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| CASE REPORT |
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| Year : 2013 | Volume
: 2
| Issue : 1 | Page : 52-54 |
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Proliferative myositis: A case report and review of literature
Nitin Chawla1, Sangireddy Jayabhaskar Reddy1, Mukesh Agarwal2
1 Department of Histopathology, VIMTA Labs Ltd., Hyderabad, India
2 CRL, VIMTA Labs Ltd., Hyderabad, India
| Date of Web Publication | 13-Mar-2013 |
Correspondence Address:
Nitin Chawla
124/7, Rajender Nagar, Street 4, Lane 8, Dehradun, Uttarakhand
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2277-8632.108515
Proliferative myositis is a benign, reactive, pseudosarcomatous fibroblastic proliferation associated with bizarre giant cells resembling ganglion cells. It is most commonly seen in 5 th decade of life. It is a skeletal muscle counterpart of proliferative fasciitis, which clinically and histologically resembles it. It most commonly affects skeletal muscles of shoulder, thorax, and thigh. Trauma is considered to be most common etiological factor. Grossly, it presents as a discrete solitary nodular mass with irregular margins measuring 1-6 cm in size. Histopathological examination of tissue shows sheets of myofibroblasts amixed with large cells, which resemble ganglion cells. Immunohistochemical evaluation of the tissue shows positivity for vimentin and SMA and negativity for desmin in myofibroblasts, whereas ganglion cell-like cells are focally positive for SMA. We report a case of proliferative myositis in a 42-years-old female patient who presented with a slow-growing, painless, irregular swelling in left forearm 3 cm below the elbow. Keywords: Myositis, proliferative, pseudosarcomatous
How to cite this article:
Chawla N, Reddy SJ, Agarwal M. Proliferative myositis: A case report and review of literature. J NTR Univ Health Sci 2013;2:52-4 |
| Introduction | |  |
Proliferative myositis is a pseudosarcomatous, benign, fibroblastic proliferation with atypical giant cells resembling ganglion cells. It is a rapidly growing lesion and infiltrates skeletal muscles in diffuse manner. [1] It is a skeletal muscle counterpart of proliferative Fasciitis, which arises from superficial fascia and is relatively superficial in location. It most commonly affects skeletal muscles of shoulder, thorax, and thigh; however, it has been reported in many uncommon sites such as tongue and oral cavity. [2],[3],[4] Majority of the patients are over the age of 45 years, but it may be seen in children also. [5] It can be easily misdiagnosed with rhabdomyosarcoma and ganglioneuroblastoma, especially in younger age group. It is usually diagnosed on histopathology, as clinical findings are non-specific. Immunohistochemistry is useful in confirming the diagnosis. [2],[6]
| Case Report | | |
A 42-years-old female patient presented with history of an irregular swelling measuring 3 × 2 × 2 cm on the left forearm 3 cm below the elbow joint for last one month. The swelling was slow-growing, firm, irregular, and painless. There was no significant injury received by her at that site before the onset of swelling. The skin overlying the lump was within normal limits. The lesion was excised and sent for histopathological examination to our lab. Grossly, the tissue showed multiple grey-white to grey-brown fragments altogether measuring 2.5 × 2 × 2 cm. Histopathological examination of tissue showed a poorly circumscribed lesion composed of fibroblasts along with bizarre giant cells resembling ganglion cells. There were few skeletal muscle fibers seen, and these fibroblasts were appearing to be arising from or infiltrating into them. A provisional diagnosis of proliferative myositis was offered [Figure 1]. Immunohistochemical examination was performed with vimentin, smooth muscle actin (SMA), and desmin using anti vimentin V-9 clone (Biogenex), anti-SMA 1A4 clone (DAKO), and anti-desmin 33 clone, respectively. Vimentin and SMA were found to be strongly positive [Figure 2] and [Figure 3], whereas desmin was negative [Figure 4] confirming the diagnosis. | Figure 1: Photomicrograph showing diffuse proliferation of fibroblasts with atypical ganglion-like cells and few skeletal muscle fibers (Right side top). (H and E, x200)
