Regressing seborrheic keratosis - clinically and dermoscopically mimicking a regressing melanoma

The diagnosis of seborrheic keratosis is a clinical diagnosis. In a certain percentage of cases, differential diagnosis between seborrheic keratosis and malignant melanoma is difficult. We describe a case of regressing seborrheic keratosis simulating malignant melanoma. Clinical, dermoscopic and histopathologic examinations were performed for the occurrence of an asymmetric, irregularly demarcated, irregularly pigmented lesion measuring 1.3 x 1.5 cm on the right part of the abdomen in a 76-year-old male Caucasian. In order not to miss melanoma, the excision and histopathologic examination of the lesion with peppering is essential.     

Clinically and dermoscopically featureless melanoma: when prevention fails

We report a case of amelanotic melanoma that was clinically and dermoscopically featureless; it was repeatedly missed during examination at a pigmented lesion clinic. Dermoscopy evidenced a peculiar vascular pattern, and only the adoption of a specific diagnostic algorithm including the atypical vascular pattern among the major diagnostic criteria would have helped the observer make the correct diagnosis. The risk of false-negative diagnosis by both clinical examination and dermoscopy during melanoma screening as well as the possible role of dermoscopy in the diagnosis of amelanotic melanoma are discussed.     

Giant melanoacanthoma mimicking malignant melanoma

Melanoacanthoma denotes a rare variant of pigmented seborrheic keratosis. A 65-year-old male farmer had pigmented, verrucous, itchy, highly painful, progressively growing irregularly oval plaque on left side of lower back for the past five years. The indurated lesion, measuring maximum diameter 10 cm × 5 cm, had no discharge, bleeding, ulceration, or associated lymphadenopathy. Dermoscopy showed regular pigmentary network and cribiform pattern of ridges without any feature of malignant melanoma. Histopathology showed well-defined islands of basaloid cells interspersed with large and richly dendritic melanocytes. The lesion was totally excised followed by skin grafting. Our patient was unique in its massive size and clinical resemblance with malignant melanoma. The diagnosis was confirmed by dermoscopy and skin biopsy.     

The Atrophic Dermatofibroma: A Delled Dermatofibroma

Atrophic dermatofibroma has been proposed as a term to designate a new and specific type of dermatofibroma. We report the clinical and histopathological findings in two cases of atrophic dermatofibroma. The peculiar morphology of these lesions simply represents a conspicuous example of the frequently seen central depression in dermatofibroma. On histopathology, no authentic atrophy is present, because the thinning of the dermis compared with that of the adjacent non-lesional skin results from this depression rather than from loss of tissue of the dermis. Delled dermatofibroma is a more appropriate appellation than atrophic dermatofibroma, because of the striking shape of these lesions.     

Dermatofibroma lenticulare

Ohne ZusammenfassungMit 3 Textabbildungen.     

Subcutaneous Dermatofibroma

Dermatofibroma (DF) is usually confined to the dermis and the overlying epidermis is usually hyperplastic. Although DF with deep subcutaneous extension is commonly encountered, purely subcutaneous DF is uncommon. In this review, we describe a case of a 41-year-old male patient who presented with a painless, subcutaneous, hard papule on the left thigh. After the skin had been incised the lesion was totally removed, and histopathology revealed a subcutaneous dermatofibroma.     

Alpha-interferon induced sarcoidosis mimicking metastatic melanoma

Despite its modest potential benefit, alpha-interferon is one of the most frequently employed therapies for melanoma. With the increasing incidence of melanoma, a parallel increase in interferon use and the associated adverse reactions that accompany interferon therapy should be expected. We present a case of an interferon-induced sarcoidosis-like reaction in a melanoma patient that was initially misinterpreted clinically and radiographically as metastatic melanoma. The etiology of sarcoidosis remains a mystery, but appears to involve Th-1 cytokines such as interferon and interleukin-2. Observance of a sarcoidosis-like reaction induced by interferon therapy lends additional support to the importance of this cytokine in the pathogenesis of sarcoidosis. It is important for pathologists to be aware of this entity when interpreting biopsies from melanoma patients treated with interferon.     

