Pathology Quiz Case: 22 year old with a supraclavicular mass

A 22-year-old female presents with a 4-month history of a 2 cm mass in her right supraclavicular region. She states that she had a cough and fatigue at the time, but no other URI symptoms at onset. She attributes her fatigue to staying up late studying. She denies any trauma and has not tried any treatments, including antibiotics.

She denies night sweats, fever, chills, weight loss, generalized pruritus or lymphadenopathy in other areas of her body. She denies any voice change, dysphagia, odynophagia, hoarseness, hemoptysis, hematemesis or weight loss. Her family history is positive for breast cancer in her mother and she is a lifelong nonsmoker.

Physical exam reveals palpable non-tender, freely movable mass in the right supraclavicular region. Palpation of the parotid, submandibular glands and thyroid gland does not reveal any suspicious masses or tenderness. No mucosal lesions, scars or masses were found on intraoral examination, with clear oropharynx. CT performed revealed a 2.0 cm right supraclavicular mass just anterior and superior to the right subclavian vein with central patches of hypoattenuation. [Figure 1]

Figure 1. Ultrasound guided FNA.

Initial ultrasound guided FNA performed was non-diagnostic. Subsequent ultrasound guided core needle biopsy on supraclavicular aspirate showed a benign spindle cell proliferation arranged in a tissue-culture like pattern with a myxoid to collagenous stroma. Immunohistochemical stains demonstrate the cells to be positive for actin and negative for cytokeratin and S100 protein. [Figures 2-3]

Figure 2. CT.

Figure 3. Immunohistochemical Stain: 10× magnification.

What is your diagnosis?

Nodular Fasciitis of the Omohyoid Muscle

First described in 1955 by Konwaler et al., nodular fasciitis is a rapidly growing benign soft tissue mass characterized by abundant cellularity, rapid growth, and high mitotic activity. Located in either the deep subcutaneous tissues or superficial fascia, nodular fasciitis is a non-neoplastic proliferation of fibroblasts and myofibroblasts. Although the pathological and clinical presentation resembles malignant soft tissue sarcomas, often leading to misdiagnosis, the condition is benign. The etiology of nodular fasciitis is uncertain, with some proposing it as a reactive process associated with trauma while others describe it as a self-limiting clonal process with neoplastic origins (Botton et al, 2006). Originally titled pseudosarcomatous fibromatosis, other titles such as nodular pseudosarcomatous fasciits, pseudosarcomatous fasciitis, infiltrative fasciitis or proliferative fasciitis may be used to refer to the same disease process.

Nodular fasciitis preferentially affects adults (80%) usually within the first 2-4 decades of life with a slight male predominance (Allen, 1972). Although rare in children, it can present as a chest wall tumor in children (1.8% of all childhood solid chest wall tumors (Suh et al, 2014)) and should be kept in consideration. After surgical excision, local recurrence has been documented but is rare (Bemrich-Stolz et al, 2010).

The majority of lesions are subcutaneous and circumscribed, lending them amenable to biopsy or excision. Patients notice a rapidly growing subcutaneous painless mass over the course of 3-6 weeks. Masses are solid, nodular, firm or rubbery and usually plateau at 2-3 cm in size, rarely exceeding 4 centimeters. The upper extremities are the most common area of presentation, especially the flexor aspect of the forearm. They are less frequently found on the trunk (20%), head and neck (20%), and lower extremities (13%) (Allen, 1972), and may have an associated history of trauma (Shimizu et al, 1984). In the head and neck region, lesions are often found on the neck or face, and less rarely on the forehead/scalp regions or around the eyes (Allen, 1972).

Histologically, nodular fasciitis demonstrates non-neoplastic proliferation of fibroblasts and myofibroblasts, although there is vast array of presentation pattern. The cellular composition of the mass can further divide nodular fasciitis into three subtypes: type 1 (myxoid), type 2 (cellular) and type 3 (fibrotic). (Shimizu et al, 1984). The subtype of nodular fasciitis diagnosed may be dependent on the duration the lesion has been present, as fibrotic type may represent the most mature and longest lasting lesions. Shimizu et al, 1984

• Type 1 myxoid variant has fibroblast-like cells within a stroma rich in collagen and/or myxoid ground substance. This type tends to form a large tumor, occurs more frequently in older patients and appears similar to the myxoid variant of malignant fibrous histiocytoma.

• Type 2 cellular nodular fasciitis has significantly less ground substance and stroma, with large plump fibroblast-like spindle cells that have vesicular nuclei. The high cellular proliferation and mitotic activity most closely resembles sarcomatous lesions.

• Type 3 fibrous type most closely resembles other benign lesions and have more spindle-shaped, slender fibroblast-like cells and increased collagen production. (Shimizu et al, 1984)

The tumor's rapid presentation and histological profile closely resembles sarcomas, often leading to misdiagnosis. Beyond sarcomas, other pathological processes to consider include neurofibromas, palmer fibromatosis, extra-abdominal desmoid tumors, and early presentation of myositis ossificans if intramuscular.

The diagnosis can be confirmed by fluorescence in situ hybridization using a probe to the USP6 17p13 locus. (Oliveira 2004) USP6 rearrangements in 10% or greater lesional cells are considered positive with a sensitivity and specificity of 90% and 100% respectively. Our patients show a USP6 rearrangement in 44% of lesional cells, confirming the diagnosis.

Imaging with ultrasound may show ill-defined hypoechoic nodules in the deep or superficial fascial layers, while imaging with MRI showed T1 isointense nodules and T2 hyperintense nodules. (Khuu et al, 2014). However this utility is limited, and fine needle biopsy or core biopsy may reveal more detailed histological findings. An initial observation period of several weeks may be warranted, especially considering the self-limiting/spontaneous regression course of the disease. Steroid injections have also been found to aid lesion regression. However, surgical excision still remains the mainstay treatment of choice. Lesions will rarely reoccur after excision.

Figure 4. Immunohistochemical Stain: 40× magnification.