1. HPI A 32 yo G2P2 woman presents to her PCP because of a lump that she felt on her lower belly. It is not painful but she thinks it has been growing in size over the past few months. She is concerned because there is a family history of colon cancer. She denies change in weight, fevers/chills/night sweats, nausea/vomitting, abdominal pain, and change in bowel movements. What else would you like to know?

2. PMH Medical Hx: C-section (2007, 2009), umbilical hernia repair (2011) Family Hx: Colon cancer (father, uncle, grandmother) Social: Married with 2 children, kindergarten teacher What is your differential diagnosis?

3. DDx Scar tissue (reactive fibrosis) Soft tissue tumor: desmoid, fibrosarcoma, lymphoma, neurofibroma Hemangioma Hernia What do you want to do next?

4. Physical Exam Vitals: BP 120/70, T 97.8, HR 70, RR 14 General: Patient is comfortable and cooperative HEENT, CV, Respiratory, Neuro, and Psych Exams: wnl Abdominal: bowel sounds present, no rebound/guarding, soft, no pain to palpation, firm and mobile mass in LLQ Skin: warm, dry, no discoloration or rashes present What tests do you want to order?

5. Tests CBC – normal – Check WBC to rule out lymphoma Pregnancy test – negative Imaging to evaluate mass: – Ultrasound – easy and inexpensive – CT or MRI – depending on u/s results Biopsy of mass for diagnosis

6. Abdominal Ultrasound Homogenous hypoechoic (dark) mass

7. Abdominal CT Well-circumscribed mass, usually homogenous – White arrow

8. Abdominal MRI Well-circumscribed mass – White arrow

9. Histology Spindle-shaped cells surrounded by collagen

10. Gross Specimen Well-defined capsule with collagen and fibrous sections

11. Overview of Desmoid Tumor “Aggressive fibromatosis” Fibrous, well-differentiated neoplasm originating from myofibroblasts Mutation of beta catenin Sporadic or associated with Gardner’s Syndrome

12. Overview of Desmoid Tumor Can arise in any skeletal muscle – Often the rectus abdominis Local infiltration can cause deformities and significant obstruction or compression Does not metastasize Histologically benign

13. Hallmarks of Desmoid Tumor Benign histology  bland fibroblasts

14. Hallmarks of Desmoid Tumor Post-partum or history of abdominal surgery Females > Men (~ 2:1) Typical patient is between 20 – 40 years old – Can occur in children and elderly

15. Associated Diseases Gardner Syndrome – Characterized by numerous colorectal polyps, osteomas, and soft tissue neoplasms – Autosomal dominant – 10-15% have desmoid tumors Bi-allelic APC mutation (“two-hit” hypothesis) – Subset of Familial Adenomatous Polyposis (FAP)

16. Treatment 1.Surgery – Surgical removal with negative margins is first-line treatment – Positive margins increase likelihood of recurrence 2. Radiation – adjunct or sole treatment 3. Chemotherapy – recurrent desmoid tumors

17. Pearls Desmoid tumor itself is benign but infiltration can cause morbidity Typical patient is post-partum woman in her 30s or female with previous abdominal surgery Recurrence rate is high (70%) Associated with Gardner’s Syndrome

18. Pearls American Cancer Society Colon Cancer Screening Guidelines – In general: colonoscopy at age 50 – Family Hx: colonoscopy at age 40 or 10 years earlier than youngest relative at age of diagnosis – FAP: annual flexible sigmoidoscopy starting at age 10 years and consider colectomy

19. Summary The patient is referred to a surgeon for removal of the desmoid tumor Due to her strong family history of colon cancer, she is scheduled for a colonoscopy and will consider being tested for the APC mutation so that she will know if her children are at risk