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Colon tumor

Carcinoma

Medullary carcinoma

Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 22 October 2011, last major update September 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features
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● Also called undifferentiated carcinoma; a subtype of poorly differentiated adenocarcinoma
● <1% of colorectal neoplasms
● Often elderly women, right sided tumors
● Strongly associated with high degree of microsatellite instability (MSI), indicative of loss of normal DNA repair gene function
● Often better clinical outcome independent of stage than microsatellite stable tumors or tumors with low levels of microsatellite instability; usually no/few nodal metastases
● May be more sensitive to 5 FU chemotherapy
● May have more metachronous colonic carcinomas

Case reports
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● 79 year old woman with ulcerated cecal tumor (Arch Pathol Lab Med 2005;129:113)

Gross description
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● Large with invasion into adjacent organs

Micro description
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● Expansive growth pattern of well circumscribed sheets of tumor cells
● Also nested, organoid or trabecular patterns, but no/minimal mucin production and no tubule formation
● Pushing border with prominent lymphocytic infiltration
● Cells are uniform, polygonal to round, small to medium sized with variable eosinophilic cytoplasm and small/medium nuclei with open chromatin and prominent nucleoli, frequent mitotic activity
● Neuroendocrine features but negative for neuroendocrine markers

Micro images
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Figure 1-tar black tumor with ulceration, 2-sheets of tumor cells with extensive necrosis, 3-cells have prominent nucleoli, 4-CK+


Loss of MSH2 expression; Medullary carcinoma (fig A) compared to poorly differentiated colon carcinoma (fig B)


Comparison of calretinin, CDX2 and MLH1 staining in medullary and poorly differentiated colon adenocarcinoma

Breast:

High grade tumor cells in syncytial pattern


MUC staining of medullary colon carcinoma

Positive stains
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● Keratin, CEA, EMA, Calretinin and CDX-2

Negative stains
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● Neuroendocrine markers, MLH1 and MSH2 (Mod Pathol 2002;15:741), p53

Flow cytometry
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● Diploid

Differential diagnosis
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● Lymphoepithelioma-like carcinoma

Additional references
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● Am J Clin Pathol 2005;123:56, Hum Pathol 1999;30:843, Int J Oncol 2010;37:901, Hum Pathol 2009;40:398

End of Colon tumor > Carcinoma > Medullary carcinoma

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