Case Number : Case 4144 - 08 Dec 2022 Posted By: Saleem Taibjee

Pleomorphic fibroma

This tumor looks like a giant cell fibroblastoma of childhood, but in adult and with polypoid silhouette, fits well the above diagnosis. So agree with Anil. 

Yes, agree.

Here are some immunos....

Superficial CD34+ fibroblastic tumour (SCFT) mimicking pleomorphic fibroma!

Not the typical location, but with those IHCs...spindle cell/pleomorphic lipoma. Great case! :)

Will go with pleomorphic fibroma

Soft tissue tumours are not my forte, and I am grateful for expert review by Dr Will Merchant on this case. The pertinent immunostains show positive staining for androgen receptor and possible loss of RB1 within the spindle cell and multinucleated cell population. We did also arrange FISH for MDM2 which showed no evidence of amplification, tending to rule out atypical lipomatous tumour/sarcoma.

Although not specific, positive staining for androgen receptor has been described in spindle cell lipoma/pleomorphic lipoma spectrum Frequent detection of androgen receptors in spindle cell lipomas: an explanation for this lesion's male predominance? - PubMed (nih.gov)

and cytogenetic findings including loss of RB1 are summarised here Cytogenetics of Spindle Cell/Pleomorphic Lipomas: Karyotyping and FISH Analysis of 31 Tumors - PubMed (nih.gov)

There is certainly an increasing recognition that pleomorphic lipoma and pleomorphic fibroma are probably lesions on the same spectrum, with some cytogenetic data to support this, RB1 loss also described in pleomorphic fibroma. Loss of retinoblastoma in pleomorphic fibroma: An immunohistochemical and genomic analysis - PubMed (nih.gov)

Happy New Year!

Saleem