title: Primary cutaneous histiocytoid carcinoma with distant metastasis.
abstract: Distinguishing primary cutaneous adnexal carcinoma from metastatic carcinoma of unknown primary can be a diagnostic challenge due to the frequent overlap of histologic and immunohistochemical features. A 58-year-old man presented with a tender, indurated plaque on axillary skin. Biopsy revealed infiltrating atypical cells throughout the dermis, without connection to the epidermis. Tumor cells had a histiocytoid appearance and displayed mild pleomorphism. The tumor was discohesive and had areas with a single file pattern. Signet ring cells were also present. Cells were reactive with CK7, CK5/6, p63, GATA3, GCDFP-15 and Her 2-neu. Additional studies were negative, including TTF-1, CDX2, E-cadherin, mammaglobin, estrogen receptor and progesterone receptor. Thorough clinical and radiologic evaluation failed to identify an occult primary extracutaneous malignancy; however, regional lymphadenopathy, widespread osteoblastic lesions and multiple subcentimeter liver hypodensities were noted. Considering the clinical and histopathologic features, the diagnosis of primary cutaneous histiocytoid carcinoma with distant metastasis was favored.
authors.affiliation: Department of Dermatology, The University of Texas Medical Branch, Galveston, Texas.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Philips
authors.affiliation: Department of Dermatology, The University of Texas Medical Branch, Galveston, Texas.
authors.forename: Leila
authors.initials: L
authors.lastname: Langston
authors.affiliation: Department of Pathology, The University of Texas Southwestern, Dallas, Texas.
authors.forename: Helena
authors.initials: H
authors.lastname: Hwang
authors.affiliation: Department of Dermatology, The University of Texas Southwestern, Dallas, Texas.
authors.forename: Travis
authors.identifier: http://orcid.org/0000-0001-6577-3838
authors.initials: T
authors.lastname: Vandergriff
authors.affiliation: Department of Dermatology, The University of Texas Medical Branch, Galveston, Texas.
authors.forename: Tanya
authors.initials: T
authors.lastname: Trynosky
authors.affiliation: Department of Dermatology, The University of Texas Medical Branch, Galveston, Texas.
authors.forename: Alma C
authors.initials: AC
authors.lastname: Berlingeri-Ramos
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D020405:Dermis / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000378:metabolism*; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins
keywords: Her 2-neu; metastatic carcinoma; primary adnexal carcinoma; primary cutaneous histiocytoid carcinoma; tumor