Invasive micropapillary carcinoma of the sigmoid colon: distinct morphology and aggressive behavior

Abstract

We report a case of invasive micropapillary carcinoma of the sigmoid colon in a 72-year-old female with anemia and abdominal pain. Grossly, the tumor demonstrated a deeply invasive, ulcerated fungating mass. Microscopically, the carcinoma was predominantly composed of micropapillae with reversed cell polarity, abundant neutrophils, and surrounded by clear spaces. Multifocal lymphovascular invasion was present with extensive lymph node metastasis. Immunohistochemically, the carcinoma cells were positive for CDX2, CK20 and monoclonal carcinoembryonic antigen. They were negative for CK7. The stroma-facing surface of the micropapillae was positive for CD10 and villin, confirming the inside-out growth pattern characteristic of micropapillary carcinoma. Work-up for distance metastasis was negative. The patient was alive and well 1.5 years after sigmoidectomy and postoperative chemotherapy.

Keywords: Adenocarcinoma; colon; invasive; metastasis; micropapillary.

Figure 1

The neoplastic cells form micropapillae with reserved polarity without central fibrovascular core. A. Low magnification showing micropapillae, singly or in small groups, surrounded by lacular-like clear spaces (H&E, ×200). B. High magnification showing reserved polarity with smooth terminal bar-like surface of the microvilli facing the lacunar-like spaces (H&E, ×400).

Figure 2

Collections of neutrophils infiltrating the micropapillae and occasionally spilling into the lacunar-like spaces, mimicking microabscess (H&E, ×400). Overt “dirty necrosis” is not seen.

Figure 3

Metastatic carcinoma with micropapillae (A, H&E, ×200) and psammoma bodies (B, H&E, ×400) in a lymph node.

Figure 4

Reversed polarity of the micropapillae demonstrated by immunostaining for villin (A) and CD10 (B) (original magnification × 100).

Figure 5

Negative CD31 mmunostaining of the lacunar-like spaces with tumor micropapillae (A, ×400) but positive immunostaining of the lymphovascular channels with metastatic tumor (B, ×400).

Figure 6

Positive nuclear staining of the tumor cells for MLH1 (A) and MSH2 (B) (original magnification, ×400)