29 November 2006 – Case of the Week #65
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We thank Dr. Ronald M. Angeles, University of Pittsburgh, Pennsylvania (USA), for contributing this case. We invite you to contribute a Case of the Week by sending an email to NPernick@PathologyOutlines.com with microscopic images (any size, we will shrink if necessary) in JPG or GIF format, a short clinical history, your diagnosis and any other images (gross, immunostains, EM, etc.) that may be helpful or interesting. We will write the discussion (unless you want to), list you as the contributor, and send you a check for $35 (US) for your time after we send out the case. Please only send cases with a definitive diagnosis.
Case of the Week #65
A 37 year old woman had a wrist mass that was clinically thought to be a lipoma.
The spindle cells had diffuse cytoplasmic immunoreactivity for CD68 and calponin, and were negative for S100 and pan-keratin. CD34 highlighted the blood vessels.
What is your diagnosis?
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Nodular fasciitis of the wrist
Nodular fasciitis is a common lesion that typically presents with a history of a rapidly growing mass on the flexor forearm, chest or back. It can also develop within the bladder (Hinyokika Kiyo 1994;40:427), breast (Breast 2005;14:384), vulva (Int J Gynecol Path 1997;16:117), vagina, cervix or prostrate. There is often a history of trauma. It is frequently misdiagnosed as sarcoma based on its cellularity, the presence of mitotic figures and its rapid growth.
It typically is 2 cm or less in size and relatively well circumscribed. It is highly cellular and composed of plump, immature fibroblasts or myofibroblasts, with a feathery pattern due to the abundance of ground substance. The tumor cells usually have prominent nucleoli. There is often a myxoid stroma, frequent mitotic figures but no atypical forms, a lymphocytic infiltrate and red blood cell extravasation. The vasculature is usually prominent. There may be bands of collagen similar to keloid scars, or metaplastic bone.
The fibroblasts and myofibroblasts are typically immunoreactive for smooth muscle actin, muscle specific actin and calponin (Am J Dermatopathol 2006;28:105). Macrophages are CD68+, as are some fibroblasts that have acquired phagocytic properties. Immunostains for S100, keratin and CD34 (Am J Surg Path 1993;17:1039) are typically negative.
The differential diagnosis includes fibromatosis, fibrous histiocytoma and malignant fibrous histiocytoma. Fibromatosis is usually a large lesion that infiltrates surrounding soft tissue. Tumor cells are spindled and separated by abundant collagen. Fibrous histiocytoma is usually dermal based and has a storiform pattern. There are also prominent xanthoma cells and often Touton giant cells. Myxoid MFH has tumor cells with more pleomorphism, and often has regular arborizing vessels. There are often atypical mitotic figures, and areas of classic MFH.
Nodular fasciitis is a benign, reactive process, and excision is almost always curative, even if the lesion is incompletely excised.
Additional references: Weiss: Enzinger and Weiss’s Soft Tissue Tumors; 2001 (4th Ed)
Nat Pernick, M.D., President
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