Perianal Rhabdomyosarcoma: Report of a Case in an Infant and Review of the Literature

Abstract

Abstract:  Rhabdomyosarcoma of the perianal and perineal region is a rare sarcoma of childhood with a poor prognosis. The clinical findings are similar to those of condyloma accuminata, which makes it difficult to diagnose. There are a few reports of this disease in the dermatologic literature. We present a 15-month-old girl with a polypoid anal mass diagnosed as embryonal rhabdomyosarcoma and a review of the current literature.

Although rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents, there are few reports in the dermatologic literature (1). The sites most commonly affected by RMS are the head and neck region, genitourinary tract, and extremities. Rhabdomyosarcoma presenting in the perianal and perineal region is uncommon and may lead to diagnostic problems (2). Here, we present a 15-month-old girl with a polypoid anal mass diagnosed as embryonal RMS and highlight the current literature on the recent findings.

Case report

A 15-month-old girl presented with a rapidly growing asymptomatic perianal mass that her mother had noticed 3 months before admission to the hospital. After seeing a pediatric surgeon, the patient was referred to our dermatology department, and an excisional biopsy was performed. The presumed diagnosis was condyloma accuminata. The lesion was completely excised, but there was a recurrence within 2 weeks. At the second admission, the patient presented with two rapidly growing masses in the perianal region. Her medical history and clinical examination were unremarkable except postterm birth.

Physical examination revealed two skin-colored polypoid masses 2 × 2 cm and 3 × 2 cm in diameter surrounding the anal canal. These tumoral masses, which had multiple foci of hemorrhage, infiltrated the surrounding soft tissues (Fig. 1). A tender, fixed lymph node 1 cm in diameter was present in the left inguinal region.

Figure 1.  Tumoral masses in the perianal region.

Histopathologic examination revealed a neoplastic infiltration consisting of tumor cells with large pleomorphic nuclei diffusely distributed in myxoid stroma under the epithelium. Some of the the tumor cells were spindle shaped (Fig. 2A). Immunohistochemical examination showed cells that stained positively with vimentin and desmin. S-100 and CD-99 were negative (Fig. 2B). Ki-67 proliferative index was 80% (Fig. 2C).

Figure 2.  (A) Neoplastic infiltration by tumor cells with large pleomorhic nuclei in myxoid stroma (hematoxylin and eosin, ×40). (B) Positive reaction of tumor cells with desmin (original magnification ×20). (C) Staining by Ki-67 proliferation index (original magnification ×20).

In the light of these findings, this patient was diagnosed with embryonal type RMS. Thoracic, abdominal, and pelvic computed tomography examinations showed no evidence of metastasis. Consultation was held with the pediatric surgery department, and surgical treatment was not planned because of the difficulty of reconstruction of the anal region. The patient was referred to the pediatric oncology department, where she received vincristine, adriamycine, and cyclophosphamide chemotherapy.

Discussion

Rhabdomyosarcoma is a soft tissue sarcoma with striated muscle differentiation encountered most frequently in infants and children. These tumors are biologically heterogenous, and patient outcome depends on the location of the primary tumor, the extent of the disease, histopathologic pattern, and the age of the patient.

Rhabdomyosarcomas are rarely reported in the dermatologic literature. Only 2% of the RMSs are located in the perianal or perineal region (1,2). Because perianal or perineal RMS has a less favorable prognosis than RMS in other locations, the location of the primary tumor is of paramount importance in RMS. Patients with perianal or perineal RMS have a high incidence of regional lymph node involvement (3). Our case had inguinal lympadenopathy, but we could not perform histopathologic examination of the lymph node because a second operation was not planned because of the rapid recurrence of the tumor and the difficulty of the surgical procedure.

The Intergroup Rhabdomyosarcoma Study Group has categorized RMS into four groups based on the amount of residual tumor after the initial surgery (4). Our patient was evaluated as group III because the tumor recurred rapidly even though it was completely resected. Tumor size is also important. Blakely et al (3) showed that patients with tumors 5 cm or less in diameter had better prognosis. Our patient had two separate tumors with a total >5 cm.

Four main histopathologic subtypes of RMS have been defined: embryonal, alveolar, pleomorphic, and undifferentiated (1). Most perianal and perineal RMS have an alveolar histology (5). In our case, histopathologic findings were consistent with embryonal RMS. The prognosis of embryonal RMS is controversial. Although Hill et al (5) reported that this type of RMS was associated with a favorable prognosis, Uba et al (6) concluded that the embryonal type predicted an inferior outcome.

It is reported that patients younger than 10 have a better prognosis. It has been proposed that more favorable outcomes in younger patients might be related to the frequency and ease of examination of younger children by parents and pediatricians (3).

An ideal treatment of perianal RMS has not been established because of the limited number of reports. Treatment options include radical or partial surgical resection, chemotherapy, and radiotherapy (4,7), Complete tumor resection before chemotherapy should be tried, and involved lymph nodes should be sampled. The major goal in the management of perianal RMS is to preserve anal function and to achieve a tumor-free margin. Aggressive surgical intervention in the perianal region can lead to serious reconstruction problems. Radiodermatitis of the anal region may complicate radiotherapy. Because the size of the primary tumor is an important predictor of survival, surgical treatment should aim to reduce tumor size. Intensive chemotherapy and/or radiation therapy is recommended to achieve complete remission after surgical intervention (7). Our patient received multidrug chemotherapy in the pediatric oncology department after the diagnosis of RMS was established. Regression of the tumor and lymphadenopathy was observed during treatment.

Perianal or perineal RMS is a rarely seen in dermatologic practice and can present in a variety of ways. The list of differential diagnoses of perianal or perineal lesions seen in infancy and childhood is extensive. The main diseases that should be considered are perianal or perineal abscess, duplicated cyst, other soft tissue adenoma or sarcoma, condyloma lata, condyloma acuminata, and neoplasia. Hidradenitis suppurativa and Crohn’s disease may also present in the perianal region (5). Because perianal RMS commonly presents as a polypoid mass, it is most frequently misdiagnosed as perianal abscess or benign polyps (2). Perianal abscess is frequently seen in adults and may be associated with systemic signs, but anorectal sepsis is a common condition in children that usually presents as a painful mass close to the anal margin, and most cases are associated with a predisposing lesion or process. Our patient was misdiagnosed with condyloma acuminata at the first examination, indicating that RMS should be included in the differential diagnosis of tumoral lesions of childhood. Early diagnosis is essential for better prognosis (1,5). Bedause there are no standard follow-up and treatment protocols, the approach to the patient should be multidisciplinary.