Superficial Soft Tissue Tumors of the Skin Victor G. Prieto, MD, PhD Professor of Pathology and Dermatology Head of Dermatopathology UT-MD Anderson Cancer Center Houston, Texas
Summary • Introduction • Selected entities (update, clinical relevance, differential diagnosis) • Main Features: – Clinical – Histological – Immunohistochemical
Introduction • Spectrum: reactive to malignant (clinical relevance) • Objection of some purists • Almost any soft tissue tumor can occur in the skin (subcutaneous o subfascial) Skin biopsy
Atypical Fibrohistocytic Lesions • Classic concept: DF is a benign lesion completely different from DFSP, based on histologic and clinical features • Use of immunohistochemistry • But some times the differences are not so clear…
Atypical Fibrohistiocytic Lesions • Intermediate between DF y DFSP • Trunk, 0.6-2 cm, recurrence • Acanthosis and hyperpigmentation • Storiform pattern Horenstein et al. Am J Surg Pathol 2000; 24: 996-1003
• Keloidal collagen • Storiform pattern
• Keloidal collagen
• Infiltration of subcutaneous tissue
• Cellular atypia • Mitotic figures
FXIIIa
CD34
Key Points • The immunophenotype of these lesions suggests a differentiation between DF and DFSP • Possibility of local recurrence • Achieve complete excision
Epithelioid Fibrous Histiocytoma • Papule / nodule of 0.5 - 2 cm • Non pigmented or tan colored, elevated • Extremities in adults
• Dermal lesion, circumscribed • Collarette • No epidermal involvement
• Epithelioid cells, eosinophilic-clear • Regular nuclei with small nucleoli
• Focal keloidal collagen
S100 Protein
CD68
Factor XIIIa
Differential Diagnosis • Melanocytic lesions: – No pigment, no intraepidermal component – S100 protein- (dendritic cells!) – HMB45, MART1 – HAM56, (CD68)
Key Points • Include this entity among the differential diagnosis of unusual melanocytic lesions • Immunohistochemistry in case of doubt
Superficial Acral Fibromyxoma • Solitary mass on hands and feet • Asymptomatic
• 75-year-old white woman • Left palm lesion for 3 - 4 months • 1.7 x 1.5 cm • Asymptomatic, flesh-colored nodule
• Poorly circumscribed • Dermis • Spindle cells
• Close to epidermis • (No intraepidermal component
• Loose storiform pattern • Vascular
SMA
FXIIIa
CD34
Key Points • Adults • Same as cellular fibroma • Recurrence • DDx DFSP, DF
Epithelioid Sarcoma • Papule / nodule of 0.5 - 2 cm • Non pigmented or tan colored, elevated • Extremities in young adults
• 25 yo man • Soccer player (goalie) • Lesion started after trauma to the finger
• Ulcer • Acanthosis (~prurigo nodularis
• Central necrosis
Epithelioid cells Central necrosis
Distant metastasis (elbow)
Keratin
Differential Diagnosis • Granulomatous dermatitis: – Mucin (granuloma annulare) – Fibrin (rheumatoid nodule) – Multinucleated giant cells (necrobiosis lipoidica) – Keratin! – Loss of INI NI1 (SWI/SNF chromatin remodeling complex) Chr 22q11.2
Key Points • Include this entity among the differential diagnosis of unusual granulomatous dermatitides (young, fingers) • Immunohistochemistry in case of doubt
Plexiform Fibrohistiocytic Tumor • Uncommon neoplasm of intermediate malignancy • Dermis or subcutaneous tissue, on trunk and extremities in children and young adults Enzinger/ Zhang, Am J Surg Pathol 1988;12:818
• Infiltrative tumor, plexiform, small nodules • Short fascicules
• Infiltrative, plexiform, small nodules
Short fascicules with fusiform cells (fibroblasts y myofibroblasts) (sometimes the only component)
Macrophages and multinucleated giant cells (osteoclastic type)
Differential Diagnosis • Cellular DF / atypical fibrohistiocytic lesion • DFSP Both lack plexiform pattern or osteoclastic cells • Giant cell tumor of tendon sheath
Key Points • Children and young adults • Short fascicles of spindle cells • Macrophagic giant cells • Recurrent
Fibrous Hamartoma (of Infancy) • First year of life (23% congenital) • Axilla, arm, trunk, groin, and genital area • Solitary, asymptomatic, sometimes quick growth • t(6;12;8)(q25;q24.3;q13); t(2;3)(q31;q21) • Recurrence
