Sometimes with true glandular formation • Round vesicular nuclei with prominent nucleoli • Abundant clear cytoplasm May contain intracytoplasmic melanin • Absence of intercellular bridges • Paget cells often extend to adnexal structures • Flattened…
Haphazard arrangement Thin fascicles rather than solid growth pattern No atypia No mitoses No necrosis Immunohistochemistry (+) for muscle markers Top Differential Diagnoses • Cutaneous leiomyoma (pilar leiomyoma) Occurs in adults…
Also associated with organ transplantation, systemic steroids, and leukemia Clinical Issues • Occurs in both adults and children • Can involve any cutaneous site; uncommonly involves mucosal sites, deep soft tissues • Typically…
Located centrally within lobules • Basaloid/germinative cells at periphery of lobules • Cytologic atypia not prominent • Presence of mitotic figure in germinative layer does not indicate malignant potential Ancillary Tests • Sebocytes express…
Apocrine differentiation is usually seen Often with decapitation secretion • Outer layer of cuboidal myoepithelial cells • Variable degree of mitotic index Top Differential Diagnoses • Syringocystadenoma papilliferum (SCP) Similar histologic features, indicating…
Deep subcutaneous/fascial/muscular extension, necrosis, &/or lymphovascular invasion Shows no identifiable line of differentiation (i.e., diagnosis of exclusion) • Synonyms: Superficial malignant fibrous histiocytoma, undifferentiated pleomorphic sarcoma of skin Clinical Issues • Older…
Presence of keratocysts allows for distinction (absent in eccrine carcinoma) • Adenoid cystic carcinoma Cribriform architecture allows distinction (generally absent in eccrine carcinoma) • Infiltrative basal cell carcinoma Lacks true lumen formation…
Only a few cases have metastasized, usually to lymph nodes and lungs Macroscopic • Usually a few centimeters, can be up to 8 cm Microscopic • Composed of infiltrative lobules, islands, and…
No nuclear β-catenin labeling but cytoplasmic labeling common • Inclusions show granular &/or filamentous features by EM • Cytoplasmic filaments extend onto inclusions Infantile Digital Fibromatosis/Inclusion Body FibromatosisClinical examination of infantile digital…
Cutaneous müllerian cyst Eccrine cutaneous ciliated cyst Etiology/Pathogenesis • Müllerian (paramesonephric) heterotopia • Metaplasia of sweat gland epithelium Clinical Issues • Cutaneous müllerian cyst: Typically affects limbs of young female patients • Eccrine cutaneous…
