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Penis and scrotum
Benign Tumors
Myointimoma
Editor: Antonio Cubilla, M.D. and Alcides Chaux, M.D. (See Reviewers page)
Revised: 16 May 2010, last major update May 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.
Definition
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● Benign myointimal proliferation with myxoid phenotype exclusively affecting corpus spongiosum of glans penis
Epidemiology
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● Very rare tumor with few reported cases (Am J Surg Pathol 2000;24:1524; Am J Surg Pathol 2007;31:1622)
● Mean age 29 years (range 2-61 years)
Sites
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● Glans
Etiology
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● Unclear if reactive or neoplastic
Clinical features
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● Small palpable nodular lesion on glans
● No recurrences reported, even in incomplete resections
Case reports
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● 50 year old man with nodule in glans (Pathol Int 2007;57:158)
Treatment
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● Conservative local excision; does not recur, even after incomplete excision
Gross description (Macroscopy)
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● 0.5 to 2 cm mass
Micro description (Histopathology)
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● Plexiform / multinodular pattern of growth
● Exclusive intravascular growth extending through vascular spaces of corpus spongiosum
● Atrophy of preexisting vessel walls and loss of vascular lumina
● Spindle and bland-appearing tumor cells with eosinophilic cytoplasm and indistinct cell borders (myofibroblast appearance)
● Intracytoplasmic vacuoles are common
● Surrounding stroma frequently showing myxoid/fibrotic changes
● Residual smooth muscle at the tumor periphery
● Also areas of degenerative changes with "ghost cell" morphology
Micro images
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Complex myointimal plexiform proliferation Increase in intravascular spindle cell
involving the corpus spongiosum buds on a fibromyxoid matrix
Positive stains
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● Alpha-smooth muscle actin, muscle-specific actin (HHF-35), calponin
Negative stains
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● CD31, CD34, Factor VII, S100, keratin
● Desmin (may have minimum staining)
Differential Diagnosis
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● Angioleiomoyoma (vascular leiomyoma): usually women, not in penis, often painful, smooth muscle cells surrounding vascular lumina
● Epithelioid hemangioendothelioma: very similar in morphology, very uncommon in penis, positive for CD31 and CD34
● Leiomyoma: predominant fascicular pattern of growth, rarely plexiform / multinodular, infrequent myxoid changes, desmin+
● Myofibroma: usually before age 2; does not affect penis; spindle cells arranged around thin walled branching vessels resembling hemangiopericytoma; usually calcification, necrosis
● Nerve sheath tumors (neurofibroma, schwannoma, nerve sheath myxoma): very uncommon in penis, less condensed myxoid matrix, positive for S100
● Nodular fasciitis, intravascular, late stage: intralesional inflammatory cells, expansion of vascular spaces, osteoclast-like giant cells, acellular mucoid pools
● Plexiform fibrohistiocytic tumor: usually women, extravascular, deep dermal or subcutaneous tumor with ray like extension into skeletal muscle or adipose tissue, spindle cells admixed with nodules of histiocytic cells, occasional osteoclast-like giant cells
End of Penis and scrotum > Benign tumors > Myointimoma
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