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Colon tumor

Carcinoma

Adenocarcinoma of colon

Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 13 October 2011, last major update September 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features
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● 98% of colonic cancers are adenocarcinomas
● Rarely associated with endometriosis and unopposed estrogen therapy (Am J Surg Pathol 2000;24:513); these cases usually involve serosa and spare mucosa, have endometrioid histology and squamous differentiation; important to differentiate since staging and treatment may be different
● Only rarely produces pseudomyxoma peritonei, even if mucinous
● Right colon tumors: polypoid exophytic masses; anemia, weakness and fatigue are common, but obstruction is uncommon; iron deficiency anemia in older man is presumed to be a GI carcinoma unless proven otherwise
● Left sided tumors: annular, encircling lesions (napkin ring constrictions of bowel); diarrhea, obstructive symptoms
● Rectosigmoid tumors: usually more advanced at presentation

Prognostic factors
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●Poor prognostic factors: high grade, possibly intramural venous invasion (identify with elastic stain, J Clin Pathol 2002;55:17)

Case reports
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Metastases:
● Cervix in 17 year old girl (J Reprod Med 2005;50:793)
● Ear (Ear Nose Throat J 2005;84:36)
● Kidney (Int J Urol 2005;12:93)
● Larynx (Acta Otolaryngol 2006;126:661)
● Mandible (Head Neck 2005;27:729)
● Perianal fistula (Int Semin Surg Oncol 2006;3:25)
● Skin (Ann Acad Med Singapore 2006;35:585, Int Semin Surg Oncol 2006;3:2)
● Sphenoid sinus (Otolaryngol Pol 2005;59:429)
● Thyroid gland (Tumori 2006;92:252, Endocr J 2006;53:339)

Other:
● Co-existing GIST (Int J Colorectal Dis 2007;22:109)
● Co-existent mantle cell lymphoma (Arch Pathol Lab Med 2003;127:E64)
● With enteroliths (Actas Urol Esp 2006;30:206)
● With hypercalcemia (Surg Today 2005;35:692)
● Post urinary diversion for exstrophy (World J Surg Oncol 2004;2:20)

Gross description
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● Usually single
● Multiple tumors can be synchronous (two or more masses identified at the same time) or metachronous (a spatially separated mass identified over different time in a patient with a previous history of colon cancer; usually happens in association with inflammatory bowel disease or familial syndromes)
● Polypoid or ulcerative
● May have serosal puckering if muscularis propria involved

Gross images
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Napkin ring lesion


Invasion through muscularis propria


Exophytic tumor

Superficial tumor


Rectal tumor


Heaped up edges and central ulceration

       

Tattooed sigmoid colon

   

Ascending colon

Micro description
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● Well to poorly differentiated tumor cells with marked desmoplasia, particularly at edge of tumor, often mucin producing
● Glands often filled with necrotic debris (“dirty necrosis”)
● Inflammatory cells and scattered neuroendocrine cells common (Pol J Pathol 2005;56:89)
● Rarely germ cell elements (Arch Pathol Lab Med 2001;125:558)
● Low grade (grade 1): well differentiated, 15-20% of all carcinomas; well formed glands or simple tubules with uniform, basally oriented nuclei, resembles adenomatous epithelium
● Moderately differentiated (grade 2): 60-70% of all carcinomas; tubules may be simple, complex or slightly irregular; loss of nuclear polarity
● High grade (grade 3): poorly differentiated in 50% or more of tumor (i.e. less than 50% gland formation), 15-20% all of carcinomas; majority of tumor (excluding advancing edge of tumor) is sheets of cells without gland formation; usually right sided (Hepatogastroenterology 2004;51:1698)

● Note: pre-operative histologic grading is not accurate (J Med Assoc Thai 2005;88:1535)

Micro images
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Whole mount scan

   

Moderately differentiated tumor


Mucinous and undifferentiated areas


Glands filled with necrotic debris

Serosal involvement

       

Venous invasion


Colloid carcinoma-like area


Signet ring cells


Metastatic to lymph node


CEA, AFP, hCG stains


p53

Virtual slides
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Adenocarcinoma

Positive stains
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● CK20 (Arch Pathol Lab Med 2001;125:1074, Mod Pathol 2000;13:962), mucin (MUC1 and MUC3), CEA, B72.3 and CDX2 (sensitive but not that specific, Hum Pathol 2007;38:72, Am J Surg Pathol 2003;27:303)
● Also hCG (often), p53, P504S (Am J Surg Pathol 2002;26:926), CD10 (stromal cells, Hum Pathol 2002;33:806), estrogen receptor (Hum Pathol 2001;32:940 but see Am J Clin Pathol 2000;113:364), villin
● May have scattered endocrine cells

Negative stains
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● CK7 (CK7 can be expressed in rectal adenocarcinoma, and should not be used as the sole basis for excluding a rectal primary, Appl Immunohistochem Mol Morphol 2009;17:196), HepPar1, DPC4 (SMAD4), PR (Am J Clin Pathol 2000;113:364), MUC2 and MUC5AC

EM description
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● Prominent microfilaments perpendicular to cell membrane and entering the brush border

Additional references
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● Clin Cancer Res 2005;11:3766 (algorithm for adenocarcinoma of unknown primary-figure 1C), eMedicine

End of Colon tumor > Carcinoma > Adenocarcinoma of colon

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