Once it was diagnosed as a dermatofibrosarcoma protuberans, the patient underwent an incisional fusiform biopsy. There was an absence of local symptoms and palpable lymph nodes. He described the onset as a small crusted papule that grew rapidly over the course of two weeks. The dermatological exam showed an erythematous tumoration in the lower left back, with firm consistency, and a bright and lobular surface, measuring about 15 cm at its longest axis. The extremely variable and nonspecific clinical appearance means its diagnosis is challenging.The authors report an exuberant case of desmoplastic melanoma, atypical in appearance and at an unusual location, with an initial diagnosis of dermatofibrosarcoma.Īn 83-year-old Caucasian male patient, a farmer by occupation, sought medical attention complaining of a "wound" located on the dorsum for eight months ( Figures 1 and 2). 1- 3 It is more frequent in males of advanced age (mean age = 66 years) and with a history of chronic exposure to the sun, which may explain its prevalence in sun-exposed areas, especially the head and neck (53.2%). The desmoplastic melanoma (DM) is a rare variant characterized by invasive proliferation of spindle cells in the dermis and variable degrees of stromal deposition of collagen (desmoplasia). It expresses a variety of phenotypes with different clinical and cytological variants, such as the extensive superficial, the nodular, the acral lentiginous and the lentigo maligna - which are the most classic - and the desmoplastic, the spitzoid and the amelanotic - which are the most unusual. Keywords: MELANOMA DIAGNOSIS HISTOLOGY IMMUNOHISTOCHEMISTRYĬutaneous melanoma is a malignant tumor located in the dermal-epidermal junction of the skin, arising from the atypical transformation of melanocytes. The authors present an exuberant case of desmoplastic melanoma in an unusual location, with an initial diagnosis of dermatofibrosarcoma. The extremely variable and nonspecific clinical appearance makes it a challenging diagnosis. It is more frequent in men of an advanced age having a history of chronic exposure to sunlight. Caution should be exercised in the interpretation of numerous actin-positive spindle cells in isolation of additional confirmatory or exclusionary data as desmoplastic melanomas may contain significant numbers of these cells.Desmoplastic melanoma is a rare variant of melanoma characterized by an invasive lesion of spindle cells and varying degrees of desmoplasia. Similarly, because of the variability in S100 expression in this neoplasm, the absence of S100 staining should not be relied on too heavily to exclude DMM if the clinical and histologic features favor that diagnosis. If a problematic spindle-cell skin lesion is a suspected melanocytic process, HMB45 is unlikely to provide confirmatory (or exclusionary) evidence for the diagnosis of DMM. This study indicates that the immunohistologic features of desmoplastic melanoma differ from those of conventional melanoma. Two color stains for SMA and S100 demonstrated that these smooth-muscle actin positive cells constituted a separate spindle-cell population, consistent with reactive myofibroblasts. In five cases, the number of actin-positive spindle cells. Nine (32%) DMM and DMM/SMM contained significant numbers of spindle cells immunoreactive for SMA but not desmin. CD68 staining was limited to < 5% of the spindle cells in two of 32 DMM and DMM/SMM and 20% of the cells in one of two SMM. Three DMM/ SMM were immunoreactive with HMB45, as were both SMM. All DMM were negative when stained with HMB45. S100 staining was limited to <</a> 5% of the spindle cells in two DMM/SMM. Thirty of 32 (94%) DMM and DMM/SMM were clearly positive for S100. Twenty-two (65%) cases were associated with a recognizable overlying pigmented lesion. Except for two cases, all were Clark's level IV or V. 11 were on the extremities, and six on the trunk. Seventeen cases occurred in sun-damaged skin of the head and neck. Patients ranged in age from 35 to 91 years (mean, 67) and included 23 men and 11 women. The clinical, histologic, and immunohistologic features of 22 desmoplastic melanomas (DMM), 10 mixed desmoplastic and spindle-cell melanomas (DMM/SMM), and two cellular spindle-cell melanomas (SMM) were studied.
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