Diffuse Large B-Cell Lymphoma, Leg Type
~ 85% of all cases • Subset of cases arise in skin of other sites (trunk, arms, head and neck) ~ 15% of cases • Single or multiple lesions at time of…
Adult T-Cell Leukemia/Lymphoma
Epidermotropism &/or Pautrier microabscesses • Peripheral blood with multilobated “flower cells” • Lymph nodes with effaced architecture & diffuse infiltrate • Bone marrow with patchy involvement & increased osteoclasts Ancillary Tests • Confirmation of…
Trichoblastoma
Can be multiple in some cases • Rare recurrences and association with, or progression to, malignancy [basal cell carcinoma (BCC)] Macroscopic • Nodular lesion involving deep dermis and subcutis • Large, typically >…
Condyloma Acuminatum (Genital Wart)
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…
Granular Cell Tumor
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,…
Leiomyosarcoma
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:…
Acral Lentiginous Melanoma
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…
Desmoplastic Melanoma
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…
Nevi of Special Sites
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…
Cutaneous Gamma-Delta T-Cell Lymphoma
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…
