Journal of Cytology
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CASE REPORT  
Year : 2013  |  Volume : 30  |  Issue : 1  |  Page : 71-73
Cytomorphology of pleomorphic fibroma of skin: A diagnostic enigma


1 Department of Pathology, Integral Institute of Medical Sciences and Research, Lucknow, India
2 Department of Pathology, C.S.M. Medical University (erstwhile KGMC), Lucknow, India
3 Department of Pathology, VMMC and Safdarjung Hospital, New Delhi, India

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Date of Web Publication21-Feb-2013
 

   Abstract 

Pleomorphic fibroma (PF) is a benign, polypoid, or dome-shaped cutaneous neoplasm with cytologically atypical fibrohistiocytic cells. We describe the cytomorphological features of PF retrospectively with histopathological diagnosis in a 38-year-old male who presented with 3 × 1.5 cm swelling in the soft tissues of the thigh for 6 months. This lesion is benign despite the presence of pleomorphic or bizarre cells. We review the differential diagnosis of PF with other mesenchymal tumors. To the best of our knowledge, cytomorphological features on fine needle aspiration cytology of this tumor are not yet documented in literature.

Keywords: Fine needle aspiration cytology; pleomorphic cells; pleomorphic fibroma

How to cite this article:
Yadav Y K, Kushwaha R, Sharma U, Gupta K. Cytomorphology of pleomorphic fibroma of skin: A diagnostic enigma. J Cytol 2013;30:71-3

How to cite this URL:
Yadav Y K, Kushwaha R, Sharma U, Gupta K. Cytomorphology of pleomorphic fibroma of skin: A diagnostic enigma. J Cytol [serial online] 2013 [cited 2014 Oct 31];30:71-3. Available from: http://www.jcytol.org/text.asp?2013/30/1/71/107525



   Introduction Top


Pleomorphic fibroma (PF) of the skin is a rare benign fibrous tumor. [1] The lesion is usually polypoid, located in the dermis, and is formed by coarse collagen bundles with sparse cells. It is also characterized by the presence of marked cellular atypia and pleomorphism without mitosis. [1] We describe the cytomorphological features on fine needle aspiration (FNA) smears of a histologically and immunohistochemically proven case of PF. Cytomorphological features on FNA of this tumor are not well documented in literature.


   Case Report Top


A 38-year-old male presented with a superficial, painless, polypoidal, soft tissue mass since 6 months, measuring about 3 × 1.5 cm in size, and involving the back of the thigh. Fine needle aspiration cytology (FNAC) was done and slides were stained with Giemsa stain. The aspirate yielded cellular smears. Background showed metachromatic stromal fragments. Cells were pleomorphic having very large nuclei (monster cells) with scanty cytoplasm. Few of the nuclei showed single nucleoli [Figure 1]. Nuclear membranes frequently showed notches, creases, or folds. Cells were lying singly and occasionally forming clusters. These were admixed with the spindle cell component along with few multinucleated cells. Necrosis and mitotic figures were not seen in smears. On FNA, the swelling was diagnosed as fibrohistiocytic lesion with atypical cells and the mass was subsequently excised.
Figure 1: Cellular smears containing pleomorphic cells having very large nuclei (monster cells) with scanty cytoplasm. Few of the nuclei revealing nucleoli (Giemsa, × 400)

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On gross examination, the mass was well circumscribed measuring 3 × 1.5 cm. The cut section was solid, grayish-white, and fibrous. Routine processing and hematoxylin and eosin staining were done. Microscopically, tumor showed thick bundle of haphazardly arranged collagen in the dermis. Spindle- and irregularly shaped stellate or multinucleate cells were scattered between the collagen bundles. These cells were markedly atypical showing scant cytoplasm and large, pleomorphic, enlarged hyperchromatic nuclei with small nucleoli [Figure 2]. No mitosis or necrosis was evident in multiple sections examined. Based on these features, diagnosis of PF was made.
Figure 2: Section showing pleomorphic cells scattered between the collagen bundles (H and E, × 200)

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Immunoprofile of lesional cells revealed positive staining for vimentin [Figure 3] and CD34 and negative staining for S-100.
Figure 3: Lesional cells revealed positive staining for vimentin (IHC, × 200)

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   Discussion Top


PF of skin was first described by Kamino et al., in 1989. [1] PF is a benign fibrous lesion which is located mainly in the lower extremities, followed by trunk, head, and neck and rarely in the subungual region. Most of these lesions occur in adults, with a peak incidence in the fifth decade of life. [1]

Role of FNAC in diagnosis of soft tissue tumor has been fairly documented as well as debated but the cytomorphological features on FNAC of PF are not yet documented in literature. [2] In contrast to the histological findings (which is hypocellular), the FNA smear in our case was cellular. Majority of cells were pleomorphic with very large nuclei like monster cells of dermatofibroma and few of them possessed single nucleolus. Nuclear membrane showed notches, creases, or folds. Few cells were multinucleated. Cells were having scanty cytoplasm or were devoid of cytoplasm. Small fragments of metachromatic stroma were present in the background representing collagen bundles. Necrosis and mitotic figures were not seen in the smears. Thus, on FNA, PF can easily be misdiagnosed as malignant soft tissue tumor because it contains bizarre pleomorphic cells showing considerable atypia. This lesion has been shown to be benign despite the presence of pleomorphic or bizarre cells, although lesion may locally recur when incompletely excised. [1] This also reveals the importance of mitosis and necrosis in making a diagnosis of malignant soft tissue tumor on cytology, as both these features were not seen in this tumor.

