CC BY-NC-ND
0Human Pathology: Case Reports (2014) 1, 52-57 —
Human PATHOLOGY
Case Reports
www.humanpathologycasereports.com
Mixed tumor of the soft tissue (arm)
TadashiTerada MD, PhD *
Department of Pathology, Shizuoka City Shimizu Hospital, Miyakami 1231 Shimizu-Ku, Shizuoka 424-8636, Japan Received 28 June 2014; revised 4 September 2014; accepted 18 September 2014
Keywords:
Soft tissue; Mixed tumor; Histopathology; Immunohistochemistry
Abstract Mixed tumor of soft tissue is extremely rare; only 15 cases have been reported in English literature. A 56-year-old man presented with a tumor in right arm. Physical examination showed a tumor measuring 3*3*3 cm of deep portion of right arm. MRI showed a well-defined deep tumor measuring 3*3*4 cm of arm next to fascia. The tumor was resected, and it was found that the tumor is located in deep subcutaneous tissue outside the fascia. Histologically, the tumor was well-defined and contained a fibrous capsule. The tumor cells showed no significant nuclear atypia. The tumor was composed of epithelial, myoepithelial, and stromal elements. The epithelial element formed tubules, and myoepithelial element showed solid nests and periepithelial linings. The epithelial element showed frequent apocrine features including apocrine snouts. The stromal element was composed of cartilage and myxoid tissues. Immunohistochemically, the epithelial element was positive for cytokeratin (CK) AE1/3, CK CAM5.2, CK34BE12, CK7, CK8, CK18, CK19, EMA, CEA, CD56, p53, and Ki-67 (labeling = 80%), but negative for CK5/6, CK14, CK20, vimentin, p63, S100 protein, CD10, CD34, ASMA, CD68, myoglobin, bcl-2, BMP-2, TGF-£1, CDK-4, and MDM2. The myoepithelial element was positive for CK AE1/3, CK CAM5.2, CK34BE12, CK5/6, CK7, CK8, CK14, CK18, p63, vimentin, CD10, S100 protein, bcl-2, p53, and Ki-67 (labeling = 20%), but negative for CK19, CK20, EMA, CEA, CD34, ASMA, CD68, CD56, myoglobin, BMP-2, TGF-p.1, CDK-4 and MDM2. The stromal element was positive for vimentin, S100 protein (cartilage), and Ki-67 (labeling = 6%), but negative for other antigens examined including bcl-2, BMP-2, TGF-£1, CDK-4 and MDM2. No findings of metastasis, invasion, and recurrence were recognized clinically. The author speculates that the current mixed tumor was derived from misplaced apocrine glands in the deep soft tissue. © 2014 Published by Elsevier Inc.
1. Introduction
Mixed tumor of the soft tissue is extremely rare; only 15 cases have been reported [1-4], to the best of author's knowledge. Mixed tumor is most common in major and minor salivary glands, and mixed tumor ofthese locations is
* Tel.: +81 54 336 1111; fax: +81 54 336 1315. E-mail address: piyo0111jp@yahoo.co.jp.
usually designated as pleomorphic adenoma or mixed tumor [5]. Mixed tumor is also seen in the skin, and such cutaneous mixed tumor is usually called chondroid syringoma [6]. Mixed tumor is extremely rare in the soft tissue [1-4,7]. According to WHO blue book [7], mixed tumor of soft tissue is included in a group of mixed tumor/myoepithe-lioma/parachordoma. Mixed tumor is composed of epithelial, myoepithelial, and mesenchymal cells which often show cartilage, and shows pleomorphic diverse features of
http://dx.doi.org/10.1016/j.ehpc.2014.09.004 2214-3300/© 2014 Published by Elsevier Inc.
histology [1-7]. According to WHO blue book [7], in the section of mixed tumor/myoepithelioma/parachordoma group of soft tissue, mixed tumor is used for tumor having epithelial tubular element, and myoepithelioma for tumor lacking epithelial tubular element [7]. Parachordoma is a vague entity, and should be included in mixed tumor or myoepithelioma [7]. Thus, mixed tumor and myoepithe-lioma are different histological entities [7], although the histology is mutually similar. There has been only one study of soft tissue mixed tumor with immunohistochemical study, which was performed by Kilpatrick et al. [1]. Herein reported is a case of mixed tumor of the soft tissue of arm. An extensive immunohistochemical study was performed in this case report.
