Calcifying Aponeurotic Fibroma of the Chest Wall in a 5-Month-Old Infant: A Case Report and Review of the Literature

Figure 5: Cartilaginous metaplasia and collagenous stroma.

Discussion

In 1953, Keasbey [1] first described CAF in the extremities of 4 children and termed it “juvenile aponeurotic fibroma.” In 1973, Iwasaki and Enjoji [3] coined the term “calcifying aponeurotic fibroma” because the tumor was also found in adult and elderly patients. CAF is more common in male patients. It usually occurs in the distal extremities such as the palms and soles of young children, and the head, neck, and trunk are less frequently affected [2,4]. CAFalmost always appears in the first decade of life, with peak incidence from ages 8–14 years; however, cases have been reported in neonates and seniors in their 60s [5]. We performed an extensive search of the English literature and were unable to find a similar case of CAF in the chest wall.

Clinically, CAF presents as a painless, slow–growing, freely movable, firm lesion. The lesion typically ranges in size from 1–3 cm, and is often present for years before surgery. It never adheres to the overlying skin but may be attached to or infiltrate into the surrounding fasciae, tendons, aponeuroses, and periosteum [2,4,6]. While the tumor is usually asymptomatic, cases of progressive local discomfort have been reported. It has been shown that the only associated disability was limitation of motion secondary to the presence of this firm, space–occupying lesion.

On radiographs, CAF is detected as a faint radiopaque soft tissue mass, with or without small foci of stippled calcification, and there is usually no associated osseous involvement [1,6]. Radiographic features are usually inconclusive, and a CT may be helpful in the detection of calcification in cases with osseous involvement. CT is possibly of great value in differentiating CAF from periosteal chondroma or panniculitis ossificans. Magnetic resonance imaging (MRI) usually shows that the tumor has low SI on T1– and T2–WI. Sundaram et al. [8] showed that all tumors with low SI on T2–WI in their study were fibrous ones and suggested that low SI on T2–WI was indicative of marked hypocellularity and abundant fibrous elements when compared with the findings obtained for tumors with high SI on T2–WI. In addition, T2–WI with fat saturation, a technique that needs no contrast medium, is helpful for determining the extent of a lesion [9]. However, it is impossible to determine if soft tissue tumors are benign or malignant based on physical or imaging findings, and biopsy or excisional biopsy must be performed for microscopic examination [10].

Keasbey et al. described 2 phases in the development of this tumor, namely, initial phase (diffuse or florid type tumors) and late phase (compact or demarcated type tumors) [1,11]. The former is common in infants and young children, and the tumor growth is diffuse and infiltrative, with a lack of calcification. In the latter, the tumor is anodular mass with calcification and cartilage formation and with a well–defined border. This phase is frequent in adolescents and adults. However, Enzinger et al. noted that in primary or recurrent form, lesions are usually infiltrative with no evidence of the changing phases [6]. They also noted that young patients, especially those under 5 years of age, have a high risk of recurrence, based on a review of the published work [6]. Histopathological characteristics of CAF include a highly cellular architecture composed of atypical fibroblast, foci of calcification, and lesions of chondroid differentiation. Usually, the differential diagnosis includes fibrous hamartoma of infancy, diffuse infantile fibromatosis, nodular fasciitis, or infantile fibrosarcoma as a soft–tissue mass [2,4]. If calcifications or osseous defects are present in addition to the soft–tissue mass, infantile fibrosarcoma, chondroma of soft parts, and synovial sarcoma should be considered. The highly cellular architecture, locally aggressive growth pattern, and tendency to recur may lead to a misdiagnosis of sarcoma, fibrosarcoma, and pseudosarcoma followed by unnecessary amputation [4,12].

CAF frequently involves tendons, nerves, or blood vessels. The rate of local recurrence after an initial surgery has been reported to be approximately 50%; however, there is no recordof malignant transformation, with the exception of 1 case [13], metastasis, or linkage with any associated diseases. Given the poor circumscription, infiltrative growth pattern, and the high recurrence rate of approximately 50%, CAF can be mistaken for a malignant soft–tissue tumor. Therefore, pathological examination is mandatory and careful attention to the morphologic features will aid in distinguishing CAF from other soft–tissue tumors. Functional deficits are usually iatrogenic rather than the result of tumor growth or invasion. Conservative surgical management is the treatment of choice. Local excision with subsequent re–excision, if necessary, is preferred to radical tumor resection because recurrent lesions resolve spontaneously and most functional disabilities result from extended surgical resection. Complete excision with a margin of normal tissue should be performed when it is feasible to excise the tumor without compromising functionality.

To the best of our knowledge, only 14 pediatric cases have been reported in the English literature regarding CAF tumor occurrence in uncommon sites (head, face, neck, and trunk) [4,5,14,16]. There have been no reports of CAF in the chest wall. Known uncommon tumor sites, including this case, were the back in 7 cases, lumbar in 3, neck in 2, abdomen in 1, buttock in 1, and chest in 1. Of 15 patients, 10 were male and 5 were female. Patient ages ranged from 5 months to 15 years. All tumors that were surgically treated showed persistent or slowly enlarging masses, and no patient reported other clinical symptoms such as discomfort, pain, or functional compromise. The excised tumors ranged from 1.7–7 cm in size. Follow–up information was available for 8 of the 13 patients, and the follow–up period ranged from 4 months to 23 years (276 months). All CAFs had benign characteristics; however, the tumor recurred in 4 patients, with a recurrence rate of 33.3% (4 of 12 patients), and 2 of them experienced recurrences 3 or more times. A total of 9 recurrences occurred in 13 patients, but there were no deaths related to CAF recurrence or surgery. The longest time interval of tumor persistence with multiple recurrences was over 23 years. Long–term follow–up is necessary for patients with CAF because recurrence can occur even 2 decades after the initial surgery.

In conclusion, the unusual features of the present case of CAF were the young age of the patient and the uncommon occurrence site. Given the high rate of local recurrence in CAF, complete excision with a margin of normal tissue is advisable when the excision can be performed without sacrificing functionally important structures. However, it should be kept in mind that functional deficit after surgery is related to wide surgical excision, and in recurrence, re–excising a tumor is preferred to performing an extensive surgical dissection.

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