Cytologic diagnostic pitfall of dermatofibrosarcoma protuberans masquerading as primary parotid tumor: A case report

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Cytologic Diagnostic Pitfall of Dermatofibrosarcoma Protuberans Masquerading as Primary Parotid Tumor: A Case Report Neelaiah Siddaraju, M.D.,* Neha Singh, M.B.B.S., Paari Murugan, Clement D. Wilfred, M.D., Qutubuddin Chahwala, M.D., and Jayanthi Soundararaghavan, M.D.

We report the cytology of a rare case of dermatofibrosarcoma protuberans (DFSP) involving the parotid region. Our patient was a 55-year-old female who presented with a swelling in the right parotid region, which was clinically interpreted as a ‘‘recurrent parotid tumor.’’ Fine needle aspiration revealed a moderate cellular yield with spindle cell component, seen discretely as well as, embedded loosely within a fibrillary magenta matrix. A few cellular spindle cell fascicles and several discrete, naked, spindly nuclei were also noted. Neoplastic cells exhibited a minimal pleomorphism with a relatively bland chromatin and inconspicuous nucleoli. A differential diagnosis of the benign spindle cell tumor/low, or intermediate grade myxoid, spindle cell sarcomas was considered. Owing to its clinical presentation simulating a parotid tumor, possibility of ‘‘spindle cell myoepithelioma’’ was suggested. However, histopathologic examination with immunohistochemistry showed it to be a DFSP. A precise diagnosis of DFSP is not always possible on cytology alone. Owing to its location, as well as the spindle cell morphology, DFSP occurring in the parotid region is likely to be mistaken for a spindle cell myoepithelioma, in which case, an appropriate panel of immunomarkers is required for resolving the diagnostic dilemma. Diagn. Cytopathol. 2009;37:277– 280. ' 2009 Wiley-Liss, Inc. Key Words: fine needle; aspiration cytology; spindle cell tumor; dermatofibrosarcoma protuberans; myoepithelioma; spindle cell; storiform pattern; myxoid matrix

Department of Pathology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry-605 006, India *Correspondence to: Neelaiah Siddaraju M.D., Professor, Department of Pathology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry-605 006, India. E-mail: [email protected] Received 2 October 2008; Accepted 25 October 2008 DOI 10.1002/dc.21009 Published online 13 February 2009 in Wiley InterScience (www. interscience.wiley.com). '

2009 WILEY-LISS, INC.

M.D.,

Dermatofibrosarcoma protuberans (DFSP) is a slow growing tumor of intermediate malignancy which typically presents as a nodular cutaneous mass. The tumor is known for its high propensity to recur and rarely does it metastasize. The most common locations of DFSP are the extremities and the trunk; however, it may involve any site of the body. Histologically, the tumor is characterized by the typical storiform pattern.1 Fine needle aspiration cytologic findings of primary,2–4 recurrent,2,5 as well as metastatic2,6 DFSP have been described. DFSP involving the parotid region is rare; in this location, it needs to be distinguished from other spindle cell tumors, in particular of myoepithelial origin.7,8 Here, we report a case of DFSP involving the parotid region with its cytologic diagnostic pitfall.

Case Clinical Summary A 55-year-old female presented with a history of swelling in the right parotid region of 2 years duration. She gave a past history of having undergone surgery for a swelling in the same region 5 years ago. The details of surgery and the previous histopathologic report were not available. On examination, the swelling lifted the pinna of the ear and measured 7 3 5 cm; it was firm, nodular, nontender, and freely mobile. Skin was adherent to the swelling; appeared partially hypopigmented; a 3.5 cm linear scar was noted over the swelling. There was no lymphadenopathy, or any other significant findings. The clinical diagnosis was recurrent parotid tumor. Diagnostic Cytopathology, Vol 37, No 4

