Atypical fibroxanthoma

Atypical fibroxanthoma
Diagnosis in short
Atypical fibroxanthoma. H&E stain.
LM	dermal lesion with marked nuclear atypia, mitoses, mulitnucleated cells, cell have foamy cytoplasm
LM DDx	malignant melanoma, pleomorphic undifferentiated sarcoma, leiomyosarcoma, sarcomatoid squamous carcinoma
IHC	S-100 -ve, CK34betaE12 -ve, p63 -ve, desmin -ve
Site	skin - see skin tumours, usu. head & neck
Clinical history	rapid growth, elderly
Prevalence	uncommon
Prognosis	good
Clin. DDx	malignant skin tumours
Treatment	complete excision

Atypical fibroxanthoma, abbreviated AFX, is poorly differentiated skin tumour with likeness to undifferentiated pleomorphic sarcoma.

General

• Typically head & neck region.
• Thought to be related to pleomorphic undifferentiated sarcoma; some say it is the same thing.
• Usually benign.
  • May metastasize - case report-type of occurrence.

Clinical:

• Rapid growth.
• Elderly.
• Good prognosis.

Microscopic

Features:

• Dermal lesion - key point.
• Marked nuclear atypia.
• Mitoses.
• Mulitnucleated cells.
• Foamy cytoplasm - key feature.

DDx:

• Malignant melanoma.
• Pleomorphic undifferentiated sarcoma (MFH) - deeper than the dermis.
• Leiomyosarcoma.
• Sarcomatoid squamous carcinoma.

Notes:

• No Grenz zone. (???)

Images

• 

  AFX. (WC)

• 

  AFX. (WC)

• 

  AFX. (WC)

www:

• AFX (cdlib.org).

A markedly atypical lesion of far less worrisome significance is the pleomorphic hyalinizing angioectatic tumor of soft parts (subcutis).
Pleomorphic hyalinizing angioectatic tumor of soft parts (subcutis). A. The key distinction is at low power, wherein cluters of thin-walled, indented (ectatic) blood vessels are seen. B. The ectatic vessels have a thin endothelial lining and a thick subjacent rim of amorphous eosinophilia. Note the multinucleated cells in the stroma. C. Hyaline material extends beyond vessels to entrap stromal cells. D. Cellularity in part raises the possibility of a sarcoma. E. High power further raises the suspicion of malignancy, given the aberrant nuclei with prominent nucleoli. F. Reassurance occurs because 1) there are virtually no mitoses, 2) there is no necrosis, and 3) there are readily identifiable nuclear inclusions as seen in these tumor cells.

IHC

Features:

• S100 -ve (done to r/o melanoma).
• CK34betaE12 -ve.
• p63 -ve (done to exclude SCC).
  • Scant staining not considered +ve.
• Desmin -ve (done to r/o leiomyosarcoma).
• CD99 +ve.
  • Usually +ve in melanoma... but negative in squamous carcinoma.

Others:

• Vimentin +ve.
• SMA +ve.^{[citation needed]}

New et al. suggests:

• Vimentin, SMA, CD68, cytokeratins, p63, desmin, CD99, CD10, S100, CD117, LN-2, procollagen I.

A panel:

• Vimentin, SMA, CD68, CK18, EMA, CAM5.2, CK34betaE12, CK5/6, p63, desmin, CD99, CD10, S100, CD34.

Sign out

Incompletely excised

SKIN LESION, MID BACK, SHAVE BIOPSY:
- ATYPICAL SPINDLE CELL NEOPLASM, SEE MICRO AND COMMENT.

COMMENT:
The diagnosis of atypical fibroxanthoma (AFX) is favoured.  The main differential
diagnosis is pleomorphic undifferentiated sarcoma.

The extent of the lesion cannot be determined, as it is present at the deep margin.

This lesion should be re-excised, as it could represent an aggressive malignancy.

See also

• Dermatologic neoplasms.
• Undifferentiated pleomorphic sarcoma.