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90 year old Caucasian man with history of several non-

melanoma skin cancers, presented with a 4.0 x 2.5 cm

ulcerated, friable, exophytic mass on the left mid

frontal scalp of two months duration.

The patient had previously presented two months

earlier with non-healing scalp lesion. At that time, the

lesion was a 0.9 cm ulcerated, erythematous, papule. A

shave biopsy of the lesion was performed however the

histopathology was non-diagnostic and demonstrated

marked parakeratosis, fibrosing granulation tissue in

the upper dermis, with a massive neutrophilic infiltrate.

A repeat biopsy was performed of the exophytic mass

for diagnostic and de-bulking purposes. The

histopathology of the re-biopsy demonstrated an

ulcerated tumor filling the dermis. The tumor cells

were pleomorphic, spindled, arranged in vague

fascicles, and extended to the deep margin. The

cytology was markedly atypical, with large irregular

nuclei, prominent nucleoli, and numerous mitoses,

including atypical forms. Immunohistochemical

analysis was performed. The tumor cells were

diffusely positive for CD10 and weakly positive for

CD68. Cytokeratin AE1/AE3, desmin, S-100, EMA,

cytokeratin 5, p63, Mart-1, smooth muscle myosin,

procollagen 1, ERG, CD31, and CD 34 were all

negative.

History

Physical Exam

Figure 2-4. Histopathology of the lesion. The excision specimen

reveals the extent of tumor invasion. Tumor cells infiltrate the

dermis and the deep subcutis (H&E, 40X total magnification). The

tumor cells are spindled and arranged in vague interlacing fascicles

with focal areas of necrosis (H&E, 200X total magnification). The

tumor cells are pleomorphic with large, irregular nuclei, prominent

nucleoli, and moderately abundant eosinophilic cytoplasm. Mitoses

are readily identified, including atypical forms (H&E, 400X total

magnification).

Histopathology

The patient subsequently underwent wide local

excision with one centimeter margins. The specimen

showed atypical spindled cells extending deep into

subcutaneous tissue. Due to the depth of invasion with

involvement of subcutaneous tissue and the presence

of necrosis, the lesion was diagnosed as an

undifferentiated pleomorphic sarcoma of skin. The

margins were free of tumor however the patient was

referred to oncology for further evaluation and

consideration of adjuvant therapy. The patient and

family declined oncology referral, and as of four

months post-excision, there was no evidence of

recurrence.

Clinical Course

Discussion

Undifferentiated pleomorphic sarcoma (UPS) of skin

can clinically and histopathologically mimic atypical

fibroxanthoma (AFX). Distinguishing between the

two is important, as the prognoses of these tumors are

vastly different. AFX follows more of a benign course,

typically recurs only after incomplete excision, and

rarely metastasizes. UPS, previously grouped into the

malignant fibrous histiocytoma (MFH) category, is

more aggressive in nature, and has a high rate of

recurrence along with malignant/metastatic potential.

Clinically, AFX presents as a rapidly growing solitary

nodule on sun-damaged, actinic skin of the elderly,

usually on the head and neck region. UPS is

considered a soft tissue tumor but can occur

superficially in the skin, with a presentation mimicking

AFX.

Histologically, UPS and AFX consist of spindle shaped

cells arranged in a fascicular pattern and can exhibit

multinucleation, pleomorphism, and mitotic figures.

UPS is distinguished from AFX by deep subcutaneous

involvement, perineural and/or lymphovascular

invasion, and necrosis. Immunohistochemically, both

stain negative for S-100/SOX-10, cytokeratin,

CD31/CD34, and desmin/myosin allowing

differentiation from other pleomorphic tumors in the

skin, such as melanoma, squamous cell carcinoma,

angiosarcoma, and leiomyosarcoma. AFX and UPS

are diagnoses of exclusion, requiring broad lineage-

specific immunohistochemical analysis to exclude

other poorly differentiated tumors.

References

1. Bolognia JL, Jorizzo JL and Rapini RR. Fibrous and

fibrohistiocytic proliferations of the skin and tendons, atypical

fibroxanthoma. In: Dermatology, 3rd ed, Elsevier, 2012. p

1973.

2. Goldblum JR, Folpe AL and Weiss SW. Undifferentiated

pleomorphic sarcoma. In: Enzinger and Weiss's Soft Tissue

Tumors, 6th ed, Elsevier, 2014 p 421-442.

3. McKee PH, Calonje E and Granter SR. Connective tissue

tumors, atypical fibroxanthoma, malignant fibrous

histiocytoma. In: Pathology of the Skin, 4th ed, Elsevier, 2012.

p 1658-1662.

4. Luzar B and Calonje E. Morphological and

immunohistochemical characteristics of atypical fibroxanthoma

with a special emphasis on potential diagnostic pitfalls: a

review. J Cutan Pathol. 2010 Mar;37(3):301-309.

5. Miller K, Goodlad JR and Brenn T. Pleomorphic dermal

sarcoma: adverse histologic features predict aggressive

behavior and allow distinction from atypical fibroxanthomas.

Am J Surg Pathol. 2012 Sep;36(9):1317-1326.

6. Beer TW, Drury P, and Heenan PJ. Atypical fibroxanthoma: a

histological and immunohistochemical review of 171 cases. Am

J Dermatopathol. 2010 Aug;32(6):533-540.

7. Mirza B, and Weedon D. Atypical fibroxanthoma: a

clinicopathological study of 89 cases. Australas J Dermatol.

2005 Nov;46(4):235-238.

There is significant overlap between AFX and UPS of

skin clinically, morphologically, and

immunohistochemically. Histologically, there are

identifiable differences found on excision of the lesion.

Distinguishing the two requires complete excision to

evaluate for aggressive features, specifically the

tumor’s extent of invasion, with AFX designated to

tumors restricted to the dermis. UPS of skin invades

deeply into subcutaneous tissue and can demonstrate

tumor necrosis, perineural or lymphovascular invasion.

These features are consistent with its more aggressive

course including recurrence and metastatic potential.

Undifferentiated pleomorphic sarcoma is a rare entity

with confusing, misleading, and changing

nomenclature previously named malignant fibrous

histiocytoma. Undifferentiated pleomorphic sarcoma

of skin is a diagnosis of exclusion made after complete

excision with histology aided by

immunohistochemistry. The correct diagnosis is crucial

to optimal outcome, preventing mismanagement of an

aggressive and potentially fatal tumor.

Figure 1. Clinical presentation of lesion. Left mid frontal scalp

with rapid growing, ulcerated, 4 x 2.5 cm exophytic mass.

1 University of North Texas Health Science Center, Forth Worth, TX; 2 ProPath, Dallas, TX

Michael Carletti DO1, Peter Malouf DO1, Zachary Ingersoll MS-III1, Greg Hosler MD, PhD2, Stephen Weis DO1

Undifferentiated Pleomorphic Sarcoma of Skin: Clinical and histopathologic emulator ofatypical fibroxanthoma, distinction imperative