Triphasic pattern: • Fascicles of fibroblasts • Adipocytes • Fusiform cells ( primitive mesenchyma)
Three components
Fusiform cells
Fascicles Mesenchyma/nerves
Differential Diagnosis • Neurofibroma • Giant cell tumor of tendon sheath
Key Points • Triphasic pattern • Similarities with neural lesions (neurofibroma, neurofibrosarcoma, schwannoma) • Negative for S100 protein
Neurothekeomas • Harkin and Reed (1969), Gallager (1980) • Superficial tumor of purported nerve sheath origin • Head and neck, extremities • Cellular and myxoid • Myxoid variant of the cellular type
• Dermal nodule • Fascicles
Myxoid background
Small cells, myxoid stroma
S100
Dermal nodule
Fascicles
Epidermis is spared
Uniform cells, fibromyxoid stroma
• Spindle, fusiform cells • Fibrous stroma
S100 A6
Ki67
Histologic Features • 25% moderate cytologic atypia (very rarely marked) • Mitotic figures 0 - > 10/mm2 • Pattern whorled or fascicular • Different amounts of myxoid background
IPOX Features • S100 in myxoid lesions (nerve sheath myxoma) • S100A6 in neurothekeoma • NKI/C3, CD10, microphthalmia transcription factor, and PGP9.5 • Focal expression of SMA and CD68
Key Points • Possibly two types (cellular/myxoid) • Myxoid variant of cellular NTK • S100 in the myxoid • S100 A6 in the cellular • Mostly non-aggresive • Careful with melanoma (S100)
Ossifying Fibromyxoid Tumor of Soft Tissue • Very rare, circumscribed • Deep nodules, slow growth • Trunk and extremities, 1 to 14 cm
• Fibrous capsule, ring of mature bone
• Fusiform or epithelioid cells • Irregular fascicles
• Myxoid areas
OFMST: Atypical Variant • 20% of cases show local recurrence!! • 10% distant metastases • Infiltrative border
Atypical variant
• Infiltrating border, hypercellularity, high nuclear grade, more than 2 mit/50 HPF
Key Points • Gross the hard areas at the periphery of the lesion • Mixture of fibrous and myxoid areas • Atypical variant
Pleomorphic Hyalinizing Angioectoid Tumor of Soft Parts • Firm, lobulated, tan, with focal hemorrhage, several cm in size • Lower extremity, middle age • Infiltrative, deep dermis and subcutaneous tissue • Local recurrence (50%)
• Loose connective stroma • Dilated vessels, hyaline ring
• Dilated vessels, fibrin
• Fusiform and epithelioid cells with pseudoinclusions • Pleomorphic cells (~ MFH) • Rare mitotic figures • Negative anti-S100
PHAT: DDx • Ancient schwannomas (dilated vessels with hyaline and nuclear pseudoinclusions) circumscribed, S100+ • MFH lacks hyalinized vessels, nuclear pseudoinclusions o CD34 expression. Numerous mitotic figures • Vascular tumors (hemangioma, hemangioendothelioma). CD31 and FVIIIra
S100 Protein
Key Points • Hyaline vessels • Nuclear atypia • Rare mitotic figures • Negative S100 protein
Acral Myxoinflammatory Tumor with Atypical Giant Cells • Inflammatory myxohyaline tumor of the extremities with virocytes or ReedSternberg cells • Inflammatory myxoid tumor of soft parts with atypical giant cells
AMTAGC • Rare, adults and older individuals • Distal extremities (hands and feet) • Frequent local recurrence (metastasis) • 1 - 6 cm • Clinical Dx: ganglion, tenosynovitis, giant cell tumor of tendon sheath
• Multinodular, infiltrative, ~hamartoma
• Fibrous stroma, pleomorphism
Key Points • Infiltrative • Mixed with adipose tissue • Large, virocytes • (Metastasis)
Soft Tissue Lesions in the Skin: Summary • At least five new lesions recently described • Possibility of local recurrence (even metastasis) • In case of doubt, complete excision
Pigmented Melanotic Schwannoma • Paraspinal • 20-50% recurrence or metastasis • Unclear histogenesis
C5, 36 yo man
• Infiltrating border, hypercellularity, high nuclear grade, more than 2 mit/50 HPF
• Psammoma bodies • Cytologic atypia
• S100 • MART1 • HMB45
Key Points • Melanoma in the wrong place • Rule out metastasis • Schwannian features (EM) • Recurrence and metastasis