Colorectal Nonadenocarcinoma in South Korea.

See Article on Page 390-397

Although most colorectal cancers are adenocarcinomas, there are several histological types of colorectal cancers, such as neuroendocrine tumors (NETs), lymphomas, gastrointestinal tumors (GISTs), melanomas, squamous cell carcinoma, and sarcomas, accounting for 2%–6% of all colorectal cancers [1, 2]. Using a nationwide, population-based cancer registry, the authors investigated the incidence and clinical characteristics for these rare colorectal cancers [2]. This analysis was performed to update the incidences of rare histological types of colorectal cancers in South Korea. I believe that this analysis can facilitate further investigations regarding more accurate prognosis and clinical impact in the future.

NETs originate from the diffuse system of neuroendocrine cells and constitute 2% of all gastrointestinal (GI) malignancies [3]. Although colonic NETs are rare, their incidence has been increasing from 0.002 per 100,000 individuals in 1973 to 0.2 per 100,000 individuals in 2004, according to a western registry [4]. Approximately 70% of colonic NETs occur in the right colon, especially in the cecum [5]. Moreover, the incidence of rectal NETs has been increased 10-fold over the last 30 years, which is approximately 1 per 100,000 individuals [6]. A previous Korean study showed that the mean age at diagnosis of rectal NETs was 50 years and rectal NETs were somewhat more common in males than in females [7]. Complete resection of NETs is generally recommended according to their size, but other treatment options are also available [3].

GISTs are the most common GI mesenchymal tumors and account for 0.1%–3.0% of all GI malignancies [8, 9]. The annual incidence of GISTs is estimated to be 1–2 per 100,000 individuals [10]. The median age at diagnosis of GISTs is 60 years, and GISTs do not have any sex or race predominance [11]. Surgical resection remains the gold standard management for GISTs, and imatinib is currently used in the neoadjuvant, adjuvant, and metastatic disease setting [12].

Despite the rare occurrence of various colorectal nonadenocarcinomas, surgical resection is considered important for the cure. Further studies are needed to better understand the progression and long-term oncological outcomes of these rare tumors.