22 April 2008 – Case of the Week #116
To view the images or references,
you must click on the links in blue. Links in green are to journals with free full text-no
registration.
This email is sent only to
subscribers. To subscribe or
unsubscribe, email NatPernick@Hotmail.com,
indicating subscribe or unsubscribe to Case of the Week. There is no charge. We do not sell, share or use your email
address for any other purpose. We also
have free email subscriptions for Pathologist/PhD jobs (biweekly), Other
laboratory jobs (biweekly), website news (monthly) and new books
(monthly). Email us to subscribe.
We have established The Detroit College
Promise, a program to provide tuition scholarships for
We thank Dr. Keloth E. Pradeep,
Case of the Week #116
Clinical
History
A 60 year old man had a pearly
papular lesion of the scalp.
Micro images: low power
- #1; #2; high power - #3; #4
Immunostains: vimentin,
Factor
XIIIA, CD68,
keratin,
MelanA
What is your diagnosis?
Diagnosis:
Epithelioid variant of benign
fibrous histiocytoma
Discussion
This uncommon variant of benign fibrous histiocytoma (dermatofibroma) usually presents as a small (1 cm or less), solitary, elevated nodule in the extremities. The mean age is 42 years (Br J Dermatol 1989;120:185). It is composed of uniform, medium to large, angulated epithelioid cells, often perivascular, with overlying epidermal effacement (AJSP 1994;18:583). There is minimal inflammation, and no prominent giant cells. The phenotype is predominantly myofibroblastic and not histiocytic. These tumors are immunoreactive for Factor XIII, but negative for CD68 and CD163. They may arise from the dermal microvascular unit (J Cutan Pathol 2003;30:415).
The differential diagnosis includes solitary
epithelioid histiocytoma, Rosai-Dorman disease and granulomatous
conditions. This case most closely
resembles solitary epithelioid histiocytoma, a recently described lesion
formerly called reticulohistiocytoma (AJSP 2006;30:521).
It is composed of large epithelioid histiocytes, but with abundant dense
eosinophilic and glassy cytoplasm, often with spike-like cytoplasmic extensions. The nuclei are round/oval with distinct
nucleoli. Unlike this case, there are
variable nuclear grooves and multinucleated cells, and frequent lymphocytes and
neutrophils. There is some overlap with
epithelioid variant of benign fibrous histiocytoma regarding the staining
pattern, as the histiocytes are immunoreactive for vimentin, and may have focal
staining for Factor XIIIA. They are also
immunoreactive for CD163, CD68 (may be focal), and negative for MelanA, S100
and keratin.
Rosai-Dorfman disease usually
presents with multiple skin lesions and adenopathy. Its histiocytes are pleomorphic, with
emperipolesis and S100 staining. There
are also prominent B cells and plasma cells.
Granulomas also contain epithelioid histiocytes, but they are in well
formed clusters and are surrounded by lymphocytes.
Malignant lesions to consider
include melanoma (tight clustering of cells, S100+, HMB45+), epithelioid
sarcoma (deep seated, granuloma-type clusters with necrosis, more atypia,
keratin+, CD163-), and histiocytic sarcoma (marked atypia and mitotic activity)
Epithelioid variant of benign
fibrous histiocytoma has an excellent prognosis, with only rare recurrences reported
after excision.
Nat Pernick, M.D., President
PathologyOutlines.com, Inc.
Bingham Farms,
Telephone: 248/646-0325
Email: NatPernick@Hotmail.com
Alternate email: NatPernick@gmail.com