Volume 3, Issue 4 , Pages 188-191, December 2008
Infantile myofibromatosis: Solitary type
Article Outline
Summary
Infantile myofibromatosis is a rare tumor of childhood, which involves the head and neck region in 30% of cases. There are 3 different types: solitary, multicentric, and multicentric with visceral involvement. Herein we describe the case of a male infant with a solitary lesion in the parapharyngeal space and to our knowledge this is the first infantile myofibromatosis case in this location. Additionally, radiological and histopathological characteristics of infantile myofibromatosis are discussed in the light of the literature.
Keywords: Myofibromatosis, Neck, Solitary
1. Introduction
Infantile myofibromatosis (IM) is a rare disorder characterized by the proliferation of fibroblasts and myofibroblasts. IM is the most common fibrous neoplasm in infants, accounting for 10% of all benign head and neck tumors during infancy [1], [2]. Although it may be seen in any part of the body, it most commonly presents in the head and neck region (33% of cases).
IM was first described by Stout in 1954 as, “congenital generalized fibromatosis”. Then, in 1981 Chung and Enzinger defined the histopathological features of the disease and used the term, “infantile myofibromatosis” [3], [4]. It is seen in subcutaneous tissue, muscular structures, and, rarely, in bone tissue as single or multiple nodules. The disease has a poor prognosis when seen in the viscera. Most cases (75%) present during the first year of life [1], [5]. Herein a patient with infantile myofibromatosis involving the left parotid and parapharyngeal space is presented.
2. Case
An 11-month-old male infant presented to our clinic with swelling on the left side of the neck. The swelling was known to have been growing for about 7 months. At another center 3 months prior to presenting at our clinic, subtotal mass excision from the left neck was performed and the pathology report stated that the mass was infantile fibromatosis. On physical examination there was a surgical incision scar behind the left auricle due to the previous surgery and a non-tender swelling was palpated on the left parotid region. Facial nerve function was normal. Magnetic resonance imaging (MRI) of the neck was performed, which revealed an infiltrative, 3
cm×2cm×1.5cm lesion in the left parotid region. The lesion had mass effect on adjacent tissue. The patient was followed-up for 2 months; however, due to rapid growth of the mass surgical treatment was suggested. MRI of the neck was repeated and the finding was a mass originating from the deep lobe of the left parotid gland (compared to the previous MRI, an increase in the size of the mass was observed) (Fig. 1A and B). A modified Blair incision was used to expose the surgical field. The facial nerve and all of its branches, which were pushed laterally by the mass originating from the deep parotid lobe, were exposed (Fig. 2). The mass was also adherent to the great vessels and mastoid process. Using blunt and sharp dissection, the mass was removed from the facial nerve branches, great vessels, and the surrounding tissue. The lateral cortex of the mastoid process was destroyed by the lesion. Finally, en-bloc resection was accomplished. Gross specimen of the purple-white mass was 8cm×5cm and it was moderately stiff. Postoperatively left facial nerve paresis was observed. Postoperative pathological diagnosis of the mass was infantile myofibromatosis, solitary-type (Fig. 3, Fig. 4, Fig. 5).
Fig. 1.
MRI scan demonstrates the mass originating from the deep lobe of left parotid gland (A: axial plane; B: coronal plane).
Fig. 2.
The mass was dissected from the facial nerve with blunt and sharp dissection.
Fig. 3.
Histopathological examination revealed spindle-shaped cells with eosinophilic cytoplasm in a loose fibrous stroma containing collagen fibers (H&E stain).
Fig. 4.
Tumor cells invading vessels in some parts of the lesion.
Fig. 5.
Immunohistochemical examination: cells stained for smooth muscle actin.
The patient was followed-up clinically and with MRI. At the 2-year follow-up, no recurrence was noted and facial nerve function recovered completely.
