Fine needle aspiration cytology in fibromatosis.

Fibromatosis form a spectrum of clinicopathologic entities characterized by the infiltrative proliferation of fibroblasts that lack malignant cytologic features. The fibromatosis can be localized or infiltrative and multicentric and can involve internal tissues and organs as the mesentery, retroperitoneum, breast, and almost every organ and region of the body, including the bones, the meninges and the central nervous system. We report a case of 37-year-old male who presented with a right supraclavicular mass with superficial infiltrative type of fibromatosis and fine needle aspiration cytology (FNAC) was performed. We report this case because of limited literature of FNAC in fibromatosis and quick role of FNAC in the diagnosis of fibromatosis.

Introduction

The term “Fibromatosis” encompasses a broad variety of lesions, divided into (1) superficial (fascial), (2) deep, which are musculo-aponeurotic abdominal or extra-abdominal, intra-abdominal and others involving various organs of the body and (3) fibromatosis of infancy and childhood. Characteristically, they display an infiltrative growth pattern and may recur yet never metastasize. Their biologic behavior has been described as between benign fibrous lesions and fibrosarcoma.[1] Fibromatosis can occur in any age and can involve any site. They present as nodular soft tissue masses and thus are amenable to fine needle aspiration cytology (FNAC). In cytologic smears, a spectrum of cytologic features may be seen based on the site aspirated and the phase or age of the lesion. Therefore, initial diagnosis of fibromatosis may be challenging, but recurrent lesions can aptly be spotted on FNAC. We present a case of 37-year-old male who presented with a superficial infiltrative type of fibromatosis.

Case Report

A 37-year-old male presented with the presence of a right supraclavicular mass since 20 days. It was gradually progressive, but not associated with pain or numbness. On examination, it was 3 × 3 cm in size, firm to feel and fixed to the underlying deep muscle. Adjacent vessels carotid, subclavian and brachial plexus were preserved. Magnetic resonance imaging (MRI) was performed, which showed a T1 T2 hypo-intense lesion in the inferior aspect of right supraclavicular region with focal areas of calcification. The lesion was diffusely infiltrating the adjacent soft tissue [Figure 1].

Figure 1

Magnetic resonance imaging (MRI) showing a T1 T2 hypointense lesion in the right supraclavicular region which is diffusely infiltrating the adjacent soft tissue

FNAC from the mass was performed which revealed moderately cellular smears and showed scattered spindle to fusiform cell clusters, stromal fragments [Figure 2a] and collagen matrix material. These spindle cells were embedded in or were in proximity to the densely eosinophilic collagen matrix material [Figure 2b and 2c]. The cells were oval to spindle shaped with tapering ends, bipolar nuclei, bland nuclear chromatin and inconspicuous nucleoli [Figure 2d]. Based on the morphology a cytologic diagnosis of spindle cell lesion possibly benign was offered. Histopathological examination of the mass confirmed the diagnosis of fibromatosis. The patient had recurrence of the same lesion after one year and nine months. FNAC from the recurrent lesion confirmed it to be the same lesion.

Figure 2

Cytology smears showing fibromatosis; (a) Bland spindle cells embedded in hypocellular dense stromal fragment (H and E, ×200); (b) Spindle cells seen within stromal fragments (H and E, ×200); (c) Oval to spindle cells embedded in metachromatically staining matrix material (MGG, ×400); (d) Oval to spindle cells with bland nuclear chromatin and inconspicuous nucleoli (H and E, ×400)

Discussion

Fibromatosis constitutes a broad spectrum of fibrous proliferation with similar histologic appearances. It can be localized or infiltrative and multicentric and can involve internal tissues and organs as the mesentery and the retroperitoneum (often associated with familial intestinal polyposis), the breast, and almost every organ or region, including bones, meninges and central nervous system.[12] A number of classification schemes have been proposed for fibromatoses based on location, histologic appearance and age of the patient. Based upon the location, these are divided as superficial and fascial, which include palmer, planter and penile fibromatoses and those which are deep and musculo-aponeurotic include abdominal and intra-abdominal fibromatoses.[1] Based on the age, they are classified into congenital and acquired types. Based on histologic appearances, these may be classified into three phases: proliferative, involutive and residual. There are few cases series[34] as well as case reports of FNAC in fibromatoses, which includes cases of fibromatosis colli, infantile myofibromatosis and fibromatosis of breast.[5-7] FNAC from fibromatoses may yield a spectrum of cytologic findings. Depending upon the age and location of the lesion, different cytologic features may be present ranging from the cellular, mildly atypical aspirate mimicking low grade sarcoma to acellular benign appearing aspirate that can be seen in superficial fibromatosis.[8] In such cases, the aspirate should be more vigorous as the dense connective tissues are not easy to sample by fine needle. Two to three passes should be taken in different directions to avoid the same track and to obtain adequate cellularity.

The differential diagnosis of fibromatoses ranges from a reactive fibrous lesions secondary to inflammation to a low grade fibrosarcoma. This includes scar or keloid, mesenchymal repair, nodular fasciitis, schwannoma, leiomyoma, solitary fibrous tumor (SFT), gastrointestinal stromal tumor (GIST), fibrosarcoma, synovial sarcoma and malignant melanoma.[910] Extensive sampling from various sites is recommended to differentiate these entities. Malignant tumors such as fibrosarcoma display increased cellularity, cytologic atypia and mitosis, which may overlap with features of proliferative phase of fibromatosis.[1] The nuclei in a schwannoma are wavy and serpentine in contrast to plump nuclei of fibromatosis. Aspirates of leiomyoma are usually paucicellular and have cells with blunt or cigar-shaped nuclei. Hemosiderin granules are usually associated with myofibroblastic cells. Scars are less cellular than fibromatoses. In mesenchymal repair, the number of stromal cells is less than those observed in fibromatosis, the cells display more stellate configurations and a greater degree of inflammation may be noted.[1] Nodular fasciitis also show limited cellularity with a background of inflammatory cells.

Deep fibromatosis shows a strong nuclear positivity for β-catenin immunostaining, which can be of help in differentiating it from other myofibroblastic proliferations. β-catenin reactivity is also seen in SFT, endometrial stromal sarcoma and synovial sarcoma. SFT is also known to be positive for CD34 and CD99. Smooth muscle neoplasms are positive for desmin and majority of GIST show positivity for c-kit. Therefore, cell block may be obtained from the aspirated material and the recommended panel includes at least β-catenin, c-kit, CD34 and desmin to differentiate fibromatosis from other entities with morphologic overlaps.[3]

FNAC is useful in providing a tentative pathologic diagnosis of these tumor-like lesions, which under the appropriate clinical setting can be used for management, if surgical intervention is contraindicated or not warranted. Based on clinical history, physical findings, radiological data and cytologic observations, a correct diagnosis can be rendered in most cases.