Cutaneous Metastatic Rectal Adenocarcinoma in Zosteriform Distribution.

Abstract

Dear Editor: A 54-year-old woman presented with mildly stinging, painful, grouped nodules on the left vulvar area. It shows unilateral localized grouped papulonodular lesions, resembling a zosteriform aspect (Fig. 1). The patient had a history of stage IV rectal adenocarcinoma with liver and lung metastases treated 17 months earlier with ultra-low anterior resection and chemotherapy. The patient also received external pelvic irradiation of 180 cGy/day, up to total 6,300 cGy/35 fractions, for recurrent adenocarcinoma at the anastomosis site. She presented with a zosteriform eruption on the left vulvar area during hospitalization, with no prior history of herpes zoster. The skin lesions exhibited predominantly nodular infiltration, inadequate for the tzanck test. A skin punch biopsy was performed under the differential diagnosis of herpes zoster on the left S2 dermatome, postherpetic granuloma, and cutaneous metastasis. Histopathology revealed metastatic adenocarcinoma (Fig. 2). The chest computed tomography (CT), abdomen CT, and positron emission tomographic-CT images showed consistent results of an increasing size of lung and hepatic nodules with lymph node metastasis. Pain around the vulva area was aggravated after repetitive chemotherapy and radiotherapy. Wide excision was performed to resect the visible cutaneous nodules with patient consent. The patient died eight months after the diagnosis of cutaneous metastasis, which was three years after the initial diagnosis of rectal adenocarcinoma. While the mean survival time from the diagnosis of cutaneous metastasis of colorectal cancer is 18 months1, our patient died in a shorter time span. Cutaneous metastasis from an internal malignancy is rare and can appear in many different forms, including the multiple nodular type, inflammatory or erysipeloid form, sclerodermoid form, alopecia neoplastica, or bullous form. The nodular type is the most common clinical appearance, while the zosteriform pattern is very rare2. The exact mechanism of zosteriform cutaneous metastasis is unknown. A Koebner-like phenomenon at the site of herpes zoster, invasion of the perineural lymphatic or dorsal root ganglion, direct invasion of tumor cells, and accidental surgical implantation have all been proposed 2,3. Colonofiberscopy and magnetic resonance imaging revealed an ulcerated fungating mass located on the left posterolateral wall of rectum. The metastatic lesion of the vulva was observed about 17 months later after a laparoscopic resection. However, an asymptomatic skin lesion may have appeared earlier. It is possible that the metastatic skin lesions may have been due to direct seeding of the tumor cells to the left side, but the exact mechanism remains unclear. The patient was undergoing chemotherapy when the metastatic lesions were observed, and herpes zoster occurs more frequently in immunosuppressed patients. It has been reported that many patients with cutaneous metastasis of zosteriform distribution are initially misdiagnosed with herpes zoster and treated with antiviral drugs4. Considering the pain and unilaterality, this may be easily misdiagnosed as herpes zoster. Herein, we report an unusual case of cutaneous metastasis of rectal adenocarcinoma that mimicked herpes zoster. This must be considered in any patient with a history of malignant neoplasm experiencing non-healing zosteriform lesions. Therefore, early biopsy for suspicious skin lesions is very important. Fig. 1 Stinging painful erythematous grouped nodules on the left vulvar area. Fig. 2 Dermal infiltration by intestinal type atypical glands, showing metastatic skin adenocarcinoma (H&E, ×100).