Surgical Pathology Criteria

Undifferentiated Carcinoma of the Colon and Rectum

Differential Diagnosis

Colorectal Medullary Carcinoma Colorectal Undifferentiated Carcinoma NOS
Lacks any gland formation May have <5% gland formation
Uniform small to medium sized nuclei Pleomorphic large nuclei
Uniformly prominent nucleoli Variable nucleoli
Pushing border Infiltrative border
Prominent lymphoid infiltrate in virtually all cases Lymphoid infiltrate variable

Colorectal Undifferentiated Carcinoma NOS Colorectal Small Cell Neuroendocrine (Undifferentiated) Carcinoma
Chromogranin and synaptophysin at most focal or scattered Chromogranin or synaptophysin may be negative or positive
Vesicular nuclei Chromatin finely granular, stippled
Prominent nucleoli Inconspicuous nucleoli
Pleomorphic large cells Uniform small to medium size cells

Colorectal Undifferentiated Carcinoma NOS Colorectal Large Cell Neuroendocrine Carcinoma
Chromogranin and synaptophysin at most focal or scattered Chromogranin or synaptophysin must be positive in at least 20-50% of cells
Vesicular nuclei Chromatin finely granular, stippled
Prominent nucleoli Inconspicuous nucleoli
Does not form rosettes May form rosettes

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