Journal of Dr. NTR University of Health Sciences

: 2013  |  Volume : 2  |  Issue : 1  |  Page : 52--54

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

Correspondence Address:
Nitin Chawla
124/7, Rajender Nagar, Street 4, Lane 8, Dehradun, Uttarakhand


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.

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;2:52-54

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Chawla N, Reddy SJ, Agarwal M. Proliferative myositis: A case report and review of literature. J NTR Univ Health Sci [serial online] 2013 [cited 2021 May 11 ];2:52-54
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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}{Figure 2}{Figure 3}{Figure 4}


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]


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