Special Surgery 17. Anorectal Tumors: Symptoms, Diagnosis, Treatment

I. Rectal Cancer

Definition and Histology

• Malignant tumor arising from epithelial lining of rectum
• Mostly adenocarcinoma
• Rectum: distal large bowel, clinically staged and treated differently from colon because of pelvis, mesorectum and sphincter preservation issues
• Key operation principle: total mesorectal excision (TME)

Etiology and Risk Factors

• Adenoma-carcinoma sequence
• Diet low in fiber and high in red/processed/fatty meat
• Alcohol
• Smoking
• Obesity and type 2 diabetes mellitus
• Inflammatory bowel disease:

• Ulcerative colitis
• Crohn colitis

• Hereditary syndromes:

• FAP: APC tumor suppressor gene mutation
• Lynch syndrome / HNPCC: mismatch repair gene defect → microsatellite instability

Clinical Features

• Rectal bleeding, bright red or mixed with stool
• Change in bowel habits:

• Constipation
• Diarrhea
• Alternating pattern
• Narrow stools

• Tenesmus / feeling of incomplete evacuation
• Mucus discharge
• Painful defecation, especially low rectal/anal canal involvement
• Iron-deficiency anemia from chronic bleeding
• Pelvic pain, urinary symptoms or fistula symptoms in locally advanced disease
• Palpable rectal mass on DRE if low/mid rectum
• Weight loss and anorexia in advanced disease

Diagnosis

Clinical Examination

• History: bleeding, bowel habit change, pain, tenesmus, weight loss, family history
• Abdominal exam: mass, hepatomegaly, ascites
• Digital rectal examination:

• Detect low rectal mass
• Assess distance from anal verge
• Mobility/fixation
• Sphincter tone and possible sphincter involvement

Endoscopy and Biopsy

• Colonoscopy + biopsy = gold standard
• Confirms histology
• Examines whole colon for synchronous cancers/polyps
• Rigid proctoscopy/flexible sigmoidoscopy useful to measure exact tumor height from anal verge
• CT colonography can be used if colonoscopy incomplete, but cannot biopsy

Laboratory

• CBC: anemia, decreased Hb/Hct
• Liver/renal function before treatment
• CEA:

• Baseline before treatment
• Useful for follow-up/recurrence monitoring
• Not diagnostic

Staging

• MRI pelvis:

• Best local staging test for rectal cancer
• Assesses T stage, nodal disease, mesorectal fascia/circumferential resection margin
• Assesses extramural vascular invasion, sphincter/levator involvement and relation to peritoneal reflection

• Endorectal ultrasound / EUS:

• Useful for early T1/T2 lesions and local excision planning
• Less useful for bulky/stenosing advanced tumors

• CT chest/abdomen/pelvis:

• Distant metastases: liver, lung, peritoneum, nodes

• PET-CT only selected cases, not routine replacement for CT/MRI

TNM Staging: Rectal Adenocarcinoma

T Stage

• Tis: carcinoma in situ / lamina propria, no submucosal invasion
• T1: submucosa
• T2: muscularis propria
• T3: through muscularis propria into perirectal/mesorectal tissue
• T4a: penetrates visceral peritoneum
• T4b: invades adjacent organs/structures

N and M Stage

• N0: no regional lymph node metastasis
• N1: 1-3 regional lymph nodes or tumor deposits depending on subclassification
• N2: 4 or more regional lymph nodes
• M0: no distant metastasis
• M1: distant metastasis

Stage Groups

• Stage 0: Tis
• Stage I: T1-2 N0
• Stage II: T3-4 N0
• Stage III: any N+
• Stage IV: M1

II. Rectal Cancer Treatment

Treatment by Stage

Stage 0-I / Early Rectal Cancer

• Surgical resection is main treatment
• Local excision can be considered for carefully selected early tumors:

• Small, usually <3 cm
• T1, favorable histology
• No lymphovascular invasion
• Well/moderately differentiated
• Mobile, accessible lesion
• No suspicious nodes

• High-risk T1 or T2 lesions usually require radical resection because nodal risk is relevant

Stage II-III / Locally Advanced Rectal Cancer

• Classical approach: neoadjuvant chemoradiotherapy → TME surgery → adjuvant chemotherapy depending on pathology/protocol
• Total neoadjuvant therapy is increasingly used:

• All or most chemotherapy and radiotherapy before surgery
• Improves systemic treatment delivery
• Can increase complete response rate

• Short-course radiotherapy or long-course chemoradiotherapy chosen by MDT based on tumor risk and protocol
• Selected complete clinical responders may enter watch-and-wait / nonoperative management with intensive surveillance

Stage IV

• Systemic therapy is main treatment
• Resectable liver/lung metastases: combined curative-intent strategy may be possible
• Palliative surgery/intervention if:

• Obstruction
• Perforation
• Uncontrolled bleeding
• Severe symptoms from primary tumor

• Options: diverting stoma, stent in selected upper rectal/rectosigmoid obstruction, resection in selected cases, radiotherapy for bleeding/pain

Surgical Approaches

Local Excision / Transanal Excision

• For selected early low rectal tumors
• Techniques:

• Transanal excision
• TEM = transanal endoscopic microsurgery
• TAMIS = transanal minimally invasive surgery

