Malignant fibrous histiocytoma of the scalp: A rare differential with a dramatic clinical presentation.

Malignant fibrous histiocytoma (MFH) a pleomorphic sarcoma of uncertain origin was first described by O'Brien and Stout in 1964. It is the most common primary soft tissue sarcoma of late adult life; its occurrence is rare in the pediatric population. MFHs are commonly known to arise in the extremities and the trunk although it can occur almost anywhere in the body. MFH of the scalp is extremely rare; moreover, there is paucity of literature with regards to prevalence of scalp and skull neoplasms. We present an unusual case of a primary MFH involving the scalp of a 5-year-old child and discuss its unusual clinical presentation, histology with immunohistochemistry correlation and its management. Reviewing the literature of primary MFH of the scalp, our patient to the best of our knowledge, is probably the youngest case reported so far.

INTRODUCTION

The differential diagnosis of paediatric skull and scalp lesions is broad and includes congenital, inflammatory, traumatic and neoplastic lesions. Neoplasms of the scalp and skull in children comprise a heterogeneous assemblage which is quite different from that seen in adults. Most of the paediatric scalp and skull neoplasms are benign.[1] The incidence of malignant neoplasms in the scalp and scalp ranges from 0 to 7.7%, a great majority of them are in fact believed to be metastatic rather than primary neoplasms.[23] Malignant fibrous histiocytoma (MFH) is the most common primary soft tissue sarcoma of late adult life and its occurrence is rare in the pediatric population. We present an unusual case of a primary MFH involving the scalp of a 5-year-old child and discuss its unusual clinical presentation and its management. Reviewing the literature of primary MFH of scalp, our patient, to the best of our knowledge, is probably the youngest case reported so far.

CASE REPORT

A 5-year-old girl child was brought to our centre by her caretakers for an increasing soft tissue swelling involving the right temporal region of her scalp for just about a year. Her neonatal, immunization and past medical histories were normal. Clinical examination revealed a 10 × 8cm soft tissue swelling, which was fixed to the underlying right temporal bone. The summit of the swelling showed a 6 × 4 cm necrotic ulcer with scabbing and occasional serous discharge. The swelling extended 3 cm lateral to the lateral canthus of the right eye in its medial aspect and was seen displacing the right pinna downwards in its inferior aspect. [Figure 1] A Computerized Tomography (CT) scan of the head and neck revealed the large extra cranial well enhancing soft tissue mass in the right temporal region which was seen eroding both the outer and the inner tables of the right temporal bone, but without any intra-dural or intracranial extension. [Figure 2] A trucut biopsy from the lesion suggested a diagnosis of a high grade MFH. A CT scan of the chest was normal and so were other hematological and biochemical parameters. She was taken her for an upfront radical surgery which entailed an enbloc wide excision of the tumor along with the underling temporal bone. The resultant soft tissue and bony defect was reconstructed by a scalp rotation flap and a skin graft to cover the donor site. [Figure 3a–d] The final histopathology revealed a fleshy tumor measuring 10 × 8.5 × 8cm which on microscopy revealed a tumor consisting of sheets and fascicles of oval to spindle cells with moderate cytoplasm and hyper chromatic nuclei surrounded by collegenizedstroma. Mitosis was seen in 0-2 per 10 high-power fields. Immunohistochemistry revealed immunopositivity to vimentin, smooth muscle actin, myogenin and CD68. Immunohistochemistry for keratin, desmin, CD31 and CD34 were negative. 40% of the tumor cells showed nuclear positivity for Ki-67. The final diagnosis with immunohistochemistry correlation was that of a spindle cell sarcoma high grade consistent with a MFH. [Figure 4a–d] The patient was offered adjuvant radiotherapy but her caretakers were not keen on the same. She is presently disease free for close to a year following her surgery.

Figure 1

Clinical photograph at presentation

Figure 2

Axial Computerized Tomography scan of the head and neck revealing the large extra cranial well enhancing soft tissue mass in the right temporal region which was seen eroding the right temporal bone

Figure 3

a: Intra operative photograph following wide excision of the tumor, (bc) Specimen photograph showing the fleshy tumor excised with wide margins, (d) Post operative clinical photograph following reconstruction with the local rotation flap

Figure 4

(a) H and E x 20- Tumor consisting of sheets and fascicles of oval to spindle cells with moderate cytoplasm and hyper chromatic nuclei surrounded by collegenisedstroma, (b) IHC X 40-Tumor cells showing immunopositivity to vimentin, (c) IHC X 40-Tumor cells showing immunopositivity to CD 68, (d) IHC X 40-40% Tumor cells showing immunopositivity to Ki-67

DISCUSSION

MFH is a pleomorphic sarcoma of uncertain origin and is reported to be the most common soft-tissue sarcoma in adults with a peak incidence in the seventh decade. Rhabdomyosarcomas are in fact the most common soft tissue sarcoma in children. Non-rhabdomyosarcoma soft tissue sarcomas which include MFH are a heterogeneous group of tumors, accounting for only about 3% of all childhood malignancies.[4]

MFH is commonly known to arise in the extremities and the trunk although it can occur almost anywhere in the body because of its mesenchymal origin.[5] There is paucity of literature with regards to the prevalence of scalp and skull neoplasms both in children and in adults. In a review of 75 pediatric patients with scalp and skull lesions, the common pathologic entities were langerhans cell histiocytosis, epidermal cysts, epidermoid/dermoids, hemangiomas, and neurofibromas, in descending order.[6]

The presenting symptoms of the various scalp and skull lesions are quite similar, regardless of the primary pathology. The most common presenting complaint is a visible or palpable mass or an ulcerated nodule. MFH typically exhibits a broad range of diversity in its histopathological appearances and has been classified into five subtypes: storiform-pleomorphic, giant cell, inflammatory, myxoid and angiomatoid types.[7] The tumor subtype in our patient was storiform-pleomorphic, which accounts for up to 70% of all the reported cases.

The approach to the management of MFH in children, being rare is by and large extrapolated from the adult experience.[89] Surgery in the form of wide excision is the primary modality of management of MFH.[3] Adjuvant radiotherapy and chemotherapy have been used either alone or in various combinations in an attempt to better the survival outcomes; however, no firm conclusions can be drawn with regards to their effectiveness.[4] They have been more commonly used in patients with large unresectable tumors and in the setting of metastatic disease.

The tumor cells in MFH have a tendency to grow along facial planes, thus making them more prone for local recurrences; involvement of the skeletal muscle heightens the chances of local recurrences from 27% to about 43%. Metastatic disease has been reported in 0-43% of the pediatric MFH and 5-41% of adult MFH, the most common site of metastasis being the lung (90%), followed by lymph nodes, (35%) bones (8%) and liver (1%).[4] The adverse prognostic factors include high histological grade, tumor size of >5cm and deep seated tumors.[10] Interestingly the survival rates in children with MFH is better than that in their adult counterparts.[4]

In conclusion, a primary MFH should to be considered as a rare differential in the evaluation of pediatric skull and scalp lesions; such a clinical scenario warrants an aggressive surgical approach with selected use of adjuvant therapies and a prolonged surveillance.