Interesting Case of Skin Metastasis in Colorectal Cancer and Review of Literature

Skin metastasis is a complication rarely seen after curative resection for colorectal cancer and chemotherapy. The article describes a metachronous case of skin metastasis after curative resection. This article is presented to illustrate that genetic and molecular profiling of carcinoma is a must for diagnosis of aggressive biological behavior and that skin metastasis is usually a harbinger of adverse outcome.


Introduction
Cutaneous metastases though rare may be the earliest manifestation of metastatic colorectal cancer. Such metastasis often indicates a poor prognosis, with the situation being further complicated by suboptimal treatment and aggressive biological behavior of such tumors.
A 25-year-old male patient presented with a history of bleeding per rectum, mucus discharge, and features of intestinal obstruction for 3 months. He was positive for Hepatitis B surface antigen (HBsAg); the exact etiology of which was unknown. On physical examination, rectal examination revealed semicircumferential growth involving 6 cm from anal verge 9-3 o'clock position. HPE was suggestive of poorly differentiated carcinoma. Colonoscopy was not passible due to stenosis. Carcinoembryonic antigen (CEA) levels were 1.3 ng% (<5 ng%). Contrast-enhanced computerised tomography (CECT) (Figure 1) showed irregular circumferential thickening of the wall of the rectosigmoid junction narrowing lumen, 15 cm in length from 6-19 cm with pericolonic and perirectal fat stranding. Hence, a diversion colostomy was done and the patient was subjected to long course chemoradiation with cisplatin and 5-fluorouracil and after 8-week interval, restaging was done. Per rectal, examination did not reveal palpable tumor. Imaging ( Figure 2) done showed only wall thickening at the lower rectum without evidence of enlarged lymph nodes. Serum CEA was 1.7 ng% (n < 5 ng%); low anterior resection was done using CDH31 stapler and diversion ileostomy was done. HPE revealed complete regression of tumour in the tissue studied. The patient was put on adjuvant chemotherapy. Two months later, he developed multiple cutaneous nodules on the chest and back (Figure 3). FNAC was suggestive of adenocarcinoma. Two months later, he developed multiple peritoneal metastases and succumbed to the disease a month later.
Skin involvement is seen in about 5% of patients with colorectal cancer [1] where it appears as subcutaneous or intradermal small nodules, and it can be confused with cysts, lipomas, neurofibromas, or alopecia due to these characteristics [2,3].
In an autopsy series of review of cutaneous metastasis from internal carcinoma [6,7], the most common primary site is the breast followed by the lung. The rectum is a very rare site and the most common site of metastasis was the previous surgical scar followed by the pelvis, back, chest, upper extremities, head, and neck [5]. Most of the cutaneous metastases are well-differentiated and mucin-secreting [7]. Several mechanisms of cutaneous metastasis have been postulated including lymphatic or hematogenous spread, direct extension, or implantation during surgery [2].
Skin involvement that can be seen at the time of diagnosis or during the course of treatment is a sign of advanced stage ( Table 1). The prognosis is generally poor with survival of about 18 months [2] with a general range of about 1-34 months [10]. Surgical biopsy may not be logical for these      patients due to poor survival and FNA cytology may be accurate for diagnosis of skin metastasis in a patient with known malignancy [11]. Wide local excision of the cutaneous metastatic lesion is the preferred treatment option in isolated lesions which is quite rare. Multiple cutaneous metastases are only palliated due to dismal prognosis [7].

Consent
Consent of the next of kin was obtained prior to the preparation of manuscript.

Conflicts of Interest
The authors declare that they have no conflicts of interest.

Authors' Contributions
Amarjothi JMV and Villalan R were responsible for the conceptualization, data curation, and formal analysis. Jeyasudhahar J and OL NaganathBabu were responsible for investigation, supervision, validation, and visualization and for the writing of the original draft, review, and editing.