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Table of Contents
CASE REPORT
Year : 2019  |  Volume : 6  |  Issue : 3  |  Page : 136-139

Myoepithelial carcinoma of soft tissue: A report of two cases


1 Department of Pathology, Armed Forces Medical College, Pune, Maharashtra, India
2 Department of Pathology, Command Hospital (Southern Command), Pune, Maharashtra, India

Date of Submission31-Jul-2018
Date of Decision27-Nov-2018
Date of Acceptance03-Dec-2018
Date of Web Publication20-Aug-2019

Correspondence Address:
Dr. Divya Shelly
Department of Pathology, Armed Forces Medical College, Sholapur Road, Pune - 411 040, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JCRP.JCRP_22_18

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  Abstract 


Primary myoepithelial neoplasms of soft tissue are rare tumors that have only recently been recognized. Due to the presence of varied architectural and cytological features both within a lesion and between different tumors, immunohistochemistry may be required to diagnose these tumors. Herein, we report two cases of myoepithelial carcinoma of soft tissue, one of whom had an aggressive clinical course.

Keywords: Immunohistochemistry, myoepithelial carcinoma, soft tissue


How to cite this article:
Balraam K V, Shelly D, Mishra PS, Sharma I, Sampath K S, Bharadwaj R. Myoepithelial carcinoma of soft tissue: A report of two cases. J Cancer Res Pract 2019;6:136-9

How to cite this URL:
Balraam K V, Shelly D, Mishra PS, Sharma I, Sampath K S, Bharadwaj R. Myoepithelial carcinoma of soft tissue: A report of two cases. J Cancer Res Pract [serial online] 2019 [cited 2019 Nov 15];6:136-9. Available from: http://www.ejcrp.org/text.asp?2019/6/3/136/264842




  Introduction Top


Primary myoepithelial neoplasms of soft tissue are rare tumors. In contrast to myoepithelial neoplasms of salivary glands, which are believed to arise from the nonductal or abluminal cells of a duct, primary myoepithelial neoplasms of soft tissue lack any normal cellular counterpart originating in soft tissue. These tumors commonly occur as subcutaneous nodules in the extremities and proximal limb girdles; however, they have also been reported in the breast, skin, and upper aerodigestive tract, albeit with lower incidence rates.[1] Due to the rarity of these tumors and diverse cytoarchitectural features, diagnosing these tumors can be challenging. Various architectural patterns have been reported in these tumors, including solid sheets, reticular, trabecular, lobular, alveolar, and pseudoacinar. The tumor cells can be epithelioid, spindle, plasmacytoid, or clear and can show a variable degree of cytological atypia.[2] Cytologic atypia is the sole criterion for malignancy in soft tissue, in contrast to invasion in the salivary glands.[2] Due to the rarity of these tumors and limited available data in the literature, the management of myoepithelial carcinoma of soft tissue is difficult. Herein, we present two cases of myoepithelial carcinoma of soft tissue: one arising in the popliteal fossa of a young female and the other arising in the upper back of an elderly female.


  Case Reports Top


Case 1

A 29-year-old female presented with complaints of a palpable mass in the right popliteal fossa for the past 1 year with no antecedent history of trauma. There was a deep-seated, solitary, ill-defined, mildly tender swelling on the medial and anterior aspect of the lower part of the right thigh which was firm to hard and fixed to the underlying structures. Ultrasonography revealed a 4 cm × 3 cm lobulated and well-encapsulated hypoechoic space-occupying lesion in the upper medial compartment of her right leg. Contrast-enhanced computed tomography revealed a 40 mm × 41 mm × 19 mm well-circumscribed mildly hypodense lesion with loss of fat plane with the underlying muscle.

Fine-needle aspiration cytology (FNAC) of the mass was done, which revealed a highly cellular smear composed of discohesive pleomorphic plasmacytoid and epithelioid cells arranged in sheets with irregular nuclear membranes, open nuclear chromatin, and multiple prominent nucleoli. Brisk mitotic figures were noted; however, no acini formation was seen. The provisional diagnosis on FNAC was of a high-grade malignancy.

