Sporadic Right Lumbar Intraabdominal Desmoid Tumor: A Case Report

Abstract

Sporadic intraabdominal desmoid tumor is a rare occurrence, comprising 0.03% of all neoplasms. It has an estimated incidence of 2 to 4 per million in the general population. Only 15% of all desmoid tumors are intraabdominal. Often, they are present with abdominal distension or bowel obstruction symptoms. Desmoid tumors are not readily differentiated from others through computed tomography (CT) scans. We are sharing a case of a young (34-year-old) patient who presented with tender palpable right lower quadrant mass. The CT scan shows a well-defined intraperitoneal mass over the right lumbar region. Limited right hemicolectomy was done. Histopathology shows features consistent with desmoid tumors. Surgical excision remains the mainstay of treatment, though various nonsurgical treatments have been described with promising results. Our case of sporadic intraabdominal desmoid tumor was managed with surgical resection.

 

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Keywords

fibromatosis - aggressive - desmoid disease - colorectal neoplasms

Introduction

Desmoid tumor is also known as aggressive fibromatosis, being considered a benign neoplasm that does not metastasize but is locally invasive. It can rapidly increase in size and cause mass effects on surrounding structures. It is a rare stromal tumor that comprises only 0.03% of all neoplasms, and only accounts for < 3% of all soft tissue tumors.[1] The estimated incidence of desmoid tumors in the general population is about 2 to 4 per million. It is significantly higher among those with familial adenomatous polyposis (FAP) which is nearly 3%.[2]

Desmoid tumors have been reported to arise from many different sites. They can be classified into abdominal (60%), extra- (25%), and intraabdominal (15%).[3] They are more commonly found at the abdominal wall and extraabdominal sites. These tumors are more likely to be intraabdominal when associated with FAP and Gardner's syndrome.[1] In sporadic cases of desmoid tumors, intraabdominal tumors only account for 5% of cases.[1] Otherwise, they are rarely found in these organs or in the mesentery.[4] Intraabdominal desmoid tumors often present with distensions or bowel obstructions associated with tumor growth or invasion.[3] Demographically, desmoid tumors are most commonly found between 25 and 35-years-old.[2] They are more predominant among the female population.[2]

In general, computed tomography (CT) scans offer a good preoperative differential diagnosis and assessment of patient with intraabdominal desmoid tumor.[1] However, the definitive diagnosis of such tumor is a tissue biopsy obtained via core biopsy or excision of the tumor itself.

 

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Case Report

A 34-year-old gentleman presented with the complaint of chronic and progressive worsening right lower quadrant abdominal discomfort for 6 months. He was a chronic smoker with no significant medical illness except for a history of left open hernioplasty for uncomplicated left inguinal hernia 9 years prior to his presentation. Otherwise, there were no symptoms of altered bowel habits, constitutional symptoms, urinary tract symptoms, or fever. He denied any history of abdominal trauma as well. His family history was negative for malignancy and familial adenomatous polyposis (FAP). Upon physical examination, he was found to have a palpable mass over the right iliac fossa, relatively mobile and nontender. The rest of the examinations were unremarkable. The analyzed blood parameters were within normal range as well.

Colonoscopy findings were normal, with no intraluminal lesion seen. Following that, a CT scan of the abdomen and pelvis was ordered, showing a well-defined intraperitoneal mass over the right lumbar region. Tiny calcification foci were seen within the tumor, with no fat component. It caused mass effects to the adjacent ascending colon, with poor plane seen between ([Fig. 1]).

Fig. 1 Contrast-enhanced CT scan of the abdomen with (A) coronal, (B) axial, and (C) sagittal views. Well-defined, homogenously enhancing, intraperitoneal mass with soft tissue density seen at right lumbar measuring 6.5 × 8.1 × 7.7 cm (Anteroposterior x Width x Craniocaudal).

The intraoperative findings of a large globular mass arising from the ascending colon and adhering to the terminal ileum ([Fig. 2A,B]) with well-defined borders and smooth surfaces. There were no enlarged mesenteric lymph nodes with the initial impression of a gastrointestinal tumor (GIST). Hence, a limited right hemicolectomy was performed.

Fig. 2 Right hemicolectomy specimen. (A) Anterior & (B) posterior views. The large tumor arising anteriorly to the caecum adhered to the terminal ileum.

Upon gross histopathological examination, the mass measured 80 × 70 × 70 mm, with a glistening serosa surface. The cut section shows a homogenous whitish lesion, with a whorl pattern and an infiltrative border. No hemorrhage or necrosis was seen. Microscopically, the tumor tissues are composed of proliferating spindle-shaped cells arranged predominantly in long sweeping patterns ([Fig. 3A]), which is one of the essential diagnostic criteria. The tumor cells show elongated to spindle shaped nuclei, inconspicuous nucleoli, with indistinct pale eosinophilic cytoplasm ([Fig. 3B]). Both proximal and distal margins are free from tumor. Immunohistochemical smooth muscle actin (SMA) staining shows myofibroblastic differentiation ([Fig. 3C]) complemented with masson trichrome special stain showing a keloidal-type collagen stroma ([Fig. 3D]).

Fig. 3 Hematoxylin and eosin (H&E) and immunohistochemistry stain of the tumor. (A) Proliferation of spindle shaped cells arranged predominantly in a long sweeping pattern (essential diagnostic criteria), with scattered thin-walled blood vessels and densely eosinophilic keloidal-type collagen stroma at the right lower end (H&E, X40 magnification). (B) Elongated to spindle-shaped nuclei, with inconspicuous nucleoli and indistinct eosinophilic cytoplasm without substantial cytological atypia (H&E, X200 magnification). (C) SMA immunostaining shows membranous positivity resembling tram-track, indicating myofibroblastic differentiation. (D) Masson trichrome special stain shows keloidal-type collagen stroma.

