Micropapillary carcinoma (MC) has been recently recognized to be a rare but distinctive variant of adenocarcinoma in several anatomic sites, including breast, urinary bladder, lung, the major salivary glands, and the pancreas.1–6 MC is pathologically characterized by small neoplastic cell clusters surrounded by aberrant stromal spaces, and it is clinically associated with a poor patient prognosis and extensive lymph node metastasis.7 At present, there has been only a limited number of reports about colorectal MC.5 We present a case of MC of the ascending colon with distant metastasis.

Case Report

A 61-year-old female patient presented with abdominal pain for 1 month and was hospitalized in a regional hospital. Contrast enema radiography showed stenosis in the ascending colon (Fig. 1A). The colonoscopy revealed an ulcerative tumor in the same portion (Fig. 1B), and a biopsy revealed an adenocarcinoma. Subsequently, the patient was transferred to the Department of Surgery at the Teikyo University School of Medicine. The chest computed tomography scans showed multiple nodules in both lungs, suggesting the presence of lung metastases (Fig. 2). The patient's past medical and surgical histories were unremarkable. The patient therefore underwent a right hemicolectomy with a lymph node dissection. However, lung metastases were not surgically resected because multiple metastatic lesions were present. During surgery, a white peritoneal nodule was detected in the abdominal cavity, which was also resected. Pathologic examination revealed the ulcerative tumor, 3.3 × 3.0 cm in size, in the ascending colon (Fig. 3). The tumor invaded the serosa. The microscopic findings of the colon tumor revealed characteristics of both conventional tubular adenocarcinoma and MC (Fig. 4A). In MC, a tumor consisting of several neoplastic cells without a fibrovascular core was found to have proliferated into the stroma. Tumor clusters were surrounded by clear empty spaces (Fig. 4B). The microscopic findings of a peritoneal nodule showed a tubular adenocarcinoma (Fig. 5).

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Discussion

MC is observed in the mammary gland, the urinary tract, the lung, and the salivary glands, and the incidence of mammary MC has been reported to be 0.9% to7%.1,2 However, MC is rare in the colon and rectum. MC is associated with frequent lymphovascular invasion, lymph node metastases, distant metastases, and a higher tumor stage compared with other types of adenocarcinomas in the colon and rectum.7 Patients with MC have a poor prognosis because of the high incidence of metastasis.7 We performed a PubMed search using key words “micropapillary carcinoma” and “colon” or “colorectal” and found only 8 reported patients with colorectal MC (Table 1).8–13 As shown in Table 1, reported cases with MC show high malignancy and poor prognosis. In the present case, the patient presented with multiple lung metastases and peritoneal dissemination in spite of a small primary carcinoma of only 33 mm in size.

Table 1 Reported cases of micropapillary carcinoma of the colon

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MC is observed in the colorectum and also in the mammary gland, bladder, lung, and stomach.14 However, it has been reported that there is heterogeneity of micropapillary patterns depending on the site of the cancers.15 Ohtsuki et al15examined MCs in the breast, bladder and colon cancers by immunohistochemistry using antibodies to KL-6, epithelial membrane antigen (EMA), MUC1 (CD227), and CD 10 and showed that MCs of the colon were different in character from breast and urinary bladder cancer. The precise mechanism underlying these differences has not been fully clarified. They suggested that this heterogeneity of the micropapillary pattern in various cancers needs to be investigated with a larger number of cases in further study.

The optimal chemotherapy or adjuvant chemotherapy for the colorectal MCs has not yet been established. In the present case, we have been administering FOLFOX (+ bevacizumab) chemotherapy to treat lung metastasis of the patient for 15 months after surgery. The number and the size of lung metastases increased to a small extent; however, the patient is well without symptoms at the present time. Further study is expected to clarify which regimen of chemotherapy is optimal for the treatment of metastatic lesions from colorectal MCs.