UPMC Dermatopathology "Case of the Month" Presentations
UPP - Department of Dermatology, Dermatopathology Unit
Case Authors: Peggy Lin MD, Leena T. Lourduraj MD, Drazen M. Jukic MD PhD
MAY 2005 CASE OF THE MONTH
DISCUSSION & DIAGNOSIS
Diagnosis
Atypical plexiform fibrohistiocytic tumor
Clinicopathologic
Epidemiology: Most patients have been reported to be between 2 months to 71 years of age.1,4 Females being affected more than men (3:1), 1,5,6 though some report equal frequency between females and males.4 Lesions of atypical plexiform fibrohistiocytic tumors usually occur on the upper extremities (63.1%) 1,3,4 of patients younger than 20 years. 1,3,4 Median age in one study was 14.5 years. 1 There is no reported racial predilection.1,3
Lesions of the upper extremity were reported as elbow, forearm, wrist, hand, and shoulder. 1,5 Other locations of the body of lower frequency were the head and neck and the back and chest wall. 1,5 The chin was the affected location in one 71 year old patient 1 and one 10 year old patient. 6 Most lesions are solitary, though multiple lesions have been associated in a case of recurrence. 1
The neoplasm typically presents as a solitary, firm, rubbery, and deep-seated
nodule. (1) Overlying skin is not discolored or ulcerated, but may be slightly
raised or show a slight central depression. (1,4) Growth of the tumor is most
often slow, though both growth spurts of the lesion or minimal to no growth have
been reported. (1) A history of preceding trauma is reported in only a few cases.
(1) There is often no pain nor tenderness associated with the lesions.(1,2)
Prognosis: Biologic behavior is unpredictable(5) with recurrence
rates are reported as 23%,2 37.5%, (1,2) and 40%, (4) usually in the first 2
years of diagnosis. 1,4 This tumor has also been reported to metastasize to the
lymph nodes in a few cases (3-6.2%). 1,2 Recurrence has been reported to occur
between 3 to 24 months 4 and up to 36 months in one study.( 1) The tumor has
even been reported to occur twice in one case(.4) Recurrence was observed to
occur prior to metastasis. Metastasis is not reported to go to the lung or other
organs.( 1) Because of the possibility of recurrence and metastasis, it is important
to discern these tumors from benign fibrohistiocytic tumors, such as dermatofibromas
and fibrous xanthomas.( 6)
Histology: Tumors are mostly located in the lower dermis(1)
at the dermal-subcutaneous junction4, although one case of recurrence occurred
in the superficial dermis(.4) Neoplasms of this type have also been reported
to extend into the subcutis or muscle. (1) On section, the lesion is reported
to have a gray-white to gray-tan color and the surface having irregular, dense,
gray-white trabeculae.(1) Reported lesions ranged in size from 0.3 to 6 cm.