Epidermotropic xanthoma mimicking balloon cell melanoma

Xanthomas of the skin may mimic balloon cell melanoma because 1) both lesions may exhibit a diffuse dermal proliferation of cytologically similar large vacuolated or clear cells with distinct cytoplasmic membranes, 2) dermal maturation (smaller deep dermal nuclei) is absent in both lesions, 3) melanin pigment is usually absent in balloon cell melanoma, 4) cellular atypia may be minimal in balloon cell melanoma, and 5) mitoses may be absent or rare in balloon cell melanoma. We report a unique xanthoma, which further simulated melanoma by exhibiting epidermotropism and a pseudonesting pattern at the dermal-epidermal junction. The correct diagnosis was made with an immunohistochemical panel revealing tumor cell positivity for CD68 and negativity for S-100 protein and MART-1. Immunohistochemical studies may be required in the critical differential diagnosis of epidermotropic xanthoma and amelanotic balloon cell melanoma.     

Congenital Spitz nevus clinically mimicking melanoma

The differentiation between atypical variants of Spitz nevus and melanoma is often difficult given the many clinical and histopathologic similarities between the two. We report a case of an infant with a congenital scalp lesion exhibiting clinical features of melanoma, including variegation and regression of pigmentation and a rapidly changing appearance. Histologic examination of the excised lesion revealed a benign congenital Spitz nevus. This case emphasizes the need for clinical and histologic correlation in determining the benign or malignant nature of atypical pigmented lesions in infants.     

Pigmented poroid neoplasm mimicking nodular melanoma

We reported the case of a 92‐year‐old woman with a pigmented and non‐pigmented surface of the pedunculated nodule on her lower leg. Microscopic examination revealed that this nodule consisted of a component of small, dark, homogenous, poroid cells and cuticular cells in the dermis. The histopathological features of the lesion were consistent with poroid neoplasm. Immunohistochemistry showed that HMB‐45 and Melan‐A were positive in malanocytes and melanophages of the pigmented areas. Unlike most poroid neoplasms, this case showed pigmented lesion mimicked nodular melanoma.     

Macrophage-rich epithelioid angiosarcoma mimicking malignant melanoma

BACKGROUND: Cutaneous epithelioid angiosarcoma is a type of cutaneous angiosarcoma and usually arise both on the head or neck of the elderly. CASE REPORT: An 86-year-old male with an epithelioid angiosarcoma of the scalp that mimicked malignant melanoma. RESULTS: A large irregular dark grey-blue plaque with an adjacent speckled tan nodule was suggestive of a primary cutaneous malignant melanoma with adjacent in-transit metastasis. Both had a well-circumscribed growth pattern and were composed of numerous large epithelioid cells with scattered severe atypia and mitoses. The tumor was positive for S-100 protein and vimentin and negative for low- and high-molecular weight cytokeratins. However, at high power, the epithelioid cells with severe atypia were negative for S-100 protein, and abundant large epithelioid macrophages were responsible for the S-100 protein positivity. The malignant tumor cells were negative for HMB-45, positive for CD31 and Factor VIII-related antigen, and focally positive for CD34. A focus of infiltrative, classical angiosarcoma with irregular vascular channels lined with plump, anaplastic endothelial cells was then found deep to the epithelioid tumor. CONCLUSIONS: Macrophage-rich epithelioid angiosarcoma demonstrates abundant S-100 protein-positive epithelioid macrophages. This subset of epithelioid angiosarcoma may mimic malignant melanoma and may present as a pitfall in diagnosis.     

Blue naevus with satellitosis mimicking malignant melanoma

Blue naevus is an acquired benign melanocytic naevus. It is a firm, sharply defined dark blue to grey-black papule or nodule, which is likely to arise from the arrested dermal melanocytes in the dermis. In the last few years, blue naevus has attracted much attention due to the recognition of new entities and to its confusion with malignant melanoma. We report a 69-year-old man who developed a blue-black nodular lesion with satellitosis on his scalp. Although clinically it was thought to be a malignant melanoma, histopathological investigation and conservative methods such as dermatoscopy and power Doppler ultrasonography did not confirm this diagnosis. Histopathological examination excluded malignant melanoma, as there were no cellular atypia and mitotic activity in either the nodular lesion or the satellitosis. Doppler ultrasonography confirmed the benign nature of the lesion. Dermatoscopic examination showed homogeneous steel-blue pigmentation with individual blue globules, dots and some brown veils, and confirmed the histopathological diagnosis. To the best of our knowledge, our case is the third reported case of a blue naevus with satellitosis mimicking malignant melanoma.