Benign Abdominal Wall Tumors

Tumors of the abdominal wall exist in abundance and are a common consult that general surgery receives.

Table of Contents

Typical lipoma
- Most common lipoma
- Benign tumor of adipose tissue with thin fibrous capsule
- Presentation
  - Localized, encapsulated mass
  - Occurs throughout the body, varies in size
  - Majority occur in subcutaneous tissue, but can occur between muscle layers and within tendinous sheaths
  - Usually painless, but can have mass effect with compressing symptoms
- Diagnosis is clinical
- Treatment
  - Asymptomatic → observation
  - Symptomatic, concern for malignancy, patient preference/cosmesis → excision
Spindle cell lipoma
- Elongated spindle-shaped cells
- CD34+
Fibromyolipoma
- Stellate dendritic processes in myxoid stroma with fibrotic spindle-shaped bundles and adipocytes
Hibernoma (pseudolipoma)
- Abnormal growth of residual brown fat
- Brown fat is more common in infants → thighs, upper back, neck, arms
- Associated with 11q13 rearrangement → MEN1, AIP
Chondrolipoma
- Mature adipocytes, adipoblasts, and mucus-transparent cartilage-like matrices
- Predilection for adipose tissue and skeletal muscle
Angiolipoma
- Vascular tissue and mature adipocytes
- Can present with pain from the tumor which is usually due to thrombosis of the vascular structure → infarction and necrosis
Extremedullary myelipoma
- Trilinear myelogenous cell development characteristic of bone marrow
Familial multiple lipomatosis
- Rare autosomal dominant
- Multiple lipomas starting around age 30 and peaking at age 50

Can be associated with neurofibromatosis
Pathophysiology: benign nerve sheath tumors
Presentation
- Diameter <2 cm
- Numerous lesions → sporadic, solitary lesions
- Raised, soft, skin-colored nodule <2 cm in size
- Button-hole sign → lesion retracts into skin when direct pressure is applied
Diagnosis is clinical but may require biopsy
Treatment
- Asymptomatic → observation
- Symptomatic or concern for malignancy → excision

AKA neurilemmoma
Pathophysiology: pathologic growths of Schwann cells in neurologic sheath
Presentation
- Usually occur in head and neck
- Circumscribed swelling
- Can create pain and discomfort if associated with swelling
Histology
- Streaks of spindle-shaped cells and myxoid material
- S100+
Treatment: resection is curative

Rare myxoid tumor of skin and subcutaneous tissue
Presentation
- May arise in individuals with Carney syndrome
- Usually arise sporadically
- Pedunculated skin-colored lesion
Workup: no need for imaging or biopsy
Treatment
- Asymptotic → observation
- Symptomatic → surgical resection

Pathophysiology
- Benign fibrous histiocytomas or common fibrous histiocytoma
- Arise from dermis
Presentation
- Adults
- Firm solitary lesion
- Nontender, hyperpigmented, subcutaneous nodule
- Usually <1 cm and asymptomatic
Diagnosis is clinical and may require biopsy if uncertain
Treatment
- Asymptomatic → observation
- Symptomatic, concern for malignancy, patient preference/cosmesis → excision

Pathophysiology: arise from processes that differentiate the ductal and secretory cells of eccrine sweat glands
Presentation
- Size 3 mm – 5 cm
- Painful
- Raised lesion blue, pink, or purple in color
Histology
- Components of sweat glands
- S100+
Treatment: surgical resection (due to concern for malignancy)

Primarily composed of myofibroblasts, benign without metastasis
Locally aggressive with high local recurrence
Pathophysiology
- Arise from myofibroblasts
- Arise spontaneously
Presentation
- Can be locally aggressive
- Associated with high recurrence rate
- Anterior abdominal wall
  - Most common location
  - Often occur during or after pregnancy, trauma, or surgery
  - Deep seated, painless nonmobile mass often in fascial plane
- Intra-abdominal desmoid
  - Associated with Gardner’s syndrome and retroperitoneal fibrosis
  - Often encases bowel (difficult to perform resection)
Diagnosis
- CT: depends on composition
  - Can be homogenous or heterogenous
  - Can be hypointense or hyperintense
- Core needle biopsy: spindle cells, dense fibrosis, high cellularity, low mitotic index
Treatment
- Asymptomatic or stable size → observation can be observed
- Symptomatic → surgical resection
- Unresectable
  - Neoadjuvant radiation can be considered in complex cases
  - Chemotherapy (e.g., sulindac, tamoxifen)
  - Imaging may be needed to evaluate relationship to abdominal wall
- Consider colonoscopy to evaluate for familial adenosis polyposis

Collection of purulent fluid in dermis and subcutaneous tissue
Etiology: bacteria → Staphylococcus (most common), Streptococcus, majority are polymicrobial
Presentation
- Painful, fluctuant on exam
- Erythematous nodule
- May have surrounding cellulitis with associated induration
Diagnosis
- Physical exam
- Ultrasound or CT if uncertain of diagnosis
Treatment:
- Primary → surgical I&D
- Indications for antibiotics
  - Size ≥2 cm
  - Multiple lesions
  - Extensive surrounding cellulitis
  - Sepsis/systemic toxicity (fever, tachycardia, hypotension)
  - Immunosuppressed (diabetes(
  - Prosthetic devices
  - High risk for endocarditis
  - Failure of I&D

Pork tapeworm
Etiology
- Taenia solium (most common)
- Ingestion of larvae shed by parent worm into feces
Presentation
- Cyst formation throughout the body
- Cysts in subcutaneous tissue
Diagnosis
- Imaging
- Serology
- Cyst aspiration
- Cytology
Treatment: medical management

Echinococcal cyst
Etiology
- Echinococcus granulosus
- Usually cycles between canines and farm animals
Presentation
- Involves liver and lungs
- Slowly expanding mass with chronic discomfort
Treatment
- Albendazole
- Mass observation for resolution

Sebaceous cyst
Pathophysiology
- Benign subepidermal nodules
- Filled with keratin due to plugging of follicular orifice
Presentation
- Most common cutaneous cyst
- Sporadic
- Found anywhere on body
- Ranges in size from 0.5 cm – 2 cm
- Central punctum present
- Usually asymptomatic
Treatment
- Acute infection → incision and drainage
- After resolution of infection → curative excision

Mission