-tumor metastasis. Thus, a comprehensive pathologic study of both tumors is highly recommended. Keywords tumor-to-tumor metastasis, lipoma, rectal cancer, signet ring cell Introduction Colorectal cancer (CRC) is the world’s third most frequent cancer and the fourth leading cause of cancer mortality.1 Signet ring cell carcinoma (SRCC) is a rare histological form of rectal cancer, accounting for less than 1% of CRCs and about 1 .39% of rectal cancers.2 It is typically aggressive and has a poor prognosis. It most frequently metastases to the liver, lung, and central nervous system.3 However, metastases from CRC to another benign or malignant tumor, recognized as the phenomenon of “tumor-to-tumor metastasis,”are exceedingly uncommon. It represents a sign of poor prognosis and reflects the dissemination of the disease.4 Herein, we present a case of a colorectal signet cell carcinoma with the fortuitous discovery of a metastatic localization within a resected lipoma of the anterior abdominal wall. To the best of our knowledge, this represents the inaugural instance documented in the literature involving this specific pairing of a donor and a host tumor, and marks the initial occurrence of metastasis in a typical lipoma. Case Report A 42-year-old man, previously without any medical history, started complaining of sudden intermittent bloody stools, weight loss, and diarrhea. Despite these symptoms, he did not seek medical attention elsewhere until 6 months later, when he was referred to our center for evaluation. 1 Department of Surgical Oncology, Regional Hospital of Jendouba, Faculty of Medicine of Tunis, University of Tunis El Manar, Tunisia 2Department of Surgical Oncology, Salah Azaiez Institute, Faculty of Medicine of Tunis, University of Tunis El Manar, Tunisia 3Department of Pathology, Salah Azaiez Institute, Faculty of Medicine of Tunis, University of Tunis El Manar, Tunisia Received March 4, 2024. Revised May 19, 2024. Accepted May 27, 2024. Corresponding Author: Ines Zemni,

FAQs

What makes this rectal cancer subtype clinically important?

Rectal signet ring cell carcinoma is rare and typically aggressive, associated with poor prognosis.

What rare phenomenon is highlighted in the case?

Tumor-to-tumor metastasis, specifically metastasis from rectal signet ring cell carcinoma into a typical nonvascular lipoma.

How was the metastasis discovered and confirmed?

An abdominal wall lipoma was found and excised during surgery; histopathology showed mucinous adenocarcinoma with signet ring cells infiltrating the lipoma.

Sep 21, 2026

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