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Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Medullary carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumormedullary.html. Accessed July 14th, 2017.
Definition / general
- WHO recognized subtype of colon carcinoma with solid growth pattern (Hum Pathol 1999;30:843)
- Relatively rare; usually quoted as < 1% of colorectal neoplasms (Int J Oncol 2010;37:901)
Essential features
- 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
Terminology
- Older names: undifferentiated carcinoma, solid type poorly differentiated carcinoma, large cell minimally differentiated carcinoma
Epidemiology
- Often elderly women (average age ~70 years)
Sites
- Usually right sided
Case reports
- 79 year old woman with black, ulcerated cecal tumor (Arch Pathol Lab Med 2005;129:113)
Treatment
- Surgery and chemotherapy (although 5-FU not effective, as with other MSI high tumors)
Gross description
- Large, ulcerating colon mass
Gross images
Images hosted on other servers:
Fleshy, ulcerated lesion
Microscopic (histologic) description
- Malignant, well circumscribed neoplasm with solid growth pattern (no gland formation) and pushing border
- Can form nested, organoid or trabecular patterns
- Cells are uniform, polygonal to round, and medium sized with amphophilic cytoplasm, vesicular nuclei with prominent nucleoli and frequent mitotic activity
- Mucin production absent or very focal
- Prominent lymphocytic infiltration within and around tumor
Microscopic (histologic) images
Images hosted on other servers:
CK20+
Solid growth pattern
Medullary (A)
MLH1-, CDX2-
Breast:
tumor cells,
syncytial pattern
MUC1, TFF3
Positive stains
Negative stains
- MLH1 and MSH2 (Mod Pathol 2002;15:741); neuroendocrine markers
- CDX2 (positive in 19%), CK7 (positive in 13%), CK20 (positive in 44%) (Hum Pathol 2009;40:398)
Molecular / cytogenetics description
- Associated with microsatellite instability; therefore may be sporadic or arise in Lynch syndrome
- BRAF mutations common (Ann Surg Oncol 2015;22:2988)
- Kras mutations uncommon (Am J Pathol 2001;159:2239)
Differential diagnosis
- Lymphoepithelioma-like carcinoma: very rare in colon; EBER+
- Neuroendocrine carcinoma: positive for neuroendocrine markers (Am J Clin Pathol 2005;123:56)
Additional references
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