Dermatofibrosarcoma Protuberans, Genitourinary Tract
Locally aggressive spindle cell fibroblastic tumor of intermediate malignancy.
Dermatofibrosarcoma protuberans (DFSP) is a rare neoplasm (estimated incidence between 0.8 and 5 cases per one million population per year), but represents the most frequent superficially located sarcoma
Usually adults between 20 and 50 years, but can rarely occurs in infants and children
Slight male predominance
The trunk, the proximal extremities, and head and neck region are the most common involved sites. To the best of our knowledge, in male genital organ DFSP has been described in scrotum (1 case) and penis (6 cases). Only one testicular metastasis is reported in English literature.
Wide surgical resection with excision of subcutaneous fat (2–3 cm margins) in order to prevent recurrence. Imatinib therapy (tyrosine kinase inhibitor) is the gold standard for treatment of inoperable, metastatic, or recurrent DFSP.
DFSP has an extremely high tendency for local recurrence after a limited resection. Only rare cases of metastasis in organs and regional lymph nodes have been reported (<0,5%). Progression to fibrosarcoma can rarely occur.
Nodular, polypoid, or plaque-like neoplasm centered in dermis. The size is extremely variable (mean size 5 cm) and the color is generally gray-white, but may appear brown or black if melanocytes are present. Hemorrhage and necrosis are rarely seen.
Most observed variants: myxoid, atrophic, granular, sclerosing, and pigmented (Bednar’s tumor, rich in pigmented melanocytic cells).
Positive: CD34 (strong and consistently in 95%), vimentin, actin (focal), and CD99 (can be weakly positive).
Negative: S-100 (except in Bednar variant), HMB-45, Factor XIIIa (usually), keratin, EMA, desmin, and CD117.
DFSP presents a t(17;22)(q21;q13) translocation or a supernumerary ring chromosome derived from the translocation r(17;22). The translocation results in the fusion of exon 2 of PDGFB to various exons of the COL1A1 gene related to collagen type 1 alpha 1 gene and platelet-derived growth factor beta chain.
Dermatofibroma is also a storiform lesion, but it is noninfiltrative. Moreover, it is less cellular than DFSP and shows polymorphous cellular infiltrate. Factor XIIIa is positive and CD34 negative. Pleomorphic undifferentiated sarcoma and atypical fibroxanthoma presents also a storiform pattern, but also moderate to severe cellular pleomorphism and nuclear atypia.
The pigmented variant (Bednar’s tumor) must be distinguished from desmoplastic melanoma which, however, lacks storiform pattern, displaces or destroys fat, shows dense collagenous stroma, and is CD34 negative and S-100 and SOX10 positive.
References and Further Reading
- Abdulfatah, E., Chaudhry, R., Bandyopadhyay, S., & Qureshi, F. (2016). Myxoid dermatofibrosarcoma protruberans of the scrotum: A rare diagnosis in an unreported location. Human Pathology: Case Reports., 6, 40–44.Google Scholar
- Patel, K. U., Szabo, S. S., Hernandez, V. S., Prieto, V. G., Abruzzo, L. V., Lazar, A. J., & López-Terrada, D. (2008). Dermatofibrosarcoma protuberans COL1A1-PDGFB fusion is identified in virtually all dermatofibrosarcoma protuberans cases when investigated by newly developed multiplex reverse transcription polymerase chain reaction and fluorescence in situ hybridization assays. Human Pathology, 39(2), 184–193.CrossRefGoogle Scholar
- Peard, L., Cost, N. G., & Saltzman, A. F. (2018). Dermatofibrosarcoma protuberans in a male infant. Urology. pii: S0090-4295(18)31135-X. https://doi.org/10.1016/j.urology.2018.08.050. [Epub ahead of print]