Mercurial Metastatic Merkel Cell Carcinoma: A Case of Colonic Involvement

Abstract

Merkel cell carcinoma (MCC) is a neuroendocrine skin cancer that typically presents as a painless erythematous nodule on body surfaces visible to the sun. Metastatic disease is typical to the lymph nodes, liver, and lungs. There are previous case reports of patients with metastases to the gastrointestinal tract including the stomach, small intestine, and pancreas. To our knowledge, there are only rare occurrences of metastases to the colon. We report a patient with a history of MCC treated with chemotherapy who presented with hematochezia and underwent a colonoscopy that showed a partially obstructing, edematous, friable 7-cm circumferential mass in the transverse colon. Biopsy confirmed the diagnosis of MCC that metastasized to the transverse colon.

An Extraordinary Cause of Colonic Obstruction: Merkel Cell Carcinoma of Unknown Primary

“…To date, there have been 8 cases documenting existing or recurrent MCC metastatic to the colon (Table 1). 8–14 Our case is the first describing MCCUP of the colon, highlighting the need for awareness of MCC and MCCUP as a root cause of neuroendocrine tumor of the GI tract. In patients with an extensive cancer history or who may be immunocompromised, a thorough GI workup inclusive of biopsy and pathologic staining is necessary to distinguish a potentially insidious malignancy.…”

“…Previously described cases of MCC metastatic to the colon were not tested for MCPyV and were linked to a known cutaneous lesion. [8][9][10][11][12][13][14] Confirmation of metastatic MCCUP to rare sites of the colon is difficult because of low incidence, lack of primary lesion, and range of symptomatic presentations. Diagnosis of cutaneous MCC is confirmed by biopsy of a suspicious lesion with appropriate ancillary immunohistochemical studies correlated with imaging studies and possible lymph node biopsy.…”

“…Prior reports of GI involvement have highlighted metastasis most commonly to the stomach, but metastases to the colon are exceedingly rare. 8–14 To our knowledge, MCC metastatic to the colon has not been documented in the absence of a corresponding primary cutaneous lesion. Described is a patient who presented with bowel obstruction secondary to a large, circumferential hepatic flexure colon mass.…”