New or unusual dermatopathology tumors: a review

As experience is acquired, there is a constant evolution in both terminology and understanding of various relatively newly described tumors in the realm of dermatopathology. Several mesenchymal tumors of the lower extremity have undergone various changes in nomenclature, molecular discoveries, and histologic grading. Examples include hemosiderotic fibrohistiocytic lipomatous lesion/pleomorphic hyalinizing angiectatic tumor; superficial acral fibromyxoma; and myxoinflammatory fibroblastic sarcoma. Primary cutaneous myoepithelioma is also a relatively newly described entity for which grading and classification continue to evolve. Finally, even our understanding of the classic granular cell tumor has expanded to include a non-neural variant. This article reviews the current nomenclature, emerging concepts, and differential diagnosis of these evolving entities.