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Fig. 1. Slender to plump spindle cells embedded in a loose, myxoid matrix (MGG stain; 3200). [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Cytologic Findings A routine fine needle aspiration (FNA) was performed using a 23 gauge needle attached to a 10 ml syringe which yielded blood mixed particulate material. Air-dried and 95%-ethanol-fixed smears were made and stained with May–Gru¨nwald–Giemsa (MGG) and Papanicolaou techniques, respectively. Smears were moderately cellular with spindle cells, seen discretely as well as loosely embedded within a fibrillary, magenta colored, myxoid matrix (Fig. 1). Also seen were a few densely cellular tissue fragments appearing as spindle cell fascicles entangled in the blood (Fig. 2). There was a minimal pleomorphism with most cells exhibiting moderate amount of indistinct cytoplasm, spindly nuclei with bipolar tapering ends, relatively bland appearing chromatin and inconspicuous nucleoli. Discrete cells appeared as oval to spindly, and slender to plump, naked nuclei (Fig. 2, inset); occasional spindly nuclei displayed wavy nature. There was no obvious mitotic activity, or evidence of necrosis. Overall cytologic picture was that of a myxoid spindle cell tumor with the morphologic possibilities of benign neurogenic tumor, low grade malignant peripheral nerve sheath tumor (MPNST), fibromyxosarcoma, and DFSP. However, in view of the parotid location of the swelling, a diagnosis of ‘‘spindle cell myoepithelioma’’ was suggested and histopathologic examination was advised for confirmation. A wide local excision was done. Intraoperatively, the mass was found to be superficial to the masseter and mandible behind the inferior branch of the facial nerve and attached to the parotid gland.

Histopathologic Findings A nodular, skin covered surgical specimen measuring 11 3 7 3 4 cm was received in the pathology department. 278

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Fig. 2. A tissue fragment with a fascicle of slender to plump spindle cells in a hemorrhagic background (Papanicolaou stain; 3200); Inset shows discrete spindle cells seen predominantly as oval to spindly naked nuclei of varying size (Papanicolaou stain; 3200). [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Fig. 3. Histologic section of DFSP exhibiting classic storiform pattern (H&E stain; 3100). [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

The skin over the swelling appeared stretched, shiny, and hypopigmented. The actual tumor mass measured 7 3 5 3 3.5 cm with attached fibrofatty tissue and tiny strips of fascia. Cut surface was fleshy, homogenous, grayish white with shiny and slightly slimy appearance. The tissue was routinely processed and paraffin embedded; histologic sections were studied after staining with routine hematoxylin and eosin (H&E) and special stains such as van-Gieson (VG) stains. Histopathologic examination (HPE) revealed fascicles of spindle cells infiltrating in to the underlying tissue with few areas showing classic storiform pattern (Fig. 3). VG-stained section displayed variable amount of collagen deposition. Immunohistochemistry for S-100, smooth muscle actin (SMA), cytokeratin (CK), vimentin,

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DFSP MASQUERADING AS PRIMARY PAROTID TUMOR

Fig. 4. Immunohistochemistry (IHC) on histologic sections. A: Neoplastic cells of DFSP showing strong immunoexpression of CD34 (IHC stain, 3400). B: DFSP cells showing negative staining for S-100; in contrast, adipocytes in the infiltrating margin of the tumor are strongly S100 positive (IHC stain, 3400). [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

and CD34 was performed by avidin-biotin peroxidase technique. The neoplastic cells were negative for CK, S100, and SMA, whereas they expressed strong positivity for vimentin and CD34. At infiltrating margins, S-100 was strongly expressed by the normal adipocytes (Fig. 4). Based on these conclusive histologic findings, a final diagnosis of ‘‘recurrent dermatofibrosarcoma protuberans (DFSP)’’ was given.

Discussion Only rare large studies2,9 and a few case reports3–6 have dealt with the cytologic aspects of DFSP. FNA features of DFSP are known to resemble those of other low and intermediate grade spindle cell sarcomas, such as, low grade fibrosarcoma, fibromyxosarcoma, low grade MPNST as well as benign tumors such as schwannoma, nodular fasciits, and fibrous histiocytoma.9 When it occurs in rare locations such as the breast, the differential diagnosis includes lesions such as phylloides tumor and spindle cell carcinoma.4 In a parotid location, the obvious differential diagnosis to be considered is that of a spindle cell myoepithelioma.7,8 Of the larger studies on cytology of DFSP, worth mentioning, are those by Klijanienko et al.9 and Domanski et al.2 In the Klijanienko et al.,9 series of 13 cases, significant findings noted were storiform pattern, fibrillary stromal fragments, and presence of naked nuclei. Cytonuclear atypia was observed in five cases, whereas mitotic figures, mast cells, myxoid background, and dispersed adipocytes were all rare findings. Domanski et al.2 studied 13 aspirates from DFSP cases, of which only six were accurately diagnosed. Some of their diagnoses were inconclusive with respect to the benign or malignant nature of the

