Case of the Week

Editor: Mahmut Akgul (akgulm@amc.edu)

2022-21/May 23

Contributors: Daniel Athanazio, Paulo Roberto Fontes Athanazio

A teenager noticed a nodule in the dorsal side of the penis two years before this presentation. The nodule was surveilled clinically. In this period, no skin lesions were noted. In the last months, the lesion rapidly grew causing ulceration in dorsal skin and invading corpora cavernosa and corpus spongiosum (as evaluated by imaging studies).

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5 photo(s) Updated on: May 20, 2022

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Quiz

1. What is the correct diagnosis?

a) Penile osteosarcoma

b) Sarcomatoid squamous cell carcinoma of the penis

c) Giant cell tumor of soft tissue

d) Melanoma with osteosarcomatous differentiation

e) Paraffinoma/Sclerosing lipogranuloma

f) Sarcomatoid urothelial carcinoma of the urethra

The entire tumor is submitted to microscopic evaluation. Few areas suggestive of osteoid production were noted. Microscopically, atypical mononuclear cells are diffusely positive for SATB2 (a marker of osteoblastic differentiation), CD99, and vimentin. These cells are negative for pan-keratin, SOX10, S100 and ERG. Desmin is focally expressed. CD68 is expressed only in multinucleated giant (osteoclast-like) cells. Among high-grade soft tissue sarcomas, SATB2 expression can be used as an indicative of extraskeletal osteosarcomas with poor matrix production(WHO 2022). This tumor also showed focal areas of weak p63 expression. Rather than evidence of squamous differentiation in this case, we interpret this feature as expected in giant cell tumors (both bone and soft tissue primaries) and osteoclast-rich osteosarcomas.

Primary penile extraskeletal osteosarcomas are exceedingly rare. A recent report showed also the feature of osteoclast-rich areas. The same is true for extraskeletal osteosarcomas of other sites.The main differential diagnosis in this case would be melanoma with osteosarcomatous differentiation and sarcomatoid carcinoma. Melanoma is ruled out by absent expression of S100 and SOX10. Sarcomatoid carcinoma should also be considered in the differential diagnosis,but the patient experience a long term growth of a palpable nodule with no relationship with the penile skin or the urethra. The dorsal skin was ulcerated after recent rapid growth. The urethra was uninvolved in the resection specimen, even though the erectile tissue of corpus spongiosum was infiltrated. Pan-keratin was negative. P63 expression -as discussed above -cannot be used in the differential between squamous carcinoma and giant cell rich tumors of soft tissue. In addition, sarcomatoid squamous cell carcinoma is typically an HPV-independent neoplasm that are much more common in older patients.

We also considered the possibility of metastatic osteosarcoma. Imaging of the skeleton, however, showed no suspicious bone lesions.

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About GUPS

The Genitourinary Pathology Society (GUPS) was formed with the vision of advancing the care of patients with urologic diseases through enhancements of best practices, research, and education in the subspecialty of Urological Pathology.

GUPS is an official Companion Society of the United States and Canadian Academy of Pathology (USCAP).

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