Abstract

A 62-year-old man presented with a 1.2cm plaque to the vertex scalp and a 0.6cm papule to the right forehead. Both lesions were pink and dome-shaped with a central hemorrhagic crust. The patient subsequently presented with chest pain and a large lung mass. Skin biopsies demonstrated pleomorphic cells in the dermis arranged in cords dissecting around thickened/hyalinized collagen fibers. The lesional cells were characterized by vacuolated-eosinophilic cytoplasm, vesicular chromatin, and inconspicuous nucleoli. Lesional cells expressed p63, CK7, SOX10, cytokeratin MNF116, and EMA. PAX8, RCC, CD10, androgen receptor, CAIX, melan-A, CK20, and TTF-1 were negative. FISH was positive for EWSR1 gene rearrangement. EWSR1-ATF1 fusion was confirmed by next generation sequencing. Biopsy of the lung mass showed similar histopathologic and immunophenotypic features. Hyalinizing clear cell carcinoma (HCCC) was initially described as a minor salivary gland neoplasm. Morphologic features are typically low-grade, as seen in our patient. EWSR1-ATF1 fusion is consistently identified in HCCC. Interestingly, our patient presented with a primary lung HCCC (PLHCCC) with skin metastasis. To our knowledge, only 13 cases of PLHCCC have been reported previously.  This is the first reported case of cutaneous metastasis by PLHCCC. This entity is difficult to diagnose and has many histologic mimics, including squamous cell carcinoma. EWSR1-ATF1 fusion detection is a helpful ancillary test for diagnosis. The prognosis is favorable following surgical resection. Neoadjuvant chemotherapy and post-operative radiotherapy have been utilized for high-risk lesions.  It is important for dermatopathologists to be aware of a diverse range of metastatic neoplasms to better guide patient management.