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 | Figure 2: Photomicrograph showing fibroblasts and ganglion-like cells strongly positive for vimentin; skeletal muscle fibers are negative for vimentin. (Vimentin, x100)
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 | Figure 3: Photomicrograph showing fibroblasts and occasional ganglion-like cells positive for SMA. (SMA, x100)
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 | Figure 4: Photomicrograph showing fibroblasts and ganglion-like cells negative for desmin; skeletal muscle fibers show strong positivity. (Desmin; x100)
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| Discussion | | |
Proliferative myositis is a self-limiting, benign, reactive process, which is probably preceded by some type of muscular injury, resulting in proliferation of myofibroblasts. However, history of preceding injury is present only in very few cases, thus raising the possibility of causes other than mechanical trauma for its development. In our patient, there was no history of any preceding injury for its development. [7]
Clinically, patient presents with a palpable, more or less discrete solitary nodular mass measuring 1-6 cm in diameter. The median age of occurrence is 50 years with no gender-based or race-based predilection. [1],[7] Grossly, the lesion is grey-white scar-like infiltrating into surrounding skeletal muscle fibers. [5] Histopathological examination of tissue shows a proliferation of fibroblasts surrounding individual fiber along with presence of large basophilic ganglion-like cell having vesicular nuclei and prominent nucleoli. [5] Immunohistochemical profile is similar to nodular fasciitis and proliferative fasciitis, i.e., the fibroblasts are positive for vimentin and SMA but are negative for desmin, suggesting its myofibroblastic nature. Ganglion-like cells are negative or focally positive for SMA. [6],[7],[8] In our case, the patient was a 42-years-old female with similar histopathological findings and matching immunohistochemical profile, thus confirming the diagnosis.
The differential diagnoses for the lesion are rhabdomyosarcoma and ganglioneuroblastoma. Rhabdomyosarcoma was ruled out, as ganglion-like cells were negative for desmin, whereas ganglioneuroblastoma was ruled out in view of lack of fibrillary background and SMA-negative ganglion cells. [7]
The adequate treatments for these lesions are wide local excision with minimal requirement of follow-up as the chances of recurrence are very rare. [5],[9]
| References | | |
| 1. | Kern WH. Proliferative myositis: A report of 7 cases. Arch Pathol Lab Med 1960;69:209. 
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| 2. | Enzinger FM, Dulcey F. Proliferative myositis: Report of 33 cases. Cancer 1967;20:2213.
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| 3. | Dent CD, DeBoom GW, Hamlin ML. Proliferative myositis of the head and neck. Report of a case and review of the literature. Oral Surg Oral Med Oral Pathol 1994;78:354-8.
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| 4. | Brooks JK, Scheper MA, Kramer RE, Papadimtriou JC, Sauk JJ, Nikitakis NG. Intraoral proliferative myositis: Case report and review of literature. Head Neck 2007;29:416-20.
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| 5. | Meis JM, Enzinger FM. Proliferative fasciitis and myositis of childhood. Am J Surg Pathol 1992;16:364-72.
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| 6. | Brook JS. Immunohistochemistry of proliferative myositis. Arch Pathol Lab Med 1981;105:682.
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| 7. | Weiss SW, Goldblum JR. Weiss and Enzinger Soft tissue tumors. 5 th ed. USA: Mosby; 2008. p. 192-3.
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| 8. | El-Jabbour JN, Bennett MH, Burke MM, Lessels A, O'Halloran A. Proliferative myositis- an immunohistochemcal and ultrastructural study. Am J Surg Pathol 1991;15:654-9.
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| 9. | Kent MS, Flieder DB, Port JL, Altorki NK. Proliferative myositis- a rare pseudosarcoma of the chest wall. Ann Thoracic Surg 2002;73:1296-8.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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