Parotid Gland Nodular Fasciitis: A Clinicopathologic Series of 12 Cases with a Review of 18 Cases from the Literature

Abstract

Nodular fasciitis (NF), very uncommon in the parotid gland, is a benign myofibroblastic proliferation that may be mistaken for other neoplastic proliferations. The mass-like clinical presentation and histologic features result in frequent misclassification, resulting in inappropriate clinical management. There are only a few reported cases in the English literature. Cases within the files of the authors' institutions (retrospective) confined to the parotid gland were compared to cases reported in the English literature (Medline 1966-2014). The patients included five females and seven males, aged 11-70 years (mean 45.2 years). All patients presented with a mass lesion, present on average 1.9 months, without a documented history of trauma. The lesions were 0.7-5.2 cm (mean 2.2 cm). Seven patients had fine needle aspiration. The majority of the lesions were circumscribed (n = 9), composed of spindle-shaped to stellate myofibroblasts (MF) arranged in a storiform growth pattern, juxtaposed to hypocellular myxoid tissue-culture-like areas with extravasation of erythrocytes. Dense, keloid-like collagen (n = 7) and occasional giant cells were seen (n = 6). Mitotic figures (without atypical forms) were readily identifiable (mean 4/10 HPFs). By immunohistochemical staining, the MF were reactive with vimentin, actins, and calponin, while the histiocytes were reactive with CD68. All patients had surgical excision. One patient developed local recurrence (12 months later). All were alive and disease free at last follow-up, with a mean 133 months of follow-up. The principle differential diagnoses include fibrosarcoma, fibromatosis, pleomorphic adenoma, myoepithelioma, neurofibroma, schwannoma, solitary fibrous tumor, leiomyoma, fibrous histiocytoma and myxoma. NF of the parotid gland occurs in middle-aged patients who present with a mass (mean 2.2 cm) in the parotid gland of short duration (1.9 months). FNA misinterpretation frequently leads to excision. Separation from myoepithelial and mesenchymal lesions affecting the parotid gland results in appropriate management.

Nodular fasciitis: A frequent diagnostic pitfall on fine‐needle aspiration

“…This latter point is supported further by the fact that only a minority of cases were definitively described as benign. The literature has addressed many instances of the misclassification of NF as a malignant lesion . However, we would like to point out that failing to call NF benign still may prompt unnecessary surgical excision.…”

“…Nodular fasciitis (NF) is a benign, self‐limited fibroblastic/myofibroblastic proliferation most commonly occurring in the upper extremities (volar aspect of the forearm), trunk, and back in adults. However, numerous additional locations have been described, including the parotid gland, external ear, oral cavity, and breast . Furthermore, children most commonly develop lesions in the head and neck region .…”

“…Although the clinical course of NF is completely benign and typically regresses within a few months without surgery or treatment of any kind, it can be very challenging diagnostically, often mimicking a malignant process due to its rapid growth clinically and its high cellularity, mitotic activity, and variable/nonspecific cytomorphologic findings . In fact, NF is frequently misclassified as malignant, leading to unnecessary surgery and patient distress . Conversely, mistaking a malignant process for NF can lead to mismanagement and the delay of treatment.…”

Nodular fasciitis, a forgotten entity

“…Involvement of the head and neck has been more commonly observed in children. Cases with rare tumor locations, such as the lower female genital tract, bladder, prostate, tongue, and parotid gland, have been reported …”

“…Remarkably, in spite of the high number of mitotic figures, atypias are rare. Histologically, nodular fasciitis is classified into three subtypes: myxoid or reactive (type I), cellular (type II), and fibrous (type III); however, the lesions may present characteristics of different subtypes, corresponding to progressive phases of the same disease . Histological characteristics of cases 2 and 4 were compatible with myxoid or reactive subtype, while cases 1 and 3 showed features of the cellular pattern.…”