2. Case report
A 56-year-old man noticed a tumor in right arm, and consulted to our hospital. Physical examination showed a deep tumor measuring 3x3x3 cm in the right arm. No other skin tumor was found. MRI showed a well-defined deep tumor measuring 3x3x4 cm of the arm next to fascia (Fig. 1). The resonance density of the tumor is heterogenous (Fig. 1). The tumor was excised. During the operation, it was found that the tumor was located in deep subcutaneous tissue next to fascia. It was not within the striated muscles. No tumor was found in the overlying skin and upper subcutaneous tissue.
02062852 i. 2012/05/15 056V *tse2d1rs7
Fig. 1 MRI findings of the right arm tumor. MRI showed a well-defined deep tumor measuring 3x3x4 cm of the arm next to fascia. The density of the tumor is heterogenous.
Histologically, the tumor was well-defined and contained a fibrous capsule (Fig. 2A). The resected section included the epidermis and dermis, and the distance between superficial part of the tumor and superficial epidermis was 12 mm. The tumor cells showed no significant nuclear atypia. The tumor showed pleomorphic diverse histologies, but basically the tumor was composed of epithelial, myoepithelial, and stromal elements (Fig. 2A and B). The epithelial element formed tubules (Fig. 2C), and myoepithelial element showed solid nests (Fig. 2D) and periepithelial linings (Fig. 2C). The epithelial element showed frequent apocrine features including apocrine snouts and ample acidophilic cytoplasm (Fig. 2E). Some areas of the myoepithelial element were composed of myoepithelial cells with clear cytoplasm. The stromal element was composed of cartilage (Fig. 2F) and myxoid tissue. There were gradual transitions between the myoepithelial element and stromal element. No apparent carcinoma areas were seen.
An immunohistochemical analysis was performed by the Envision method (Dako Corp, Glostrup, Denmark), as previously reported [8-13]. The results are shown in Table 1. Immunohistochemically, the epithelial element was positive for cytokeratin (CK) AE1/3, CK CAM5.2 (Fig. 3A), CK34BE12, CK7 (Fig. 3B), CK8, CK18 (Fig. 3C), CK19, epithelial membrane antigen (EMA) (Fig. 3D), carcinoembryonic antigen (CEA) (Fig. 3E), CD56 (Fig. 3F), p53, and Ki-67 (labeling = 80%) (Fig. 4A), but negative for CK5/6 (Fig. 4B), CK14 (Fig. 4C), CK20, vimentin (Fig. 4D), p63 (Fig. 4E), S100 protein (Fig. 4F), CD10, CD34, a-smooth muscle antigen (ASMA), CD68, myoglobin, bcl-2, bone morphogenic protein-2 (BMP-2), transforming growth factor-^1 (TGF-p>1), cyclin dependent kinase (CDK-4), and MDM2. The myoepithelial element was positive for CK AE1/3, CK CAM5.2 (Fig. 3A), CK34BE12, CK5/6 (Fig. 4B), CK7 (Fig. 3B), CK8, CK14 (Fig. 4C), CK18 (Fig. 3C), p63 (Fig. 4E), vimentin (Fig. 4D), S100 protein (Fig. 4F), CD10, bcl-2, p53, and Ki-67 (labeling = 20%), but negative for CK19, CK20, EMA (Fig. 3D), CEA (Fig. 3E), CD34, ASMA, CD68, CD56, myoglobin, BMP-2, TGF-p 1, CDK-4 and MDM2. The stromal element was positive for vimentin, S100 protein (cartilage), and Ki-67 (labeling = 6%), but negative for any types of CK, EMA, p63, CD10, CD34, CD68, p53, ASMA, CD56, myoglobin, bcl-2, BMP-2, TGF-P1, CDK-4 and MDM2. The stromal element was positive for vimentin, S100 protein (cartilage), and Ki-67 (labeling = 6%), but negative for any types of CK, EMA, p63, CD10, CD34, CD68, p53, ASMA, CD56, myoglobin, bcl-2, BMP-2, TGF-(S1, CDK-4 and MDM2.