An excisional biopsy from the mass revealed an infiltrating tumor [Figure 1]a, [Figure 1]b, [Figure 1]c arranged in mixed growth patterns including nested and trabecular and sheets. The tumor cells were epithelioid to ovoid with a moderate amount of pale eosinophilic to clear cytoplasm, vesicular nuclei, and prominent nucleoli. Occasional foci of plasmacytoid cells were noted arranged in a background of myxoid stroma. The tumor showed brisk mitotic activity (25–30 per 10 high-power fields [hpf]). Foci of hyalinized stroma and necrosis were also evident. No ductal differentiation was seen. On immunohistochemistry (IHC) [Figure 1]d and [Figure 1]e, the tumor cells were diffusely positive for cytokeratin (CK), epithelial membrane antigen (EMA), S-100p, vimentin, glial fibrillary acidic protein (GFAP), calponin, and p63. However, the cells were negative for smooth muscle actin (SMA), desmin, CD31, CD34, gross cystic disease fluid protein 15 (GCDFP-15), estrogen receptor (ER), T, and HMB-45, with a positive expression of INI1/SMACRB1. The MIB-1 labeling index was 50% in the highest proliferating area [Figure 2]a. Based on the histological and immunohistochemical findings, a diagnosis of myoepithelial carcinoma of soft tissue was made.
Figure 1:(a-c) Hematoxylin and eosin staining showing the tumor arranged in lobules and composed of cells with pale to clear cytoplasm in a background of chondromyxoid stroma (black arrow) (×200). (d and e) The tumor cells showed diffuse positivity for S-100p (d) and cytokeratin immunostaining (e) on immunohistochemistry (×200). (f) Postoperative magnetic resonance imaging revealing a residual lesion near the knee joint (red arrowhead) and a mass in the femoral region (red arrow)

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Figure 2: (a) MIB-1 labeling index of 50% (×400) and (b) MIB-1 labeling index of 20% (×400)

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A postoperative positron emission tomography scan and magnetic resonance imaging (MRI) revealed a residual metabolically active lesion in the subcutaneous plane on the posteromedial aspect of the right knee joint with a small mass in the right femoral region (? likely nodal mass) [Figure 1]f. Completion surgery was carried out and the residual excised lesion was sent for histopathological evaluation. The results revealed similar histomorphology and immunoreactivity; however, the resection was R1 (microscopic residual tumor). The nodal spread was evident in one of the femoral triangle lymph nodes; however, the right inguinal and iliac group of lymph nodes did not show any metastatic deposits. In view of the R1 resection, above-the-knee amputation was suggested to the patient; however, she was unwilling to proceed. The case was discussed in a multidisciplinary meeting and she was offered radiotherapy. However, she succumbed to her illness within 1 month of starting radiotherapy, as the disease had already spread to the regional lymph nodes at the time of diagnosis.

Case 2

A 60-year-old female presented with recurrent swelling in her right upper back for the past 6 years. She had undergone surgery for the swelling 10 years previously; however, no documentation was available. The swelling was 8 cm × 5 cm in size with well-defined margins, firm in consistency, and reduced mobility. The overlying skin showed a healed surgical scar. MRI revealed multiple discrete, conglomerated, lobulated mass lesions in the right posterior triangle region involving the trapezius muscle with subcutaneous extension. Fine-needle aspiration from the lesion revealed a cellular smear comprising monomorphic spindle cells along with stromal fragments. She underwent an excisional biopsy, and intraoperative findings of the lesion revealed a multilobulated, dumbbell-shaped soft-tissue tumor with areas of myxoid degeneration.

