Irregular wrinkled nuclei Bi- and multinucleation Perinuclear vacuolization • Old lesions may mimic seborrheic keratoses Ancillary Tests • Immunostain for p16 is negative (there is no overexpression) • In situ hybridization and PCR…
Female predilection More prevalent in African Americans • Wide anatomic distribution, usually arises in skin and subcutaneous tissue Head and neck region common (tongue, oral cavity) • Usually solitary, painless nodule, plaque,…
Lesions restricted to cutis only rarely metastasize Microscopic • Perpendicularly oriented fascicles of spindle cells • Brightly eosinophilic cytoplasm • Blunt-ended nuclei • Nuclear atypia and mitoses Ancillary Tests • Labels as per smooth muscle:…
Rare to absent in early lesions, prominent and confluent in late lesions Nests are irregular in size and shape, randomly alternate with single melanocytes • Cells show elongated, ovoid hyperchromatic nuclei…
HMWCKs(+), p63; S100(-) • Atypical fibroxanthoma S100(-); CD10/CD68/CD99 (+) • Dermatofibroma: FXIIIA/CD10 (+); S100(-) • Dermatofibrosarcoma protuberans: CD34(+); S100(-) • Neural tumors S100/SOX10 (+); CD34(+) (not in DM) • Leiomyosarcoma Actin/desmin (+), S100(-) Scar-Like Appearance…
Displaced Junctional Nests in Breast NevusAt this low power, a junctional melanocytic proliferation is evident on the breast of a 25-year-old woman. Most nests appear at the tips of rete…
Malignant T cells rim around adipocytes Prominent karyorrhexis/apoptosis and angioinvasion Ancillary Tests • Immunohistochemistry: TCRδ1(+), βF1(-), CD56(+), CD4(-), CD8(-) • EBER(-), cytotoxic markers (+) • T-cell receptor gene rearrangement Top Differential Diagnoses • Subcutaneous…
Pilar type (piloleiomyoma) arises from arrector pili Genital type arises from specialized genital smooth muscle Etiology/Pathogenesis • Hereditary leiomyomatosis and renal cell cancer syndrome Multiple leiomyomas of skin and uterus Subset…
Inflammatory component shows variable mixtures of lymphoplasmacytic cells, eosinophils, neutrophils, and histiocytes • Areas with prominent myxoid change • Scattered enlarged atypical tumor cells, some with macronucleoli Cells with macronucleoli resemble Reed-Sternberg…