3. Discussion
Although IM is described as a rare disorder, it absolutely must be considered in the differential diagnosis when faced with a solitary, painless, and slow-developing mass, as it is the most common type of fibromatosis and is located in the head and neck region in 33% of cases. According to our search of the medical literature, there are no reported cases of infantile myofibromatosis located in the parapharyngeal space or the parotid region, making ours the first such report. Clinically, there are 3 different IM types: solitary, multicentric, and multicentric type with visceral involvement [6]. The most common type of IM is solitary (74%), which presents as a single, well-circumscribed, slow-growing mass that feels hard with palpation. Visceral involvement is more commonly multicentric. Nevertheless, in the medical literature isolated gastrointestinal system involvement has been reported [7]. Among all cases, 54% present at the time of birth and 75% during the first year of life, and it is more commonly seen in males [1], [4], [5]. The etiology is unknown, but because there are some familial cases in the literature, it is thought that incomplete autosomal dominant or recessive inheritance might play a role [8].
The morbidity rate associated with myofibromatosis varies depending on the organ involved. In addition to infiltrating, IM pushes the adjacent tissue by mass effect. IM develops in 3 steps: (1) the tumor enlarges, if solitary, or increases in number if multicentric; (2) it remains stable; (3) spontaneous regression occurs [1], [4], [8], [9]. This regression occurs with central necrosis and increasing apoptosis of the tumor [10]. The third type of IM (multicentric type with visceral involvement) has a poorer prognosis than the other 2 types, with a rate reported to be as high as 20%.
Precise diagnosis is generally made after histopathological examination of the tumor. That is why radiological examination has only a supportive role in diagnosis. With computed tomography (CT) it is seen as a well-circumscribed and well-contrasted lesion, with soft tissue density. Necrosis and intratumoral calcification might be seen [4], [10]. The mass is observed to displace adjacent tissue and to have lytic areas on bone, with hyperostotic reaction on the surrounding bone tissue when the bone is involved. The lesion is seen as hypointense in T1-weighted and hyperintense in T2-weighted MRI [11]. In addition to this, in cases that have been diagnosed histopathologically, radiological examination prior to treatment is necessary in order to evaluate treatment response.
For precise diagnosis, excisional or incisional biopsy must be performed. According to the location of the mass and the relationship between the mass and the surrounding tissue, either excisional or incisional biopsy techniques must be used. This tumor must be histopathologically differentiated from other spindle cell fibroblastic tumors (aggressive fibromatosis, fibrosarcoma, histiocytoma, neural sheath tumors, etc.) [12]. The tumor consists of 2 different histopathological components. In the peripheral section of the tumor there are spindle cells, which make little groups resembling fibroblasts, and bigger cells resembling smooth muscle cells. In the central region less differentiated spherical cells, necrosis, calcification, and hyalinization are seen. Cells are present in a multi-directionally arranged rich collagen matrix and atypical cells cannot be seen. The tumor can be dyed with smooth muscle actin and vimentin, but cannot be dyed with S-100 and vimentin [1], [4].
The choice of the treatment and approach varies depending on the type of IM. For the solitary-type, complete excision of the tumor is curative. In this type of tumor, following complete excision there is no recurrence in 80% of cases [3]. Because of possible spontaneous regression, some surgeons offer only follow-up, especially if the patient is asymptomatic, so as not to cause unnecessary functional and cosmetic morbidity. If multiple tumors and/or visceral involvement are present, more conservative approaches are offered instead of surgical excision of the lesions [1], [7]. After complete excision of the tumor, the rate of recurrence is between 7% and 9% [1], [4]. Chemotherapy and radiotherapy have no place in the treatment of IM. To the best of our knowledge there are no published reports of the malignant transformation of IM.
As a result, following accurate histopathological diagnosis of this rare tumor, the preeminent method of treatment is surgery. While choosing the type and scale of surgery, the age of the patient and location of the tumor must be considered. Subsequently, meticulous follow-up of the patient is paramount due to the possibility of recurrence.
References
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PII: S1871-4048(08)00029-4
doi:10.1016/j.pedex.2008.04.002
© 2008 Elsevier Ireland Ltd. All rights reserved.
Volume 3, Issue 4 , Pages 188-191, December 2008
