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Merkel cell carcinoma (MCC) is an uncommon malignant neuroendocrine tumour that typically presents as indurated dermal nodules in elderly patients. MCC presenting as subcutaneous nodules is rare and the biological behaviour is not well characterized. We report here a case of MCC presenting as inguinal subcutaneous masses with subsequent epidermotropic metastasis. CASE REPORTA 77-year-old man presented to our clinic with bilateral painless inguinal subcutaneous masses and a pubic nodule. The patient first noticed the right inguinal lump 3 years previously, and the left groin mass developed a year later. One year previously a pubic nodule appeared with bleeding on palpation. Thus the patient sought medical advice.On physical examination, the two inguinal subcutaneous tumours were mobile with normal overlying skin, and measured 5 and 3 cm in diameter, respectively. The pubic nodule measured 2.5 × 1.8 × 0.8 cm. The base was mildly erythematous, but not indurated (Fig. 1).The pubic tumour was excised and the histopathology revealed an exophytic tumour composed of sheets and nests of uniform cells with epidermotropism. Focal lymphatic invasion was noted without perineural involvement. The mitotic figures were high (10/10 high-power field), but no tumour necrosis was found. The tumour cells were positive for cytokeratin (CK) 7, neuronespecific enolase, chromogranin, synaptophysin, and negative for CK 20, thyroid transcription factor (TTF-1) and thrombomodulin (Fig. 2). A core biopsy from the right inguinal mass revealed tumour cells of similar cytology in a myxoid stroma.Whole-body computer tomography, abdominal sonography, colonoscopy, and panendoscopy showed only subcutaneous inguinal masses and gastritis. The serum biochemistry was unremarkable, except for hyperuricemia. Metastatic carcinoid of unknown primary was initially diagnosed. Because of the indolent nature of the inguino-crural tumours, he refused further treatment.During follow-up, the tumours on the inguinal areas enlarged gradually and several thumb-tip-sized tumours appeared on the previous surgical site. After 2 years, computer tomography showed multiple nodules in both lower lung fields with pleural effusions, marked soft tissue masses encasing the bilateral external iliac vessels extending down to bilateral inguinocrural areas, and hypervascular papillary tumours at the base of the penis. A diagnosis of neuroendocrine carcinoma with cutaneous metastasis was subsequently made. Multiple spinal metastases developed one year later. He died of pneumonia 30 months after first diagnosis of this carcinoma. Throughout the history, he did not show any carcinoid symptoms and his 24-h urinary 5-hydroxyindoleacetic acid (5-HIAA) was normal. DISCUSSIONThe three main differential diagnoses of our case included MCC, carcinoid tumour, and metastatic small cell lung carcinoma (SCLC). SCLC was excluded because of the negative result of TTF-1 stain and the long-latency between the inguinal masses and the subsequent systemic metastasis. A diagnosis of metastatic carcinoid...

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Given its relative rarity, acroangiodermatitis is often misdiagnosed clinically. It can simulate a number of diseases such as Kaposi sarcoma, angiokeratomas, lichen planus, pigmented purpuric dermatosis, lichen aureus and stasis dermatitis. The dermoscopic appearance of acroangiodermatitis, that is, the presence of many irregularly distributed polymorphic vessels and white structureless areas correlates with proliferating capillaries and dermal fibrosis, respectively. On the other hand, a dermoscopy of Kaposi sarcoma shows a homogeneous pink-mauve pattern, red-bluish-purple areas and a rainbow pattern in macular, papular and nodular lesions, respectively 2,3 Angiokeratomas have characteristic regular dark lacunae on dermoscopy 4 while pigmented purpuric dermatosis has a coppery-red background pigmentation on dermoscopy. 5 The vascular proliferation in Kaposi sarcoma is independent of the underlying normal vasculature, unlike in acroangiodermatitis. Moreover, fibroblastic activity often accompanies the vascular proliferation in acroangiodermatitis (white areas in dermoscopy) which helps in its differentiation.

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