Atypical Presentation of Colon Adenocarcinoma: A Case Report
Atypical Presentation of Colon Adenocarcinoma: A Case Report
Adenocarcinoma of the colon in young adults in sub-Saharan Africa is a perceived rarity. However, increasing reports show that it occurs often. Rubin and colleagues reported a series of three young adults from Eastern Africa (two from Kenya and one from Ethiopia) who had peculiar presentations similar to those of our patient. The three lived in the US for a period of six to 18 years before disease presentation, and, as with our patient, two had a family history of colon cancer or inflammatory bowel disease. However, unlike our patient, who had none of the symptomatology of colon cancer, one of the patients presented with malena, and the others presented with frank rectal bleeding, abdominal pain, and nausea.
A study in Turkey revealed the occurrence of colorectal carcinoma in children younger than 18 years of age. These children all presented with advanced disease (Dukes stage C and D) and had peritoneal involvement while the predominant histopathological type was mucinous adenocarcinoma, as was the case in our patient.
Peritoneal carcinomatosis is estimated to occur in about one out of 10 individuals (10%) with colorectal carcinoma. Intraperitoneal spread in colorectal carcinoma results from full-thickness invasion of the bowel wall by an invasive tumor or as a result of the rupture of a structure by a non-invasive tumor, such as the mucus-producing cystadenocarcinoma of the appendix. In our patient, the former was more likely. Most colorectal carcinomas occur after malignant transformation of adenomatous polyps. Transformation involves inactivation of tumor suppressor genes (adenomatous polyposis coli, p53 genes), mutation of oncogenes and or growth regulators (K-ras), and mutations caused by dysfunction in the deoxyribonucleic acid (DNA) mismatch repair genes (MMR genes).
Colonoscopy and postmortem examination revealed that our patient had multiple polyps. This might explain why he developed adenocarcinoma of the colon. It is likely, given his young age and the presence of multiple colon polyps, that he had one of the polyposis coli syndromes. We did not undertake genetic studies to corroborate this.
Our patient presented with 'B' symptoms (fever, drenching sweats, and more than 10% weight loss) and ascites. The differential diagnosis for this presentation in our setting includes HIV/AIDS with its comorbidities, decompensated liver disease, abdominal tuberculosis, tumors of lymphoid origin, and peritoneal carcinomatosis. All of these were excluded after thorough investigations were done.
Several studies have shown that routine cytopathology using ascitic fluid smears is positive for malignant cells in two out of 10 patients with ascites. This is because, unless the ascitic fluid is cytospun, smears on slides will give false-negative results since the malignant cells are widely dispersed in the vast amounts of ascitic fluid. Often, clinicians submit only tiny amounts (5 to 10 mL) of fluid, which are not diagnostically useful.
Large amounts of ascitic fluid (at least 500 mL) should be sent to the pathology laboratories and cytospun so that the sediment is made into cell blocks. This is the best way of detecting malignancy since the malignant cells will sediment at the bottom and will be available after the rest of the fluid is decanted away to make it into a cell block. Cytopathology, if properly carried out, has a reported sensitivity of 60% and a specificity of 100%.
The histopathological types of colorectal carcinoma include adenocarcinoma, which is the most common type. Adenocarcinomas may be well-differentiated, often arising within a villous adenoma, or poorly-differentiated. The poorly-differentiated tumors (for example, signet ring cell carcinomas) have a poor prognosis and tend to affect younger patients. Most are well-differentiated adenocarcinomas and are classified according to mucin content. Mucin-secreting adenocarcinomas have less than 50% mucin production, mucinous carcinomas have more than 50% extracellular mucin, and signet ring carcinomas have intracellular mucin that displaces the nucleus to one side. Diagnosis of signet ring adenocarcinomas is made when at least 50% of the cells are of the signet ring type. Young people most commonly present with advanced disease and have defects in DNA MMR and microsatellite instability.
The other histological variants of colorectal carcinomas are squamous cell carcinoma, adenosquamous carcinoma, malignant carcinoid tumors, and embryonal rhabdomyosarcomas, the last of which are very rare. The rest are undifferentiated and medullary adenocarcinomas.