No findings of metastasis, invasion or recurrence were noted clinically. Clinical examination identified no tumors in head and neck regions including the salivary glands and oral
Fig. 2 Histopathologic findings of the soft tissue tumor of the arm. A: Low power view. The tumor is round and well-defined. The tumor has complete capsule. The tumor is composed of cartilage, myoepithelial solid nests, and epithelial tubules. HE: x20. B: Intermediate power view. The soft tissue tumor is composed of epithelial element forming tubules (lower), myoepithelial element forming solid nests (left) and peritubular linings (lower), and stromal element including myxoid tissue (center) and cartilage (upper). HE: x 40. C: High power view of the tubular epithelial element and peritubular myoepithelial element. The epithelial cells form tubules, and myoepithelial cells are present outside the peritubular epithelial cells. HE: x200. D: Intermediate power view. The myoepithelial cells form solid cell nests. HE: x200. E: Very high power view. The tubular epithelial cells show apocrine features of apocrine snouts and acidophilic ample cytoplasm. HE: x 400. F: High power view. The stromal element shows cartilage. HE: x 200.
cavity. No skin tumor was found. The patient is now healthy and free from tumors or diseases 43 months after the operation.
3. Discussion
Mixed tumor of the soft tissue is extremely rare. The current case is the 21st case of mixed tumor of soft tissue after Kilpatrick et al. (18 cases) [1], Pauwels et al. (one case) [2], Adachi et al. (one case) [3], and Tomoeda et al.
(one case) [4] in the English literature, to the best of the author's knowledge. The current tumor was located in the deep subcutaneous tissue just adjacent to fascia. The tumor was not located in the striated muscles, and no skin tumor was found. Therefore, the present tumor is not a cutaneous tumor or a muscular tumor but a soft tissue tumor. Thus, the present tumor is not chondroid syringoma of the skin. Further, the current tumor is located in the area containing no salivary glands. Therefore, the present tumor is not pleomorphic adenoma or mixed tumor of salivary glands.
According to WHO blue book [5-7], mixed tumor (pleomorphic adenoma or chondroid syringoma) is
Table 1 Immunohistochemical findings of the present
tumor.
Antigens Epithelial Myoepithelial Stromal
element element element
CK AE1/3 +++ ++
CK CAM5.2 ++ +
CK34BE12 + +++
CK5/6 - +++
CK7 ++ +
CK8 ++ +
CK14 - +
CK18 + +
CK19 + -
CK20 - -
Vimentin - +++ ++
EMA ++ -
CEA + -
S100 protein - ++ + (cartilage)
CD10 - +++
CD56 + -
p53 + +
p63 - +++
Ki-67 LI 80% 20% 6%
CD34 - -
ASMA - -
CD68 - -
Myoglobin - -
Bcl-2 - ++
BMP-2 - -
TGFß1 - -
CDK-4 - -
MDM2 - -
CK: cytokeratin. EMA: epithelial membrane antigen. LI: labeling index,
ASMA: alpha-smooth muscle antigen. CEA: carcinoembryonic antigen.
BMP-2: bone morphogenic protein-2. TGF-beta1 transforming growth
factor-ß1. CDK4: cyclin dependent kinase.
MDM2. The myoepithelial element was positive for CK AE1/3, CK
CAM5.2 (Fig. 3A), CK34BE12, CK5/6 (Fig. 4B), CK7 (Fig. 3B), CK8,
CK14 (Fig. 4C), CK18 (Fig. 3C), p63 (Fig. 4E), vimentin (Fig. 4D),
S100 protein (Fig. 4F), CD10, bcl-2, p53, and Ki-67 (labeling = 20%),
but negative for CK19, CK20, EMA (Fig. 3D), CEA (Fig. 3E), CD34,
ASMA, CD68, CD56, myoglobin, BMP-2, TGF-ß1, CDK-4 and
MDM2. The stromal element was positive for vimentin, S100 protein
(cartilage), and Ki-67 (labeling = 6%), but negative for any types of CK,
EMA, p63, CD10, CD34, CD68, p53, ASMA, CD56, myoglobin, bcl-2,
BMP-2, TGF-ß 1, CDK-4 and MDM2.
defined as a tumor of variable capsulation characterized microscopically by architectural rather than cellular pleomorphism. Epithelial and modified myoepithelial elements intermingle most commonly with tissues of mucoid, myxoid and chondroid appearance [5-7]. The current tumor was completely encapsulated. The present tumor was composed of epithelial, myoepithelial, and stromal elements, and showed diverse and pleomorphic cellular architecture. The epithelial and myoepithelial cells
were verified by immunohistochemistry of epithelial markers such as various CK profile, EMA and CEA and by immunohistochemistry of myoepithelial markers such as CK34BE12, CK5/6, CK14, p63, S100 protein, and CD10. The stromal element of the current tumor contained myxoid tissue and cartilage. Therefore, the current soft tissue tumor is authentic mixed tumor because the current tumor fulfills the criteria of mixed tumor of WHO books [5-7]. The present tumor is not myoepithelioma of soft tissue, because the epithelial cells were present and they formed glandular structures [7]. The current mixed tumor of the soft tissue is not metastatic tumor, because careful examination of the major salivary glands, oral cavity, and skin identified no tumors. The current tumor is not malignant. No apparent carcinoma was seen, indicating the present tumor is not carcinoma ex pleomorphic adenoma (mixed tumor). The current tumor appears not to be malignant pleomorphic adenoma or mixed tumor (metas-tasizing pleomorphic adenoma), which shows benign histologic features. However, malignant mixed tumor cannot be excluded completely. The tumor-free follow-up period of 43 months in the present patient suggests the benign nature of the tumor.