A histopathological examination of the resected specimen [Figure 3]a, [Figure 3]b, [Figure 3]c, [Figure 3]d showed a tumor arranged in lobules characterized by spindled to epithelioid cells in a background of the chondromyxoid matrix. Foci of high-grade areas were seen in the form of solid sheets of tumor showing moderate nuclear atypia and 6–8 mitotic figures per 10 hpf. No ductal differentiation was seen. On IHC [Figure 3]e and [Figure 3]f, the tumor cells were positive for EMA, p63, S-100p, calponin, and GFAP and negative for desmin, HMB-45, CD99, brachyury, and SMA. The INI1/SMACRB1 expression was retained by the tumor cells. The MIB-1 labeling index was 20% [Figure 2]b. This patient is currently being followed up and has been disease free for the past 4 months.
Figure 3: (a-c) Hematoxylin and eosin staining showing the tumor arranged in lobules in a background of abundant chondromyxoid stroma (×200). (d) This tumor showed focally high-grade morphology (inset showing sheets of cells with moderate amounts of cytoplasm, vesicular chromatin, and prominent nucleoli; ×400). (e and f) The tumor cells showed diffuse positivity for S-100p (e) and cytokeratin immunostaining (f) on immunohistochemistry (×200)

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  Discussion Top


Primary myoepithelial tumors (myoepithelioma and myoepithelial carcinoma) are rare soft-tissue tumors which primarily occur in subcutaneous tissue. They affect males and females equally over a wide age range, with a peak incidence between the third and fifth decades of life. Approximately 20% of cases occur in pediatric patients, in whom they are frequently malignant.[3] Approximately 70% of cases occur in the soft-tissue region, with the remainder being found in cutaneous areas, viscera, and bones.[4] Very few studies are available on the demographic and clinical data of this tumor. Studies have shown that margin status is strongly associated with the incidence of local recurrence. As many as 50% of cases develop metastasis to distant organs, usually at a median interval of around 2 years after the initial diagnosis.[3] Our two cases of myoepithelial carcinoma occurred in the popliteal fossa and neck region, respectively, which are known but rare sites of these tumors.

Like its counterpart in the salivary gland, cytoarchitectural heterogeneity is the hallmark of these tumors which exhibit a varied arrangement of tumor cells, namely nests, sheets, cords, reticular, and trabeculae. Within these patterns, the cells also display wavering cytomorphology in the form of epithelioid, spindled, clear, or plasmacytoid appearance in a variable amount of hyalinized or myxoid stroma.[5] The criteria used to diagnose myoepithelial carcinoma are the presence of moderate-to-severe nuclear atypia and the presence of mitotic activity and necrosis.[5] Myoepithelial carcinoma usually shows coarse or vesicular chromatin, prominent nucleoli, anisokaryosis or nuclear pleomorphisms, and brisk mitosis.[1]

Due to the varied architectural and cytological features, the differential diagnosis of these tumors is broad and includes malignant melanoma, extraskeletal mesenchymal chondrosarcoma, metastatic carcinoma, epithelioid malignant peripheral nerve sheath tumor, proximal-type epithelioid sarcoma, and poorly differentiated synovial sarcoma.

IHC may be required to rule out these differentials and prove the myoepithelial lineage [Table 1]. A literature review showed very diverging results in terms of immunoreactivity. Hornick and Fletcher[1] reported that 93% of myoepithelial carcinomas in their study were positive for CK, 63% were positive for EMA, and 87% were positive for S-100p. Similarly, they found positivity for myogenic markers including calponin (86%). Rekhi et al.[6] reported that 83% of tumors in their study were positive for EMA, 25% were positive for CK, 70% were positive for p63, 100% were positive for calponin and vimentin, and 85% were positive for S-100p. Both of these studies concluded that a combination of epithelial markers, including EMA and CKs, along with S-100p or GFAP constituted the optimal IHC panel to support a diagnosis of myoepithelial tumors. In the current study, the tumors showed reactivity to CK, EMA, S-100p, p63, vimentin, and calponin in the first case and positivity to EMA, GFAP, p63, calponin, and S-100p in the second case. EWSR1 gene rearrangement has been reported in 45% of all myoepithelial tumors,[6] and partner fusion genes have been reported to include PBX1 and ZNF444.[4],[7],[8] The diagnosis of myoepithelial tumors typically requires characteristic morphology along with an exhaustive immunohistochemical panel while confirmation of EWSR1 gene rearrangement may be helpful in certain contexts.
Table 1: Differential diagnosis of myoepithelial carcinoma of soft tissue

