COW-2019-24

CASE OF THE WEEK

2019-24 / JULY 29
(CONTRIBUTOR: JOHN CHEVILLE)

26-year-old male presents with a “fibrous plaque” of the penis associated with curvature. The patient undergoes surgery for presumed Peyronie’s disease at which time the surgeon excises the plaque material. The tumor is Keratin-positive. The immunostain shown is INI-1.

Quiz

1. What is the most common site of involvement of penile sarcomas?
a. Glans
b. Foreskin
c. Shaft
d. Penile urethra

 

2. What sarcoma does not occur on the penis?
a. Angiosarcoma
b. Rhabdomyosarcoma
c. Epithelioid sarcoma
d. None of the above.

 

3. What is the most useful immunohistochemical panel in this setting?
a. Keratin, desmin, SOX10, actin
b. Keratin, desmin, INI-1, S100
c. Keratin, actin, melan A, HMB45
d. Keratin, CD45, CD30, S100

1. c
2. d
3. b

1. Shaft
2. None of the above
3. Keratin, desmin, INI-1, S100

Any sarcoma can involve the penis, and the most common sarcomas are malignant vascular tumors including angiosarcoma and Kaposi sarcoma. The next most common tumor is leiomyosarcoma. Epithelioid sarcoma of the penis is rare with fewer than 20 reported cases. These tumors present as penile plaques and have been clinically interpreted as Peyronie’s disease. These tumors usually occur in men younger than 40 years of age, and treatment usually requires radical surgery for localized disease. In the diagnostic work-up, immunostains for keratin and INI-1 are diagnostic. These tumors are keratin positive and lose INI-1. INI1 is a member of the SWI/SNF chromatin remodeling complex on chromosome 22q11.2, and epithelioid sarcoma shows loss of INI-1. Although in this case, the specimen was fragment, one could identify the nodular configuration of the tumor with central necrosis/degeneration.

Hornick JL, Dal Cin P, Fletcher CD. Loss of INI1 expression is characteristic of both conventional and proximal-type epithelioid sarcoma.
Am J Surg Pathol 2009;33:542-550.

John Cheville
Mayo Clinic, Rochester
cheville.john@mayo.edu

Penis

Epithelioid sarcoma, INI-1, penile sarcoma