• Requires strict pathology review; unfavorable features → radical surgery

Anterior Resection / Low Anterior Resection: Dixon Operation

• Removal of diseased rectum with TME or tumor-specific mesorectal excision depending on height
• Colorectal or coloanal anastomosis
• Used for upper and middle rectal cancers, and selected low rectal cancers when sphincter can be preserved
• High anterior resection: anastomosis above peritoneal reflection
• Low anterior resection: anastomosis below peritoneal reflection
• Temporary diverting ileostomy often used for low anastomosis
• Possible complication: low anterior resection syndrome with urgency, frequency, incontinence/fragmentation

Abdominoperineal Resection: Miles Operation

• Removal of rectum, anal canal and sphincter complex
• Permanent end colostomy
• Indication:

• Very low rectal cancer involving sphincters/levator
• Cannot obtain safe distal/circumferential margin with sphincter preservation
• Poor baseline sphincter function in selected cases

Hartmann Procedure

• Rectosigmoid/rectal resection with end colostomy and closed rectal stump
• Mainly emergency or high-risk setting:

• Obstruction
• Perforation
• Unstable patient
• Unsafe anastomosis

Follow-Up After Rectal Cancer Treatment

• CEA monitoring if initially elevated/useful
• Colonoscopy:

• Detect metachronous cancer/polyps
• Assess anastomosis/local recurrence when relevant

• CT chest/abdomen/pelvis for metastasis surveillance according to stage/protocol
• Pelvic MRI/endoscopy/DRE in patients at high local recurrence risk or watch-and-wait protocol
• Assess bowel, urinary, sexual function and stoma issues

III. Anal Cancer

Definition and Histology

• Malignant tumor of anal canal or anal margin
• Most common: squamous cell carcinoma
• Anal canal SCC is biologically and therapeutically different from rectal adenocarcinoma
• Main goal: cure while preserving sphincter function

Risk Factors

• HPV infection, especially types 16 and 18
• History of anal warts / condyloma
• Immunosuppression:

• HIV
• Transplant immunosuppression

• Smoking
• Receptive anal intercourse
• Multiple sexual partners
• Prior cervical/vulvar/vaginal HPV-related neoplasia

Clinical Features

• Rectal/anal bleeding
• Anal pain
• Perianal mass or ulcer
• Pruritus
• Discharge
• Tenesmus
• Palpable anal canal mass on DRE
• Inguinal lymphadenopathy
• Can be misdiagnosed as hemorrhoids

Diagnosis and Staging

• Inspection of perianal skin
• DRE
• Anoscopy/proctoscopy + biopsy = diagnostic confirmation
• Palpate inguinal nodes
• HIV testing and HPV-related disease assessment when appropriate
• Local staging:

• MRI pelvis
• Endoanal ultrasound for selected small/local lesions

• Distant/nodal staging:

• CT chest/abdomen/pelvis
• PET-CT often useful for nodal/distant staging and radiotherapy planning

Treatment

Non-Metastatic Anal Canal SCC

• Definitive chemoradiotherapy is first-line for most patients
• Nigro-type protocol:

• Radiotherapy
• 5-FU or capecitabine
• Mitomycin C

• High cure rate and sphincter preservation in many patients
• Response can continue for months after chemoradiotherapy; avoid premature salvage surgery unless progression is clear

Surgery

• Wide local excision:

• Selected small anal margin/perianal skin SCC
• No sphincter involvement
• Adequate margins possible

• Abdominoperineal resection:

• Reserved for persistent or recurrent anal canal cancer after chemoradiotherapy
• Permanent colostomy

Metastatic Anal Cancer

• Systemic chemotherapy / immunotherapy depending on line, biomarkers and protocol
• Palliative radiotherapy for pain, bleeding or local symptoms
• Stoma or local intervention if obstruction/fistula/sepsis

IV. Benign Anorectal Tumors and Key Differentials

Rectal Adenomas and Polyps

• May be asymptomatic
• Symptoms:

• Minor bleeding
• Mucus
• Tenesmus if low rectal
• Prolapse if pedunculated distal lesion

• Diagnosis: DRE/proctoscopy/colonoscopy + histology
• Treatment:

• Endoscopic polypectomy
• EMR/ESD for larger sessile lesions
• Transanal excision/TEM/TAMIS for selected rectal adenomas not removable colonoscopically
• Radical resection if invasive cancer or high-risk malignant polyp features

Anal Condyloma and Buschke-Lowenstein Tumor

• HPV-related warty lesions
• Can be multiple/extensive
• Giant condyloma = Buschke-Lowenstein tumor:

• Locally destructive verrucous lesion
• Low metastatic risk but high recurrence/local invasion
• Can undergo malignant transformation

• Symptoms: perianal mass, discharge, bleeding, hygiene problems, pain
• Treatment:

• Topical agents for small condylomas: imiquimod, podophyllotoxin, trichloroacetic acid depending on setting
• Ablation/laser/electrocautery
• Surgical excision for large/extensive lesions
• Biopsy suspicious, ulcerated, indurated or recurrent lesions

Other Benign / Rare Anorectal Tumors

• Lipoma, leiomyoma, GIST, neuroendocrine tumor, melanoma and lymphoma can occur but are less common
• Anal melanoma is rare but aggressive; pigmented or amelanotic anal mass needs biopsy
• Differential diagnosis of bleeding/pain:

• Hemorrhoids
• Anal fissure
• Abscess/fistula
• IBD proctitis
• Solitary rectal ulcer syndrome

• Rule: persistent anorectal bleeding, pain, mass or ulcer needs proper examination and biopsy/endoscopy, not assumption of hemorrhoids