Discussion
Adenocarcinoma of the colon in young adults in sub-Saharan Africa is a perceived rarity. However, increasing reports show that it occurs often. Rubin and colleagues reported a series of three young adults from Eastern Africa (two from Kenya and one from Ethiopia) who had peculiar presentations similar to those of our patient. The three lived in the US for a period of six to 18 years before disease presentation, and, as with our patient, two had a family history of colon cancer or inflammatory bowel disease. However, unlike our patient, who had none of the symptomatology of colon cancer, one of the patients presented with malena, and the others presented with frank rectal bleeding, abdominal pain, and nausea.
A study in Turkey revealed the occurrence of colorectal carcinoma in children younger than 18 years of age. These children all presented with advanced disease (Dukes stage C and D) and had peritoneal involvement while the predominant histopathological type was mucinous adenocarcinoma, as was the case in our patient.
Peritoneal carcinomatosis is estimated to occur in about one out of 10 individuals (10%) with colorectal carcinoma. Intraperitoneal spread in colorectal carcinoma results from full-thickness invasion of the bowel wall by an invasive tumor or as a result of the rupture of a structure by a non-invasive tumor, such as the mucus-producing cystadenocarcinoma of the appendix. In our patient, the former was more likely. Most colorectal carcinomas occur after malignant transformation of adenomatous polyps. Transformation involves inactivation of tumor suppressor genes (adenomatous polyposis coli, p53 genes), mutation of oncogenes and or growth regulators (K-ras), and mutations caused by dysfunction in the deoxyribonucleic acid (DNA) mismatch repair genes (MMR genes).
Colonoscopy and postmortem examination revealed that our patient had multiple polyps. This might explain why he developed adenocarcinoma of the colon. It is likely, given his young age and the presence of multiple colon polyps, that he had one of the polyposis coli syndromes. We did not undertake genetic studies to corroborate this.
Our patient presented with 'B' symptoms (fever, drenching sweats, and more than 10% weight loss) and ascites. The differential diagnosis for this presentation in our setting includes HIV/AIDS with its comorbidities, decompensated liver disease, abdominal tuberculosis, tumors of lymphoid origin, and peritoneal carcinomatosis. All of these were excluded after thorough investigations were done.
Several studies have shown that routine cytopathology using ascitic fluid smears is positive for malignant cells in two out of 10 patients with ascites. This is because, unless the ascitic fluid is cytospun, smears on slides will give false-negative results since the malignant cells are widely dispersed in the vast amounts of ascitic fluid. Often, clinicians submit only tiny amounts (5 to 10 mL) of fluid, which are not diagnostically useful.
Large amounts of ascitic fluid (at least 500 mL) should be sent to the pathology laboratories and cytospun so that the sediment is made into cell blocks. This is the best way of detecting malignancy since the malignant cells will sediment at the bottom and will be available after the rest of the fluid is decanted away to make it into a cell block. Cytopathology, if properly carried out, has a reported sensitivity of 60% and a specificity of 100%.
The histopathological types of colorectal carcinoma include adenocarcinoma, which is the most common type. Adenocarcinomas may be well-differentiated, often arising within a villous adenoma, or poorly-differentiated. The poorly-differentiated tumors (for example, signet ring cell carcinomas) have a poor prognosis and tend to affect younger patients. Most are well-differentiated adenocarcinomas and are classified according to mucin content. Mucin-secreting adenocarcinomas have less than 50% mucin production, mucinous carcinomas have more than 50% extracellular mucin, and signet ring carcinomas have intracellular mucin that displaces the nucleus to one side. Diagnosis of signet ring adenocarcinomas is made when at least 50% of the cells are of the signet ring type. Young people most commonly present with advanced disease and have defects in DNA MMR and microsatellite instability.
The other histological variants of colorectal carcinomas are squamous cell carcinoma, adenosquamous carcinoma, malignant carcinoid tumors, and embryonal rhabdomyosarcomas, the last of which are very rare. The rest are undifferentiated and medullary adenocarcinomas.