COW-2021-42

1. b

Angiomyofibroblastoma-like tumor

Microscopic examination shows a relatively circumscribed proliferation of bland spindle and stellate shaped cells (Figure 2) with alternating hyper and hypocellular areas (Figure 3) in a background of myxoid stroma. Prominent vasculature with hyalinized vessel walls were noted (Figure 4). Stroma has some areas with delicate collagen bundles. Interspersed vague nodular growth is appreciated. Mild perivascular and stromal lymphocytic and lymphohistiocytic infiltration is present with scattered mast cells. Immunohistochemical assays with appropriate controls show the tumor cells are diffusely positive androgen receptor, focally positive for desmin with weak focal CD34 and progesterone positivity (Not shown); and negative for S100 (S100 highlights background mast cells), SOX-10, STAT6, SMA and pan NTRK.

This case has morphologic (bland spindle cells with stellate cytology, alternating hyper and hypocellular areas, vessels with different calibers) and immunophenotypical (AR positivity, desmin focal positivity, focal CD34 positivity is also reported) features suggesting an angiomyofibroblastoma-like tumor.

AMF-like tumor is very rare benign lesion with rare reports of invasion or recurrence. Grossly, these tumors are superficial with a gray-white to yellow-brown cut surface. Histologically, they show prominent vessels with perivascular hyalinization with a bland spindle cell proliferation with short bundles of wispy collagen with no significant atypia or mitotic activity. A small amount of fat can be seen. IHC the spindle cells are S-100 negative, Vimentin Positive and variably positive for CD34, SMA, Desmin, and muscle-specific actin.

AMF-like tumors in males differ than their counterparts in females by occurring at an older age and they show a more spindle morphology than epithelioid-like more commonly seen in females. Aggressive angiomyxoma, is an important differential. It’s a very rare entity than can be seen in the scrotal region. It shows infiltrative borders with minimally atypical spindle cells in a myxoid background with surrounding small clusters of smooth muscles and numerous thick walled vessels. Another differential, solitary fibrous tumor, can be differentiated by The presence of keloid like collagen and stag-horn vessels as well as the positivity of STAT-6. Another low-grade spindle cell neoplasm, fibrous pseudotumor (nodular periorchitis), is third most common scrotal extratesticular mass after lipoma and adenomatoid tumor. It’s associated with prior inflammation or trauma, and histologically shows a dense hyalinized collagen with scattered psammoma bodies and scattered lymphoplasmacytic inflammatory infiltrate.

Iwasa Y, Fletcher CD. Cellular angiofibroma: clinicopathologic and immunohistochemical analysis of 51 cases. Am J Surg Pathol. 2004;28(11):1426-1435. doi:10.1097/01.pas.0000138002.46650.95

Msakni I, Ghachem D, Bani MA, et al. Paratesticular Angiomyofibroblastoma-Like Tumor: Unusual Case of a Solidocystic Form. Case Rep Med. 2017;2017:1273531. doi:10.1155/2017/1273531

Ding G, Yu Y, Jin M, Xu J, Zhang Z. Angiomyofibroblastoma-like tumor of the scrotum: A case report and literature review. Oncol Lett. 2014;7(2):435-438. doi:10.3892/ol.2013.1741

Wolfman DJ, Marko J, Gould CF, Sesterhenn IA, Lattin GE Jr. Mesenchymal Extratesticular Tumors and Tumorlike Conditions: From the Radiologic Pathology Archives. Radiographics. 2015;35(7):1943-1954. doi:10.1148/rg.2015150179

Hasan Basri Aydin, Mahmoud Aldyab, Mahmut Akgul
Albany Medical Center Department of Pathology and Laboratory Medicine, Albany, NY

Testis

testis, low grade spindle cell neoplasm, angiomyofibroblastoma-like, paratestis