Mixed Bag for Monday, April 7th, 2025

History

9 year old, healthy girl with firm nodule inferior and lateral to left nipple.  Has been there for years, nontender, but may have increased in size.

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Question

The lesion has more than doubled in size in 3 year interval. There is some skin thickening, but no redness or inflammation. What is the most likely diagnosis?

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Correct answer

giant cell fibroblastoma

Discussion

The lesion has a broad base along the dermis and homogenously increased echotexture, poorly defined margins, and minimal color Doppler flow.  Histologically it showed spindle cell proliferation extending from the dermal layer with positive CD34 stain and occasional multinucleated giant cells.  Giant cell fibroblastoma belongs to the same category as dermatofibrosarcoma protuberans, but is considered to be at the benign end of the spectrum.  The lesion is known to recur locally if not completely resected.  This is a rare, locally aggressive tumor, known to affect children, median age of 6 years, most often involving the trunk, groin, and axilla. It is characterized by multinucleated giant cells, spaces that resemble blood vessels (pseudovascular spaces), and a specific genetic fusion involving the COL1A1 and PDGFB genes.  Subsequent genetic testing was positive in this case.

Differential diagnosis

Fibroadenoma should be a smoothly marginated, hypo to isoechoic ovoid lesion, often with thru transmission.  It is not broad based against the dermal layer of skin and may vary in size and tenderness with hormonal cycles in post pubertal girls.   Breast abscess would be expected to show hyperemia, heterogenous echotexture with fluid components, and a different/acute time course.  Metastatic lesions are typically round to ovoid, well circumscribed, well perfused, and seen in patients with known primary cancers.

References

• https://curesarcoma.org/sarcoma-subtypes/giant-cell-fibroblastoma/ https://app.statdx.com/document/dermatofibrosarcoma-protuberans/8fb1d01f-9511-467c-a74b-dd011b0b0533?term=giant%20cell%20fibroblastoma%20breast&searchType=documents&category=All&documentTypeFilters=all https://app.statdx.com/document/fibroadenoma/0dd5d128-68c7-4bef-bf6a-f2d71b1bbc49?term=giant%20cell%20fibroblastoma%20pediatric%20breast&searchType=documents&category=All&documentTypeFilters=all