The origin of mixed tumor of the soft tissue is an enigma, and no consideration has been done [1-4,7]. The rarity of cases of soft tissue mixed tumor may hinder the consideration of original cells. It is very curious that mixed tumor can arise in soft tissue devoid of epithelial cells. In the current case, apocrine features with apocrine snouts were seen in the epithelial tumor cells. The author speculates that the current mixed tumor was derived from misplaced apocrine glands in the deep soft tissue of the arm. Otherwise, pulripotential stem cells of the soft tissue might give rise to the mixed tumor of the soft tissue.
The present study employed extensive immunohisto-chemical study. The immunoprofile of mixed tumor of the salivary glands has been studied. The epithelial cells of mixed tumor of salivary glands are positive for CK3, CK6, CK10, CK11, CK13 and CK16, while the neoplastic myoepithelial cells express CK13, CK14 and CK16. These findings are somewhat different from those of the current case. It has been known that the neoplastic myoepithelial cells co-express vimentin and pan-CK and are variably positive for S100 protein, ASMA, GFAP, calponin, CD10, p63 and muscle-specific actin (HHF-35). These findings of neoplastic myoepithelial cells in mixed tumor of salivary glands are compatible with the findings of the current case. The neoplastic myoepithelial cells near the stromal element of mixed tumor express BMP [5]. However, the current mixed tumor of the soft tissue did not express BMP.
Immunohistochemical study of mixed tumor of the soft tissue has been performed only once by Kilpatrick et al. [1]. They demonstrated that mixed tumor (18 cases) and myoepithelioma (one case) of the soft tissue expressed
Fig. 3 Immunohistochemical findings. Cytokeratin (CK) CAM5.2 (A), CK7 (B), and CK18 (C) are expressed in both epithelial cells and myoepithelial cells. EMA (D), CEA (E), and CD56 (F) are expressed in epithelial cells but not in myoepithelial cells. *200.
pan-CK in 16/16, S100 protein in 16/17, ASMA in 6/14, muscle specific actin (HHF-35) in 2/10, desmin in 2/10, GFAP in 3/11, and EMA in 3/16. Immunohistochemical result of the present case (Table 1) is basically similar to the data of Kilpatrick et al. [1]. The present case of mixed tumor of the soft tissue revealed the CK immunoprofile in the epithelial and myoepithelial cells. Of interest is that CD5/6, CK34BE12, and CK14 were expressed in the myoepithelial cells but not in the epithelial cells. These types of CK are known to be expressed in myoepithelial cells. CD10 expression showed a similar pattern; CD10 is well known to be expressed in myoepithelial cells [1,10].
Vimentin, S100 protein and p63 labeled myoepithelial cells but not epithelial cells, being compatible with other study [1,5-7,10]. EMA and CEA were expressed in epithelial cells but not in myoepithelial cells. These are new findings. Expression of bcl-2 was seen in myoepithelial cells but not in epithelial cells, suggesting that bcl-2 may be a marker of myoepithelial cells. This is a novel finding. CD56 (NCAM) expression was seen in epithelial cells but not in myoepithelial cells, suggesting that epithelial cells of mixed tumor of the soft tissue show neuroendocrine features. In the present case, no ASMA expression is seen in both epithelial cells and myoepithelial cells, although ASMA is a good
Fig. 4 Immunohistochemical expressions. Ki-67 labeling is high in epithelial cells (labeling = 80%) (A). In contrast, CK5/6 (B), CK14 (C), CK20, vimentin (D), p63 (E) and S100 protein (F) are expressed in myoepithelial cells, but not in epithelial cells. *200.
