13
Furuya 1
2011
81
M Hepatic flexure
Right hemicolec- tomy
PAS, D-PAS, CEA, AFP, EMA, CK AE1/3, CK20, CD117, B -catenin CK7, CD10, CK20, CDX2, CD15, NSE
Lymph node omentum, lung, liver
Died 12 months after diagnosis
14
Thelin
2011
25
M Hepatic flexure
Right hemicolec- tomy and
Lymph node & omentum
Died six months after diagnosis
chemo- therapy
for metastatic clear cell adenocarcinoma (Figure 4). This diagnosis prompted two therapeutic cycles of capecitabine (1,000 mg morning dosage and 500 mg dos- age, Monday through Friday) and oxaliplatin (85 mg/m 2 every three weeks), in conjunctionwith oncology follow-up. Unfortunately, postoperative and oncological follow-up periods were complicated by a small bowel obstruction, refractory to medical management. Several abdominal nodules were identified during surgery to lyse abdominal adhesions, which were later confirmed to be metastatic foci by histology. Given his dismal prognosis, the patient rejected additional chemotherapy and irradiation in favor of pallia- tive measures. He expired in hospice care six months after his initial diagnosis. No autopsy was performed. DISCUSSION Primary clear cell adenocarcinoma of the colon and rectum is rare. This is the 14th reported case, according to the results of the authors’ searches on PubMed (Table I), 1-13 and the youngest case ever reported. Previously, the average reported age at diagnosis was 56 years old. The ascending colon location is also unusual for primary clear cell adenocarcinomas, as 11 reported cases involve the left colon. 2-12 Thus, this patient’s specific tumor is not only rare in occurrence, but also in early age of onset and location. Clear cell adenocarcinomas usually occur in the kidney and within tissues of Müllerian system derivation, such as the lower urinary and female genital tracts; other less com- mon sites include the larynx, breast, pancreas, stomach, biliary system, and colon. 4,8-10 The histologic features of clear cell adenocarcinomas include rounded or polygonal-shaped cells withwell-defined cell membranes and large amounts of clear or granular cytoplasm, typically attributed to abundant cytoplasmic glycogen. 15,16 Morphologically, primary colonic clear cell adenocarcinoma shares traits with the aforemen- tioned and more common clear cell malignancies of the uterus, kidney, and ovaries. Given the tumoral presentation in a male, our differential included renal cell carcinoma, transitional cell carcinoma, and a clear cell adenocarcinoma of colonic or prostatic origin. The typical immunohistochemical profile for adeno- carcinomas arising within the colon is strong expression of CK20 without expression of CK7. The tumor in our case
showed an uncharacteristic staining pattern for a primary colonic tumor exhibiting strong staining with CK7 but only focal positivity with CK20. Similarly, one of the 13 reported cases in the rectosigmoid region also displayed diffuse strong positivity for CK7 without staining of CK20. 7,14 Morphologic similarities between the clear cell carcino- mas arising at diverse sites and the uncommon occurrence of clear cell adenocarcinoma within the colon make it difficult to differentiate this variant of colonic adenocarcinoma from a metastatic process. In our case, the patient underwent several full-body CT scans and a PET scan to rule out metastatic disease to the colon from another source. These studies failed to identify any alternative primary origin for the malignancy, specifically excluding the more common sites of renal and prostate origin. Prognosis is difficult to ascertain given the paucity of reported cases. Seven cases have unknown survival informa- tion. 2,3,6,7,9,10,12,13 Two cases report no reoccurrence at one-year follow-up without further information. 4 Outcomes from the remaining five cases, including ours, have a mean survival of 10.2 months from diagnosis, suggesting this variant to be an aggressive cancer. 4,5,8 Lymph node metastasis was re- ported in a total of five cases, including ours. Most patients underwent surgical therapy, even in advanced age. 8 Unfortunately, little is known about the incidence and prognosis of primary colonic clear cell adenocarcinoma given the paucity of reported cases. No screening genetic analysis tests are currently recommended for detection of primary clear cell adenocarcinoma, a rare entity. The authors stress the importance of screening colonoscopies in the early detection and intervention of colorectal cancers. While our patient was too young to fall within the targeted age group of 50 years or older, nine of the previously cited cases may have benefited from earlier identification and intervention. With the increased availability of the electronic medical record, advancements and accessibility of radiographic im- aging, and the growing spectrum of immunohistochemical stains, the identification of definitive cases of primary clear cell adenocarcinoma of the colon may increase. ACKNOWLEDGEMENTS Special thanks to Dr. JohnHutchings of the Department of Gastroenterology, Louisiana State University Health Sci-
J La State Med Soc VOL 166 July/August 2014 147
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