Department of Pathology, Western General Hospital, University of Edinburgh, Edinburgh, Scotland.
Adv Anat Pathol. 2014 Mar;21(2):108-30. doi: 10.1097/PAP.0000000000000009.
Pleomorphic neoplasms are typically associated with high-grade malignant behavior, but this does not readily apply to primary cutaneous tumors. Despite morphologic features suggestive of malignancy, atypical fibroxanthoma, the classic example of a pleomorphic dermal neoplasm, is characterized by indolent clinical behavior. Atypical fibroxanthoma is a distinctive clinicopathologic disease affecting sun-damaged skin of elderly males. Histologically, it is often ulcerated and dermal based with pushing growth, characterized by a sheet-like and fascicular growth of pleomorphic epithelioid, spindled, and multinucleated tumor cells with brisk and atypical mitotic activity. However, no positive discriminatory histologic or immunohistochemical features exist. Its diagnosis is one exclusion with a wide differential diagnosis, mainly including other mesenchymal, melanocytic, and epithelial neoplasms. Particular considerations are pleomorphic dermal sarcoma, invasive melanoma, squamous cell carcinoma, metaplastic carcinoma, poorly differentiated cutaneous angiosarcoma, cutaneous leiomyosarcoma, myxofibrosarcoma, variants of fibrous histiocytoma (FH), pleomorphic fibroma, and non-neural granular cell tumor. The behavior of these tumors is varied and ranges from outright malignant to entirely benign, requiring confident diagnosis to reliably predict behavior and guide treatment. Although challenging, because of significant clinical and pathologic overlap, it is usually possible to establish a definitive diagnosis when attention is paid to the often subtle differentiating features. This requires careful tumor sampling, recognition of the subtle distinguishing morphologic features, judicious use and analysis of immunohistochemistry, and interpretation of the findings in the appropriate clinical setting.
多形性肿瘤通常与高级别恶性行为相关，但这并不适用于原发性皮肤肿瘤。尽管形态学特征提示恶性，但典型的多形性真皮肿瘤——非典型纤维黄色瘤，其临床行为呈惰性。非典型纤维黄色瘤是一种独特的临床病理疾病，影响老年男性日晒损伤的皮肤。组织学上，它通常为溃疡性和真皮起源，呈推挤性生长，由多形性上皮样、梭形和多核瘤细胞呈片状和束状生长为特征，具有活跃和非典型的有丝分裂活性。然而，不存在具有阳性鉴别意义的组织学或免疫组织化学特征。其诊断为排他性诊断，具有广泛的鉴别诊断，主要包括其他间叶、黑色素细胞和上皮性肿瘤。特别需要考虑的是多形性真皮肉瘤、侵袭性黑色素瘤、鳞状细胞癌、间变性癌、分化不良的皮肤血管肉瘤、皮肤平滑肌肉瘤、黏液纤维肉瘤、纤维组织细胞瘤（FH）的变体、多形性纤维瘤和非神经颗粒细胞瘤。这些肿瘤的行为多种多样，从完全恶性到完全良性，需要明确的诊断来可靠地预测行为并指导治疗。尽管具有挑战性，但由于存在显著的临床和病理重叠，当注意到通常细微的鉴别特征时，通常可以建立明确的诊断。这需要仔细的肿瘤取样、识别细微的鉴别形态学特征、明智地使用和分析免疫组织化学，并在适当的临床环境中解释这些发现。