lesion, and two of their cases were interpreted as benign spindle cell tumors. The cytomorphologic features described in their cases were tight clusters of spindle cells embedded in a collagenous, fibrillar, and often metachromatic matrix along with dissociated, uniform or slightly atypical spindle cells, or naked nuclei.2 Similar findings have been highlighted in individual case reports.3–6 Our case presented as a recurrent parotid swelling. Spindly, and in places wavy nature of the neoplastic cells loosely embedded in a myxoid matrix, suggested a strong possibility of neurogenic tumor with a suspicion of low grade MPNST. Because of the same reasons, DFSP was also suspected, but the smears lacked typical storiform pattern. Without immunomarkers, a precise typing was difficult; however, based on the clinical presentation and diagnosis of ‘‘recurrent parotid tumor’’ as well as the spindle cell morphology of neoplastic cells in association with metachromatic matrix, a possibility of spindle cell myoepithelioma was suggested. Nonetheless, HPE with immunopositivity for vimentin and CD34 showed it to be a DFSP. Negative expression of S-100, SMA, and CK by the tumor cells convincingly excluded the possibility of neurogenic, smooth muscle and myoepithelial origin, whereas CD 34 positivity (in a tumor with storiform pattern on histologic section) firmly established the diagnosis of DFSP. In our case, the cytologic diagnosis of ‘‘spindle cell myoepithelioma’’ was considered chiefly in view of the parotid location, rather than the cytomorphologic findings alone. In this context, it is essential to know the possible cytomorphologic differences between a spindle cell myoepithelioma and DFSP. Cytologic literature on pure spindle cell myoepithelioma is sparse with only rare case reports. A case of pure spindle cell myoepithelioma, recently reported by Siddaraju et al. is of relevance here.10 That particular case of myoepithelioma showed a very high cellularity with tight spindle cell fascicles and intervening strands and globules of hyaline material; in contrast, to the present case of DFSP exhibiting a lesser cell-yield, with spindle cells, loosely embedded in a myxoid matrix. In addition, the present case of DFSP showed significant presence of individual cells, seen mainly as naked nuclei. Aspirate material of the spindle cell myoepithelioma reported by Siddaraju et al. showed a near total absence of discrete spindle cells, or naked nuclei.10 Nonetheless, as rightly emphasized by various other authors, it is not always possible on routine cytology alone to distinguish between a DFSP and other benign and low/intermediate grade spindle cell neoplasms. In such situations, as stressed by different authors, clinical assessment and the use of appropriate markers become critical for the right diagnosis.2,3 The most important marker is CD341,11 which is of importance not only in differentiating DFSP from other low grade sarcomas but also in the distinction Diagnostic Cytopathology, Vol 37, No 4

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of a DFSP from dermatofibroma. In contrast to DFSP, the benign dermatofibromas are CD34 negative.12 The other spindle cell tumor to be cytomorphologically distinguished from DFSP is hemangiopericytoma (HPC).13 The cases of HPC involving the parotid region have rarely been described.14–16 The fact that these tumors immunohistochemically simulate DFSP (with vimentin and CD 34 positivity) emphasizes the role of histologic pattern as well in their distinction.14 Histologically, HPC is characterized by the stag-horn pattern of vasculature surrounded by neoplastic cells, whereas DFSP shows distinct storiform pattern of tumor cells. On cytology, in contrast to DFSP, the fine needle aspirate in a case of HPC is often hemorrhagic that indicates its vascular nature.15 From the differential diagnostic point of view, it is worth reviewing the cytomorphology of these tumors documented in the literature. Chhieng et al.13 in their series of nine cases of HPC described cellular aspirates with discrete as well as tightly packed clusters of oval to spindle cells having uniformly sized nuclei with finely granular chromatin and inconspicuous nucleoli. The cells were found aggregated around the branched capillaries. The authors observed significant amount of basement membrane material in six of their cases and concluded that the presence of branched capillaries and abundant basement membrane material supports a diagnosis of HPC.13 Nguyen and Neifer17 in their report of two benign and one malignant HPC described similar individual cytomorphology. They also observed focal gland-like arrangement of tumor cells in some cellular areas, and benign endothelial cells were seen among the tumor cells, but not cohesive to them. The benign or malignant nature of the tumor could not be predicted in their cases.17 However, Shimizu et al.16 reported a case of malignant HPC of the parotid gland in which they described pleomorphic, hyperchromatic, elongated nuclei and a moderate amount of ill defined cytoplasm. They also described papillary arcades surrounded and encased by small oval to short spindle cells in their case.16 In the present case of DFSP, the aspirate was not highly hemorrhagic and the smears lacked the branching capillaries and the abundant basement membrane material said to be typical of HPC; therefore, its possibility was not considered. Cytogenetically, DFSP cells are characterized by supernumerary ring chromosomes composed of sequence derived from chromosomes 17 and 22, or rarely of translocations t(17;22). Ring chromosomes are observed mainly in adults, whereas translocations are encountered in pediatric patients. These gene rearrangements result in the formation of specific fusion gene COL1A1-PDGFB. This particular fusion gene has also been observed in the variants of DFSP such as giant cell fibroelastoma, Bednar tumor, adult superficial fibrosarcoma, and granular cell variant of DFSP.11

