Squamous Carcinoma of the Colon and Rectum

Definition

• Squamous carcinoma arising in the colon and rectum

Covered separately

• Anal squamous cell carcinoma
• Colorectal adenosquamous carcinoma

Diagnostic Criteria

• Usual appearance of squamous carcinoma
• Lacks the frequent variety of patterns of anal squamous carcinoma
• Must not involve anal squamous mucosa
• Some require location >5 cm above dentate line
• Anal squamous carcinomas frequently extend into the rectum
• Must not be associated with a fistula
• Must not form any glands
• Mixed cases should be designated adenosquamous carcinoma
• Must not have history of squamous carcinoma elsewhere
• May be associated with inflammatory intestinal disorders
• Ulcerative colitis
• Schistosomiasis
• Amebiasis
• Prior radiation

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates : 1/31/10, 11/12/11

Supplemental studies

Immunohistology

• Staining for p16 is a useful surrogate for the presence of high risk HPV
  • Positive in 3 of 3 cases of rectal SCC in a recent study (Kong 2006)
    • Positive reaction requires strong, band-like staining
    • Both nucleus and cytoplasm usually stained
• Phenotype differs from anal squamous carcinoma and rectal adenocarcinoma:

	CAM5.4	AE1&3	HMW keratin 34BE12	CK7	CK20
Rectal SCC	80%	100%	100%	20%	0%
Anal SCC	0%	100%	100%	Focal	0%
Rectal Adenoca	100%	100%	Rare cells	Focal	100%

Nahas 2007

Genetic Analysis

• High risk human papilloma virus (HPV) demonstrated in 3 of 3 cases in a recent study (Kong 2006)

Differential Diagnosis

• Metastatic squamous carcinoma from other sites must be ruled out clinically

Clinical

• Historically poor prognosis with surgical treatment
• Therapy similar to anal squamous carcinoma
  • Therapy centered on radiation and chemotherapy followed by local excision, if there is a residual lesion, appears to give good results
  • One recent series of rectal SCC with 100% survival (Nahas 2007)

Grading / Staging

Grading

• There is no accepted grading scheme

Staging

• Colorectal TNM applies to all kinds of carcinoma
  • Some use TNM staging for anal squamous carcinoma instead

Bibliography

• Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
• Kong CS, Welton ML, Longacre TA. Role of human papilloma virus in squamous cell metaplasia-dysplasia-carcinoma of the rectum. Am J Surg Pathol. 2007 Jun;31(6):919-25.
• Nahas CS, Shia J, Joseph R, Schrag D, Minsky BD, Weiser MR, Guillem JG, Paty PB, Klimstra DS, Tang LH, Wong WD, Temple LK. Squamous-cell carcinoma of the rectum: a rare but curable tumor. Dis Colon Rectum. 2007 Sep;50(9):1393-400.
• Frizelle FA, Hobday KS, Batts KP, Nelson H. Adenosquamous and squamous carcinoma of the colon and upper rectum: a clinical and histopathologic study. Dis Colon Rectum. 2001 Mar;44(3):341-6.