marker of myoepithelial cells [5-7,10]. Expression of p53 was present in both epithelial and myoepithelial cells, suggesting that the both cell types in mixed tumor of the soft tissue have p53 gene mutations. In the current case, the Ki-67 labeling is very high (80%) in epithelial cells and relatively high (20%) in the myoepithelial cells, suggesting that both cell types have high cell proliferative activity. However, positive p53 and high Ki-67 labeling of the present case do not imply that the present tumor is malignant, because HE histology did not show malignant features. No expression of BMP-2, TGF-£1, CDK-4 and MDM2 was noted in all the three elements of the mixed tumor of the current case. BMP-2 and TGF-£ 1 play an important role in the formation of bone and cartilage. It is thought that the stromal element including myxoid tissue, cartilage and bone of mixed tumor is derived from myoepithelial cells [5-7]. The negative BMP-2 and TGF-£1 reactivities in the present mixed tumor suggest that BMP-2 and TGF-£1 are not essential in the differentiation of myoepithelial cells into bone and cartilage in mixed tumor. The negative CDK-4 and MDM2 in the current mixed tumor suggest that these oncoproteins and oncogenes do not function in the pathogenesis of mixed tumor. Myoglobin was negative in all the three elements, implying no participation of this protein in the pathogenesis of mixed tumor. In the stromal element of mixed tumor, only vimentin, S100, and Ki-67 were positive, and other antigens examined were negative, suggesting that these other antigens do not play a part in the differentiation of myoepithelial cells into the stromal element in mixed tumor of soft tissue.
In summary, the author reported an extremely rare case of mixed tumor of the soft tissue. An extensive immunohisto-chemical study was performed in the mixed tumor of the soft tissue.
The author has no conflict of interest.
References
[1] Kilpatrick SE, Hitchcock MG, Kraus MD, Calonje E, Fletcher CD. Mixed tumors and myoepitheliomas of soft tissue: a clinicopath-ologic study of 19 cases with a unifying concept. Am J Surg Pathol 1997;21:13-22.
[2] Pauwels P, Dal Cin P, Roumen R, van den Berghe H, Sciot R. Intramuscular mixed tumor with clonal chromosomal changes. Virchows Arch 1999;434:167-71.
[3] Adachi T, Oda Y, Sakamoto A, Saito T, Tamiya S, Hachitanda Y, et al. Mixed tumor of deep soft tissue. Pathol Int 2003;53:35-9.
[4] Tomoeda M, Yuki M, Kubo C, Yoshizawa H, Kitamura M, Nagato S, et al. Malignant mixed tumor of the soft tissue occurring after total knee arthroplasty. Orthopedics 2011;34:e768-71.
[5] Eveson JW, Kusafuka K, Stenman G, Nagao T. Pleomorphic adenoma. In: Barnes L, Eveson JW, Reichart P, Sidransky D, editors. World Health Organization Classification of Tumours. Pathology and genetics of head and neck tumorsLyon: IARC Press; 2005. p. 254-8.
[6] McNiff J, Vassallo C, McCalmont TH, Rosso R, Requena L, Borroni G, et al. Benign tumours with apocrine and eccrine differentiation. In: LeBoit PE, Burg G, Weedon D, Sarasin A, editors. World Health Organization Classification of Tumours. Pathology and genetics of skin tumorsLyon: IARC Press; 2006. p. 139-48.
[7] Kilpatrick SE, Limon J. Mixed tumour/myoepithelioma/parachor-doma. In: Fletcher CDM, Unni KK, Mertens F, editors. World Health Organization Classification of Tumours. Pathology and genetics of tumors of soft tissue and boneLyon: IARC Press; 2002. p. 198-9.
[8] Terada T, Kawaguchi M, Furukawa K, Sekido Y, Osamura Y. Minute mixed ductal-endocrine carcinoma of the pancreas with predominant intraductal growth. Pathol Int 2002;52:740-6.
[9] Terada T, Kawaguchi M. Primary clear cell adenocarcinoma of the peritoneum. Tohoku J Exp Med 2005;271:271-5.
[10] Terada T. Ductal adenoma of the breast: immunohistochemistry of two cases. Pathol Int 2008;58:801-5.
[11] Terada T. Gall bladder adenocarcinoma arising in Rokitansky-Schoff sinuses. Pathol Int 2008;58:806-9.
[12] Terada T. Gastrointestinal stromal tumor of the uterus: A case report with genetic analyses of c-kit and PDGFRA genes. Int J Gynecol Pathol 2009;28:29-34.
[13] Terada T. Intraductal tubular carcinoma, intestinal type, of the pancreas. Pathol Int 2009;59:53-8.
