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Presented by Dr. Justin Bishop and prepared by Dr. Jason Kern.
Case 2: A 15 year old boy presents with a rapidly growing neck mass.
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1. Question
Week 618: Case 2
A 15 year old boy presents with a rapidly growing neck mass.
Correct
Answer: Nodular Fasciitis
Histology: The lesion consists of a relatively well circumscribed proliferation of spindled cells. The lesional nuclei are elongated and hypochromatic. Extravasated red blood cells are prominent, and focal hyalinized, keloidal-like collagen is seen. Some mitotic figures are seen, but atypical mitoses are absent.
Discussion: Nodular fasciitis is a proliferation of fibroblasts and myofibroblasts that classically presents as a rapidly growing mass in the upper extremities or head and neck. A subset of cases have a history of preceding trauma. While classically thought of as a non-neoplastic, reactive proliferation, recent studies have shown a consistent fusion of the non-muscle myosin (MYH9) gene with the USP6 oncogene, suggesting that it is a benign self-limiting neoplasm. NF is benign; excision is curative and some cases resolve spontaneously.
Histologically nodular fasciitis is well circumscribed, and architecturally displays a haphazard, vaguely storiform, or “S-shaped” pattern of growth. NF consists of irregular, short fascicles of plump myofibroblasts with an appearance similar to those of granulation tissue (i.e., “tissue culture”-like). Cytologically, the myofibroblasts are bland and lack pleomorphism. The nuclei are hypochromatic and vesicular, with smooth nuclear contours and delicate nucleoli (Figure 11). The mitotic rate in NF is often high, a potentially alarming feature, but atypical mitoses are not seen. Lymphocytes, giant cells, and especially extravasated red blood cells are often intermixed with the spindled cells. Microcysts and microscopic areas of hemorrhage are common. Depending on the age of the lesion, NF varies from myxoid to fibrotic; the stages of evolution often coexist in the same lesion, imparting a “zoned” pattern.
In the differential diagnosis, sarcomas typically arise deeper in the soft tissue, and are often larger and more infiltrative than nodular fasciitsi. At the microscopic level, sarcomas usually have a more organized architectural pattern, and display overtly malignant cytologic features (e.g., nuclear pleomorphism, hyperchromasia, atypical mitotic figures, necrosis). A benign entity to consider in the differential diagnosis is fibromatosis. However, fibromatosis is more deep-seated and infiltrative, and grows in broad fascicles with prominent-appearing vessels. If there is doubt, nuclear expression of beta-catenin confirms the diagnosis of fibromatosis.
Incorrect
Answer: Nodular Fasciitis
Histology: The lesion consists of a relatively well circumscribed proliferation of spindled cells. The lesional nuclei are elongated and hypochromatic. Extravasated red blood cells are prominent, and focal hyalinized, keloidal-like collagen is seen. Some mitotic figures are seen, but atypical mitoses are absent.
Discussion: Nodular fasciitis is a proliferation of fibroblasts and myofibroblasts that classically presents as a rapidly growing mass in the upper extremities or head and neck. A subset of cases have a history of preceding trauma. While classically thought of as a non-neoplastic, reactive proliferation, recent studies have shown a consistent fusion of the non-muscle myosin (MYH9) gene with the USP6 oncogene, suggesting that it is a benign self-limiting neoplasm. NF is benign; excision is curative and some cases resolve spontaneously.
Histologically nodular fasciitis is well circumscribed, and architecturally displays a haphazard, vaguely storiform, or “S-shaped” pattern of growth. NF consists of irregular, short fascicles of plump myofibroblasts with an appearance similar to those of granulation tissue (i.e., “tissue culture”-like). Cytologically, the myofibroblasts are bland and lack pleomorphism. The nuclei are hypochromatic and vesicular, with smooth nuclear contours and delicate nucleoli (Figure 11). The mitotic rate in NF is often high, a potentially alarming feature, but atypical mitoses are not seen. Lymphocytes, giant cells, and especially extravasated red blood cells are often intermixed with the spindled cells. Microcysts and microscopic areas of hemorrhage are common. Depending on the age of the lesion, NF varies from myxoid to fibrotic; the stages of evolution often coexist in the same lesion, imparting a “zoned” pattern.
In the differential diagnosis, sarcomas typically arise deeper in the soft tissue, and are often larger and more infiltrative than nodular fasciitsi. At the microscopic level, sarcomas usually have a more organized architectural pattern, and display overtly malignant cytologic features (e.g., nuclear pleomorphism, hyperchromasia, atypical mitotic figures, necrosis). A benign entity to consider in the differential diagnosis is fibromatosis. However, fibromatosis is more deep-seated and infiltrative, and grows in broad fascicles with prominent-appearing vessels. If there is doubt, nuclear expression of beta-catenin confirms the diagnosis of fibromatosis.
