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Pleomorphic liposarcoma (PL) is an uncommon form of liposarcoma that rarely occurs in the skin and subcutis. As its behavior in this setting is incompletely characterized, we undertook a study of a series of superficial PLs, defined as those arising or based primarily in the dermis and/or subcutis without involvement of deep structures. In addition, MDM2 gene amplification, a diagnostic signature of well-differentiated/dedifferentiated liposarcoma (WDL/DL), was evaluated to address the recent observation that this gene is amplified within PL-like areas in DL. PLs were obtained from institutional and consultation files (n=29). Cases were evaluated with respect to age, sex, location (dermis, dermis and subcutis, subcutis), size, predominant pattern (pleomorphic spindled or epithelioid), extent of lipogenic differentiation, and tumor necrosis. MDM2 amplification was analyzed using FISH on formalin-fixed, paraffin-embedded material in 26 cases. Patients ranged in age from 5 to 93 years (M:F=1.4:1). Tumors were located on the extremity (n=15), trunk (n=7), and head and neck (n=7) and involved the dermis (n=4), dermis and subcutis (n=10), and subcutis (n=15). Tumor size ranged from 0.8 to 15 cm (median=2 cm). All were mitotically active high-grade sarcomas [FNCLCC grade 2 (n=23) or 3 (n=6)] with either a pleomorphic spindled (n=24) or an epithelioid pattern (n=5) with variable extent of lipogenic differentiation [25% (n=15), 25% to 50% (n=9),50% (n=5)]. Necrosis was present in 3 cases. MDM2 gene amplification was present in 3 of 26 cases. Follow-up information in 24 cases (range=1 to 192 mo; median=48 mo; mean=59 mo) revealed local recurrences (4/24) but no metastasis or death from disease. We conclude that cutaneous and subcutaneous PLs, despite their high grade, have a much more favorable outcome compared with their deep-seated counterparts, most likely attributed to their small size and superficial location. The low incidence of MDM2 gene amplification in our series indicates that most superficial PLs are unrelated to WDL/DL. PL likely evolves by way of more than 1 molecular pathway.

Sentinel lymph node (SLN) status currently represents the single most important prognostic factor in clinically localized melanoma and is widely used in patients with melanoma at significant risk for nodal micrometastasis. Although several studies have looked at the rates and implications of inaccuracies in the histopathologic diagnosis of melanocytic lesions, accuracy in the histologic interpretation of the SLN in melanoma has not been addressed. The goal of this study was to determine the rates of discordance in the histopathologic evaluation of the SLN and the potential clinical impact on patients referred to a comprehensive melanoma center.A prospectively collected database was queried for melanoma patients who had SLN biopsies performed at outside institutions before referral to the University of Michigan Multidisciplinary Melanoma Program between 2006 and 2009. These cases were reviewed and clinical follow-up obtained.After internal review of the SLN material, 13 (8 %) of 167 cases had major discrepancies in diagnosis that impacted patient management and prognosis. The disease of five patients was subsequently downstaged and the disease of eight patients was upstaged after internal review of the SLNs and reversal in diagnoses.There appears to be a small yet significant rate of discordance in diagnosis of the SLN for melanoma after expert histopathologic review. The implications of this discordance and revision of diagnosis is substantial. Expert histopathologic review of the SLN warrants consideration to provide the most accurate prognostic information and optimal patient care.

Basal cell carcinoma (BCC) is the most common nonmelanoma skin cancer. Most BCCs are found on areas of UV-damaged skin, The study of BCCs of sun-protected regions, however, suggests a more complex pathogenesis. We present a case of BCC of the perineum in a man with no previous history of skin cancer. This is the first report of BCC in this region and one of a small body of cases arising on or near the genital and perianal regions.

Low-grade fibromyxoid sarcoma (LGFMS) is a rare, typically deep-seated soft tissue neoplasm with deceptively bland cytology and metastatic potential. A t(7;16)(q34;p11) translocation, yielding a FUS/CREB3L2 fusion gene, has been identified in approximately 80%-90% of deep soft tissue LGFMS. Cutaneous fibromyxoid neoplasms occur not infrequently; dermatopathologists rarely consider LGFMS in the differential diagnosis, as this lesion is uncommon in the skin. We identified a group of superficial LGFMS and a spectrum of other cutaneous fibromyxoid neoplasms and performed fluorescence in situ hybridization (FISH) to assess the frequency of FUS rearrangement. FISH for the chromosomal rearrangement of FUS (16p11), using a dual-color, break-apart probe (Abbott Molecular/Vysis, Des Plaines, IL), was performed on formalin-fixed paraffin-embedded tissue sections from superficial LGFMS (n = 6), myxomas (n = 10), and myxofibrosarcoma/myxoid malignant fibrous histiocytomas (myxoid MFH) (n = 5). One hundred nonoverlapping tumor nuclei per case were evaluated for either fused (normal) or split (translocated) signals. Of the LGFMS, 4 of 6 (67%) showed a rearrangement of FUS (range: 72%-80% positive nuclei per 100 nuclei). The other neoplasms within the differential diagnosis were devoid of any rearrangement involving FUS (range: 0%-2% positive nuclei per 100 nuclei). Our observed frequency of FUS rearrangement in superficial LGFMS is consistent with those published in the literature for more deeply seated lesions. When applied to suspicious superficial myxoid or fibromyxoid neoplasms, the FUS FISH probe in formalin-fixed paraffin-embedded tissue can be a useful ancillary technique for diagnosis of this uncommon and deceptively bland tumor.