Histological examination of PF of the skin reveals a dermal tumor with striking nuclear atypia. The neoplastic cells show large pleomorphic and hyperchromatic nuclei with small nucleoli. In addition to these mononuclear cells, the atypical nuclear features can also be observed in multinucleated giant cells. [1],[3] Degeneration, ischemia, or the paracrine influence of mast cells may create the cytological atypia in PF. [1],[4],[5] Two variants have been described: Myxoid and sclerotic. [6],[7] In fact, some investigators have postulated that the PF of the skin is actually a variant of the sclerotic fibroma. [4],[8] Other researchers have called these as pleomorphic sclerotic fibromas. [9]

Lesional cells in PF are always positive for vimentin and negative for S-100 and cytokeratin. Positive expression of muscle-specific actin, CD34 and rarely alpha-1 antichymotrypsin, has also been observed. [1],[3],[4],[8],[9],[10]

The cytological differential diagnosis of PF of skin has not been discussed in literature. However, histological differential diagnosis includes: Atypical fibroxanthoma, dermatofibroma with monster cells, giant cell fibroblastoma, desmoplastic Spitz nevus, and desmoplastic melanoma. [1],[3],[9],[10]

In our case, bundles of collagen were present with low cellularity, thus ruling out atypical fibroxanthoma and dermatofibromas with atypical or monster cells. Dermatofibromas with atypical or monster cells also contains foam cells and hemosiderin-laden macrophages which were not seen in our case. Giant cell fibroblastoma resembles PF as both contain atypical fibroblastic cells. Giant cell fibroblastoma is usually seen in childhood and is characterized by infiltrative growth and features sinusoidal structures lined by atypical cells, whereas our case was an adult without infiltrative growth and sinusoids. Desmoplastic Spitz nevus and desmoplastic melanoma show some areas of melanocytic differentiation and cells are positive for S-100 protein, both these features were absent in our case. Thus, the final diagnosis of PF was made.

Thus, from a clinical as well as pathological standpoint, recognition of a benign lesion of this type is very important since an incorrect cytological interpretation could result in inappropriate treatment.

 
   References Top

1.Kamino H, Lee JY, Berke A. Pleomorphic fibroma of the skin: A benign neoplasm with cytologic atypia. A clinicopathologic study of eight cases. Am J Surg Pathol 1989;13:107-13.  Back to cited text no. 1
    
2.Willén H, Akerman M, Carlén B. Fine needle aspiration (FNA) in the diagnosis of soft tissue tumours; a review of 22 years experience. Cytopathology 1995;6:236-47.  Back to cited text no. 2
    
3.Hsieh YJ, Lin YC, Wu YH, Su HY, Billings SD, Hood AF. Subungual pleomorphic fibroma. J Cutan Pathol 2003;30:569-71.  Back to cited text no. 3
    
4.García-Doval I, Casas L, Toribio J. Pleomorphic fibroma of the skin, a form of sclerotic fibroma: an immunohistochemical study. Clin Exp Dermatol 1998;23:22-4.  Back to cited text no. 4
    
5.Pitt MA, Roberts IS. Myxoid cutaneous pleomorphic fibroma. Histopathology 1994;25:300.  Back to cited text no. 5
    
6.Miliauskas JR. Myxoid cutaneous pleomorphic fibroma. Histopathology 1994;24:179-81.  Back to cited text no. 6
    
7.Martín-López R, Feal-Cortizas C, Fraga J. Pleomorphic sclerotic fibroma. Dermatology 1999;198:69-72.  Back to cited text no. 7
    
8.Mahmood MN, Salama ME, Chaffins M, Ormsby AH, Ma CK, Linden MD, et al. Solitary sclerotic fibroma of skin: A possible link with pleomorphic fibroma with immunophenotypic expression for O13 (CD99) and CD34. J Cutan Pathol 2003;30:631 - 6  Back to cited text no. 8
    
9.Chen TM, Purohit SK, Wang AR. Pleomorphic sclerotic fibroma: A case report and literature review. Am J Dermatopathol 2002;24:54-8.  Back to cited text no. 9
    
10.Rudolph P, Schubert C, Zelger BG, Zelger B, Parwaresch R. Differential expression of CD34 and Ki-M1p in pleomorphic fibroma and dermatofibroma with monster cells. Am J Dermatopathol 1999;21:414-9.  Back to cited text no. 10
    

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Correspondence Address:
R Kushwaha
Department of Pathology, C.S.M. Medical University (erstwhile KGMC), Lucknow
India
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DOI: 10.4103/0970-9371.107525

PMID: 23661949

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