(1,2)
The neoplasm is composed of nonencapsulated4 and poorly demarcated1 nodules with
slightly lobulated and irregular borders. (1) Cellular composition varies1 and
fascicles are composed of mononuclear and multinucleated plump spindle (4) cells
with histiocytic (43%) (1,4) and fibroblastic (17%) (1) features. Some report
cell types being round or oval cells with granular cytoplasm and a vesicular
nucleus or as elongated spindle cells. (3) Cells arrange in a plexiform fashion,
with some tumors reported to infiltrate into skeletal muscles. (1,2,4) Vascular
invasion has been reported in recurrent lesions. (1)
Tumor fascicles are of various sizes, which anastomose randomly, and trap normal
tissue in between them, giving the plexiform or reticulated appearance. (4) Histiocytic
nodules have been reported to appear as confluent nodular aggregates(4) or as
multifocal histiocytic nodules mixed with fibroblastic trabeculae. 4 Mild atypia
and mitoses may be observed. (1,3) Multinucleated and osteoclast-like giant cells
have been reported by some. (1) Other features that may been seen are microhemorrhage,(1)
dense fibrosis with hyalinization at the periphery,1 hemosiderin deposition,(1,2)
and a chronic inflammatory infiltrate.(1) The tumor mostly affects the mid to
deep dermis and the upper subcutis, and generally does not affect the upper dermis,
though it has been reported.(1) Overlying epidermis is usually not affected,
but may display acanthosis.(1) Extension to muscular tissue may occur.(1) Vascular
invasion has been described.(4) Tumor necrosis is generally not present.(1) Recurrent
lesions usually show the same pattern as the originally excised tumor.(1)
Immunohistochemistry reveals myofibroblastic differentiation, expressing positivity
for smooth muscle actin 1,2 and vimentin1 and negativity for S-100 protein, (1,2,4)
desmin, (1,2,4) cytokeratin,1 or Factor VIII-related protein.1 Positivity for
CD 68 is also seen.(2-4) Expression of a-1-antitrypsin and a-1-antichymotrypsin
is seen in one-third of cases, which supports fibrohistiocytic lineage.(1)Factor
XIIIa positivity was not reported in all cases.(4)
Differential diagnosis: Includes benign fibrous histiocytoma
(1,3,) plexiform neuroma, (1) fibromatosis, (1) benign and malignant giant cell
tumor, 1 and fibrous hamartoma.(1) Benign fibrous histiocytoma has a more cohesive
and uniform appearance, rather than the characteristic plexiform and multinodular
pattern and is usually located on the lower extremities. 4 Myofibroblastic differentiation
is suggested with positivity for smooth muscle actin.(3( Negativity for factor
XIIIa suggests that this tumor is not of dermal dendrocytic lineage. (3) Fibrous
histiocytoma and giant cell tumor usually affects adults and exhibit solid, rather
than plexiform or nestlike pattern.(1) Fibrous histiocytoma also shows a more
storiform pattern and may exhibit xanthoma cells and siderphages.(1) Fibrous
hamartoma usually occurs in the first 2 years of life and does not contain multinucleated
giant cells.(1) It has dense fibroblastic trabeculae and mature fat with a cellular
myxoid component.1 Plexiform neurofibroma demonstrates positivity for S-100 protein.1
Giant cell form of malignant fibrous histiocytoma and giant cell tumor of tendon
sheath usually shows cellular pleomorphism and giant cells with abnormal nuclei
and in most cases, affects older patients.1
Treatment: Biologic behavior is not correlated with any specific
clinical or histologic finding.( 1) Since recurrence is unpredictable, but reported
to be as high as 40%,(4) the treatment for atypical plexiform fibrohistiocytic
tumors is surgical excision (wide excision preferable to local), with frequent
interval monitoring for local recurrence and for metastasis to the lymph nodes.(1-6)
X-ray irradiation and has also been reported as an adjunct to surgical therapy
in recurrent cases.4 Chemotherapy has also been reported to be used after radical
lymph node dissection in one 5 year old girl, with no evidence of pulmonary metastasis
10 months later. (1)
1. Enzinger FM, Zhang R. Plexiform fibrohistiocytic tumor presenting in children and young adults. An analysis of 65 cases. Am J Surg Pathol. 1988; 12:818-26.
2. Fisher C. Atypical plexiform fibrohistiocytic tumor. Histopathology. 1997;30(3):271-3.
3. Giard F, Bonneau R, Raymond GP. Plexiform fibrohistiocytic tumor. Dermatologica. 1991; 183:290-3.
4. Hollowood K, Holley MP, Fletcher CDM. Plexiform fibrohistiocytic tumor: clinicopathological, immunohistochemical, and ultrastructural analysis in favour of a myofibroblastic lesion. Histopathology. 1991; 19: 503-13.
5. Herring SM. Plexiform fibrohistiocytic tumor of skin. Ann Plast Surg. 1993; 30: 459-61.
6. Ruboyianes JM, Lando M, Ciofalo L. Pathologic quiz case 2. Plexiform fibrohistiocytic tumor. Arch Otolaryngol Head Neck Surg. 1993; 119: 904-6.