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Complete excision with clear free margins is the mainstay of treatment. In case of histopathologically involved margin status and/or nodal deposits, postoperative radiotherapy has been advocated.[9] In Case 1 in our report, the patient already had regional lymph node involvement at the time of histopathological diagnosis, and the surgical margins of the excised specimen were also positive for the tumor. Although the patient was offered above-the-knee amputation, she refused. She was offered radiotherapy as an alternative option; however, she died within a month of commencing radiotherapy.


  Conclusion Top


Myoepithelial carcinoma of soft tissue is a relatively rare tumor. As the tumor exhibits varying morphology, it becomes even more difficult to diagnose without the help of IHC. A correct diagnosis is required to allow for aggressive treatment whenever malignancy is suspected, as unfamiliarity with this entity can lead to an erroneous diagnosis and potentially fatal outcomes due to inadequate therapy.

Acknowledgment

The authors would like to acknowledge the laboratory technical staff in working relentlessly and with dedication and utmost sincerity.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Hornick JL, Fletcher CD. Myoepithelial tumors of soft tissue: A clinicopathologic and immunohistochemical study of 101 cases with evaluation of prognostic parameters. Am J Surg Pathol 2003;27:1183-96.  Back to cited text no. 1
    
2.
Fletcher CD, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone. 4th ed. Lyon: IARC Press; 2013.  Back to cited text no. 2
    
3.
Gleason BC, Fletcher CD. Myoepithelial carcinoma of soft tissue in children: An aggressive neoplasm analyzed in a series of 29 cases. Am J Surg Pathol 2007;31:1813-24.  Back to cited text no. 3
    
4.
Antonescu CR, Zhang L, Chang NE, Pawel BR, Travis W, Katabi N, et al. EWSR1-POU5F1 fusion in soft tissue myoepithelial tumors. A molecular analysis of sixty-six cases, including soft tissue, bone, and visceral lesions, showing common involvement of the EWSR1 gene. Genes Chromosomes Cancer 2010;49:1114-24.  Back to cited text no. 4
    
5.
Swain N, Kumar SV, Pathak J, Patel S. Soft tissue myoepithelial carcinoma of neck: A rare case report with review of the literature. J Oral Maxillofac Surg Med Pathol 2014;26:580-4.  Back to cited text no. 5
    
6.
Rekhi B, Sable M, Jambhekar NA. Histopathological, immunohistochemical and molecular spectrum of myoepithelial tumours of soft tissues. Virchows Arch 2012;461:687-97.  Back to cited text no. 6
    
7.
Brandal P, Panagopoulos I, Bjerkehagen B, Heim S. T (19;22)(q13;q12) translocation leading to the novel fusion gene EWSR1-ZNF444 in soft tissue myoepithelial carcinoma. Genes Chromosomes Cancer 2009;48:1051-6.  Back to cited text no. 7
    
8.
Brandal P, Panagopoulos I, Bjerkehagen B, Gorunova L, Skjeldal S, Micci F, et al. Detection of a t (1;22)(q23;q12) translocation leading to an EWSR1-PBX1 fusion gene in a myoepithelioma. Genes Chromosomes Cancer 2008;47:558-64.  Back to cited text no. 8
    
9.
Neto AG, Pineda-Daboin K, Luna MA. Myoepithelioma of the soft tissue of the head and neck: A case report and review of the literature. Head Neck 2004;26:470-3.  Back to cited text no. 9
    


    Figures

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