He had an uneventful postoperative recovery and remained well at the 1-year follow-up.

 

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Discussion

Sporadic intraabdominal desmoid tumor is a rare entity. Although benign, it has high propensity for infiltrative growth, causing mass effect to surrounding organs.[1] For intraabdominal desmoid tumors, the most common site is at the small bowel mesentery.[4] These tumors are found to be associated with FAP, Gardner's syndrome, trauma, hormonal imbalance and prior surgery.[2] In the study by Peng et al., nearly a third of the patients had history of surgical procedure at site of the desmoid tumor, citing their correlation with surgical scars.[5] This tumor is notorious for its high recurrence rate postintervention (radiotherapy, surgery, medical therapy). In a large study of 426 patients with sporadic desmoid tumors, 75% of them were in complete remission after initial management, but nearly 50% relapsed.[6]

The differential diagnoses for solid abdominal tumors are extensive, and include gastrointestinal stromal (GISTs), colon adenocarcinoma, mesenteric lymphoma, carcinoid, desmoid, and liposarcoma.[4] The typical appearance of intraabdominal desmoid tumors on CT is that of a well-circumscribed solid soft tissue mass without calcifications.[1] However, GISTs of the small intestine or colon have similar CT scan findings, making them hard to differentiate radiologically.[7] Therefore, complete surgical resection would be next to ideal.

Desmoid fibromatosis usually shows membranous positivity with SMA immunostain resembling tram-track indicating of myofibroblastic differentiation. The desirable diagnostic criteria of nuclear expression with β-catenin immunostaining are not available in our center. Immunochemical staining is important to differentiate between GIST and desmoid tumors. The presence of GIST has been ruled out by negative expressions of both CD117 (c-kit) and DOG1 (sensitive and specific marker showing strong and diffuse expression), and supported by negative immunostaining of CD34, S-100, and caldesmon.

Surgical excision with clear margin remains the primary treatment option for symptomatic intraabdominal desmoid tumors. These tumors have a high tendency to recur following surgery, warranting surveillance.[5] Factors associated with local recurrence were the patient's age and tumor sites.[5] Margin-free resection (R0) is perhaps the most widely studied factor in the treatment of desmoid tumors. However, the results were controversial. A multivariate analysis stated that only age, tumor size, and tumor site were independent prognostic factors of recurrence.[7] Others described microscopically positive margins (R1) were associated with a higher local recurrence rate.[5] An R0 resection is ideal but the treatment should be individualized with calculated risk and benefit, based on the tumor proximity to vital organs, local complications, and morbidity associated with radical surgery.[8]

Proposed alternatives for desmoid tumors were radio- (RT), chemo-, and medical therapy, all of which showed promising results. One study showed that the event-free survival rates of patients with R0 resections and those treated nonsurgically were similar.[6] Among these methods, RT has shown to be beneficial in the treatment of desmoid tumors whether as adjuvant or mainstay therapy. It reduces the risk of local recurrence and provides good regional control of the disease.[9] The RT dose and technique vary depending on tumor site. A study comparing the local recurrences between surgery or RT alone and surgery with RT over a median period of 6 years found that the combined method resulted in significantly better local control (78%) compared with RT alone (75%) and surgery alone (61%). This finding is consistent with another paper analyzing long-term outcomes of desmoid tumor patients treated with RT.[9]

Traditional systemic cytotoxic chemotherapy may be the treatment of choice for unresectable desmoid tumor. Cytotoxic agents advocated for these tumors include methotrexate and vinblastine which show reasonable activity with tolerable toxicity in pediatric populations.[9] Medical therapy has also been proven to be effective in managing these tumors, with antihormonal therapy forming its main bulk. Desmoid tumors were observed to regress spontaneously after menopause and peak in incidence during and after pregnancy.

These observations form the basis of antihormonal therapy, in which tamoxifen is the most prescribed agent.[10] However, most studies on the efficacy of these drugs are of small sample sizes and case reports. Further research is needed to reach a conclusion regarding the effectiveness of tamoxifen against desmoids.[9] The use of nonsteroidal antiinflammatory drugs (NSAIDs) such as sulindac in the treatment of desmoid tumors is associated with partial and complete responses in several nonrandomized retrospective studies, either alone or in combination with hormonal agents such as tamoxifen. The overall response rate of patients treated with sulindac is about 50%, the majority of whom experienced a delayed response with a mean time of 24 months.[9] However, efficacy has not been proven through a randomized comparison.[10]

A wait-and-see policy has also been proposed for patients with good prognostic factors (> 37-years-old, tumor size < 7 cm, and located in the abdominal wall or intra-abdominally) as these tumors have an indolent course.[6] A similar strategy has also been advocated in another paper for primary desmoid tumors, which is confirmed by histopathology and located at a site that would not cause significant morbidity in case of tumor progression.[9]

 

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Conclusion

Sporadic intraabdominal desmoid tumor is a rare encounter which mimics that of malignant colon and GIST.

 

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Conflict of Interests

The authors have no conflict of interests to declare.

Authors' Contributions

XZ Ong - Conceptualization, data curation, software, writing – original draft; Anania MZ - Formal analysis, resources, validation; Zaidi Zakaria - Supervision, validation, writing – review and editing; Maya MY - Validation, investigation, writing – review and editing; Michael WPK - Project administration, resources, writing – review and editing.

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Publication History

Received: 30 May 2024

Accepted: 21 March 2025

Article published online:
25 July 2025