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To conclude, due to an overlapping cytomorphology of DFSP with other low/intermediate grade and benign spindle cell tumors, its precise diagnosis is not always possible merely on routine cytology. As in the present case, DFSP occurring in the parotid region is likely to be mistaken for myoepithelioma, in which case, an appropriate panel of immunomarkers helps in its precise diagnosis.

References 1. Enzinger FM, Weiss SW. Soft tissue tumors. 3rd ed. St Louis: Mosby-Year Book; 1995. p 201–225. 2. Domanski HA, Gustafson P. Cytologic features of primary, recurrent and metastatic dermatofibrosarcoma protuberans. Cancer 2002; 96:351–361. 3. Domanski HA. FNA Diagnosis of dermatofibrosarcoma protuberans. Diagn Cytopathol 2005;32:299–302. 4. Zee SY, Wang Q, Jones CM, Abadi MA. Fine needle aspiration cytology of dermatofibrosarcoma protuberans presenting as a breast mass. A case report. Acta Cytol 2002;46:741–743. 5. Filipowicz EA, Ventura KC, Pou AM, Logrono R. FNAC in the diagnosis of recurrent dermatofibrosarcoma protuberans of the forehead. A case report. Acta Cytol 1999;43:1177–1180. 6. Perry DM, Furlong JW, Johnston WW. Fine needle aspiration cytology of metastatic dermatofibrosarcoma protuberans. A case report. Acta Cytol 1986;30:507–512. 7. Wiley EL, Stewart D, Brown M, Albores Savedra J. Fibrous histiocytoma of the parotid gland. Am J Clin Pathol 1992;97:512–516. 8. Khalkhali K, Azizi MR, Atighechi S. A fibrous histiocytoma of intermediate malignancy arisen from the parotid gland. Arch Iran Med 2007;10:100–103. 9. Klijanienko J, Caillaud JM, Lagace R. Fine needle aspiration of primary and recurrent dermatofibrosarcoma protuberans. Diagn Cytopathol 2004;30:261–265. 10. Siddaraju N, Badhe B, Goneppanavar M, Mishra MM. Preoperative fine needle aspiration cytologic diagnosis of spindle cell myoepithelioma of the parotid gland. Acta Cytol 2008;52:495–499. 11. Bianchini L, Maire G, Pedeutour F. De Groupe francophone de Cytogenetique Oncologique: from cytogenetics to cytogenomics of dermatofibrosarcoma protuberans family of tumors. Bull Cancer 2007;94:179–189. 12. Akerman M, Domanski HA. Fibrohistiocytic tumors. In: Karger OSR, editor. The cytology of soft tissue tumors. monographs in clinical cytology. Vol. 16. New York; 2003. p 45–49. 13. Chhieng D, Cohen JM, Waisman J, Fernandez G, Cangiarella J. Fine needle aspiration cytology of hemangiopericytoma: a report of 5 cases. Cancer 1999;87:190–195. 14. Sawh RN, Lele SM, Borkowski J, Ventura KC, Zaharopoulos P, Logrono R. Fine needle aspiration cytology of hemangiopericytoma: report of two cases. Diagn Cytopathol 1999;21:398–401. 15. Oktem F, Karaman E, Mamak A, Yilmaz S, Erdamar S. Hemangiopericytoma of the parotid gland: a case report. Kuak Burun Bogaz Ihtis Derg 2007;17:112–115. 16. Shimizu K, OguraS , Kobayashi TK, et al. Fine needle aspiration cytology of malignant hemangiopericytoma of the parotid gland: a case report. Diagn Cytopathol 1999;21:398–401. 17. Nguyen GK, Neifer R. The cells of benign and malignant hemangiopericytomas in aspiration biopsy. Diagn Cytopathol 1985;1:327– 331.

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