Isolated Cutaneous Metastasis to Forearm as a Presenting Feature of Colon Adenocarcinoma

Cutaneous and subcutaneous metastasis from colon cancer is an uncommon occurrence, with an incidence of 4 to 6.5% [1]. The most frequent site of cutaneous metastasis in colonic cancer is the previous surgical scar [2]. Metastasis to skin carries a dismal prognosis and usually occurs in the setting of widespread and disseminated disease [1]. However, remote cutaneous metastasis without evidence of other visceral metastasis has also been reported in the literature [3]. Cutaneous metastases are usually metachronous, that is, they are detected after the diagnosis of the primary tumor [4, 5]. Occasionally, synchronous cutaneous metastases develop in colon cancer [6, 7]. We present a case of synchronous cutaneous metastasis to forearm, without evidence of any other visceral metastasis, in a patient subsequently diagnosed with adenocarcinoma of colon.

A 65-year-old male presented with a gradually increasing lump in the left forearm for 3 months. Physical examination demonstrated a hard irregular lump measuring 4 cm x 3 cm with a nodular surface and well-defined margins (Figure 1). The lump was fixed to the skin but was freely mobile on the underlying structures. Overlying skin color was normal. Patient did not have any clinically apparent lymphadenopathy. Fine needle aspiration of the lump was reported as metastatic adenocarcinoma. A detailed evaluation revealed that the patient was anemic and had a history of loss of weight and appetite since 6 months. There was no history of bleeding per rectum. Rest of the physical examination was unremarkable except for the asthenic look of the patient. Fecal occult blood test was positive. An upper gastrointestinal endoscopy was normal; however, on lower gastrointestinal endoscopy, an ulcero-proliferative growth was found in the ascending colon and cecum. Histopathological examination of growth biopsies confirmed the diagnosis of colon adenocarcinoma. Carcinoembryonic antigen (CEA) levels were elevated. Contrast enhanced CT scan of chest, abdomen and pelvis found a T2 disease with no distant metastasis. A bone scintigraphy scan was negative. In the presence of a solitary cutaneous metastatic lesion and resectable tumor based on radiological and clinical evidence, a decision to proceed with surgery was taken. An extended right hemicolectomy and resection of the cutaneous lesion was performed without any serious complication. Histopathology of the colonic specimen reported T3 N2 poorly differentiated

signet cell adenocarcinoma with negative proximal and distal margins. Histopathology of the cutaneous lesion also revealed poorly differentiated signet cell adenocarcinoma with negative margins (Figure 2). On immunohistochemistry, the cutaneous metastasis was positive for cytokeratin (CK) 20 and negative for CK 7 that confirmed its colonic origin (Figure 3, 4). The patient recovered uneventfully from surgery and received 6 cycles of FOLFOX as adjuvant chemotherapy. Seventeen months after the surgery, patient presented with hemoptysis. A contrast enhanced chest and abdominal CT scan showed pulmonary and liver metastases that were confirmed by cytology.